-<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+ "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
- <title>Stacker: An Example Of Using LLVM</title>
+ <title>Stacker: An Example Of Using LLVM</title>
<link rel="stylesheet" href="llvm.css" type="text/css">
</head>
<body>
+
<div class="doc_title">Stacker: An Example Of Using LLVM</div>
-<hr>
+
<ol>
<li><a href="#abstract">Abstract</a></li>
<li><a href="#introduction">Introduction</a></li>
<li><a href="#gep">The Wily GetElementPtrInst</a></li>
<li><a href="#linkage">Getting Linkage Types Right</a></li>
<li><a href="#constants">Constants Are Easier Than That!</a></li>
- </ol>
- </li>
+ </ol></li>
<li><a href="#lexicon">The Stacker Lexicon</a>
<ol>
- <li><a href="#stack">The Stack</a>
- <li><a href="#punctuation">Punctuation</a>
- <li><a href="#comments">Comments</a>
- <li><a href="#literals">Literals</a>
- <li><a href="#words">Words</a>
- <li><a href="style">Standard Style</a>
- <li><a href="#builtins">Built-Ins</a>
- </ol>
- </li>
+ <li><a href="#stack">The Stack</a></li>
+ <li><a href="#punctuation">Punctuation</a></li>
+ <li><a href="#comments">Comments</a></li>
+ <li><a href="#literals">Literals</a></li>
+ <li><a href="#words">Words</a></li>
+ <li><a href="#style">Standard Style</a></li>
+ <li><a href="#builtins">Built-Ins</a></li>
+ </ol></li>
<li><a href="#example">Prime: A Complete Example</a></li>
<li><a href="#internal">Internal Code Details</a>
<ol>
<li><a href="#tests">Test Programs</a></li>
<li><a href="#exercise">Exercise</a></li>
<li><a href="#todo">Things Remaining To Be Done</a></li>
- </ol>
- </li>
+ </ol></li>
</ol>
-<div class="doc_text">
-<p><b>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> </b></p>
-<p> </p>
+
+<div class="doc_author">
+ <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
</div>
-<hr>
+
<!-- ======================================================================= -->
-<div class="doc_section"> <a name="abstract">Abstract </a></div>
+<div class="doc_section"><a name="abstract">Abstract</a></div>
<div class="doc_text">
<p>This document is another way to learn about LLVM. Unlike the
<a href="LangRef.html">LLVM Reference Manual</a> or
classes were derived from the Value class. The full power of that simple
design only became fully understood once I started constructing executable
expressions for Stacker.</p>
+
<p>This really makes your programming go faster. Think about compiling code
for the following C/C++ expression: <code>(a|b)*((x+1)/(y+1))</code>. Assuming
the values are on the stack in the order a, b, x, y, this could be
expressed in stacker as: <code>1 + SWAP 1 + / ROT2 OR *</code>.
-You could write a function using LLVM that computes this expression like this: </p>
-<pre><code>
+You could write a function using LLVM that computes this expression like
+this: </p>
+
+<div class="doc_code"><pre>
Value*
expression(BasicBlock* bb, Value* a, Value* b, Value* x, Value* y )
{
- Instruction* tail = bb->getTerminator();
- ConstantSInt* one = ConstantSInt::get( Type::IntTy, 1);
- BinaryOperator* or1 =
- BinaryOperator::create( Instruction::Or, a, b, "", tail );
- BinaryOperator* add1 =
- BinaryOperator::create( Instruction::Add, x, one, "", tail );
- BinaryOperator* add2 =
- BinaryOperator::create( Instruction::Add, y, one, "", tail );
- BinaryOperator* div1 =
- BinaryOperator::create( Instruction::Div, add1, add2, "", tail);
- BinaryOperator* mult1 =
- BinaryOperator::create( Instruction::Mul, or1, div1, "", tail );
-
+ ConstantInt* one = ConstantInt::get(Type::IntTy, 1);
+ BinaryOperator* or1 = BinaryOperator::createOr(a, b, "", bb);
+ BinaryOperator* add1 = BinaryOperator::createAdd(x, one, "", bb);
+ BinaryOperator* add2 = BinaryOperator::createAdd(y, one, "", bb);
+ BinaryOperator* div1 = BinaryOperator::createDiv(add1, add2, "", bb);
+ BinaryOperator* mult1 = BinaryOperator::createMul(or1, div1, "", bb);
return mult1;
}
-</code></pre>
+</pre></div>
+
<p>"Okay, big deal," you say? It is a big deal. Here's why. Note that I didn't
have to tell this function which kinds of Values are being passed in. They could be
<code>Instruction</code>s, <code>Constant</code>s, <code>GlobalVariable</code>s, or
<li><em>Create your blocks early.</em> While writing your compiler, you
will encounter several situations where you know apriori that you will
need several blocks. For example, if-then-else, switch, while, and for
- statements in C/C++ all need multiple blocks for expression in LVVM.
+ statements in C/C++ all need multiple blocks for expression in LLVM.
The rule is, create them early.</li>
<li><em>Terminate your blocks early.</em> This just reduces the chances
that you forget to terminate your blocks which is required (go
before. This makes for some very clean compiler design.</li>
</ol>
<p>The foregoing is such an important principal, its worth making an idiom:</p>
-<pre><code>
-BasicBlock* bb = new BasicBlock();</li>
+<pre>
+BasicBlock* bb = new BasicBlock();
bb->getInstList().push_back( new Branch( ... ) );
new Instruction(..., bb->getTerminator() );
-</code></pre>
+</pre>
<p>To make this clear, consider the typical if-then-else statement
(see StackerCompiler::handle_if() method). We can set this up
in a single function using LLVM in the following way: </p>
<pre>
using namespace llvm;
BasicBlock*
-MyCompiler::handle_if( BasicBlock* bb, SetCondInst* condition )
+MyCompiler::handle_if( BasicBlock* bb, ICmpInst* condition )
{
// Create the blocks to contain code in the structure of if/then/else
BasicBlock* then_bb = new BasicBlock();
missed a few <em>very</em> key points:
</p>
<ul>
- <li>GetElementPtrInst gives you back a Value for the last thing indexed.</em>
- <li>All global variables in LLVM are <em>pointers</em>.
- <li>Pointers must also be dereferenced with the GetElementPtrInst instruction.
+<li>GetElementPtrInst gives you back a Value for the last thing indexed.</li>
+<li>All global variables in LLVM are <em>pointers</em>.</li>
+<li>Pointers must also be dereferenced with the GetElementPtrInst
+instruction.</li>
</ul>
<p>This means that when you look up an element in the global variable (assuming
it's a struct or array), you <em>must</em> deference the pointer first! For many
things, this leads to the idiom:
</p>
-<pre><code>
-std::vector<Value*> index_vector;
-index_vector.push_back( ConstantSInt::get( Type::LongTy, 0 );
+<pre>
+std::vector<Value*> index_vector;
+index_vector.push_back( ConstantInt::get( Type::LongTy, 0 );
// ... push other indices ...
GetElementPtrInst* gep = new GetElementPtrInst( ptr, index_vector );
-</code></pre>
+</pre>
<p>For example, suppose we have a global variable whose type is [24 x int]. The
variable itself represents a <em>pointer</em> to that array. To subscript the
array, we need two indices, not just one. The first index (0) dereferences the
carefully. Then, read it again.<p>
<p>Here are some handy tips that I discovered along the way:</p>
<ul>
- <li><em>Unitialized means external.</em> That is, the symbol is declared in the current
+ <li><em>Uninitialized means external.</em> That is, the symbol is declared in the current
module and can be used by that module, but it is not defined by that module.</li>
<li><em>Setting an initializer changes a global' linkage type.</em> Setting an
initializer changes a global's linkage type from whatever it was to a normal,
<ul>
<li>Constants are Values like anything else and can be operands of instructions</li>
<li>Integer constants, frequently needed, can be created using the static "get"
- methods of the ConstantInt, ConstantSInt, and ConstantUInt classes. The nice thing
- about these is that you can "get" any kind of integer quickly.</li>
- <li>There's a special method on Constant class which allows you to get the null
+ methods of the ConstantInt class. The nice thing about these is that you can
+ "get" any kind of integer quickly.</li>
+ <li>There's a special method on Constant class which allows you to get the null
constant for <em>any</em> type. This is really handy for initializing large
arrays or structures, etc.</li>
</ul>
linking.</p>
</div>
<!-- ======================================================================= -->
+<div class="doc_subsection"><a name="style"></a>Standard Style</div>
+<div class="doc_text">
+<p>TODO</p>
+</div>
+<!-- ======================================================================= -->
<div class="doc_subsection"><a name="builtins"></a>Built In Words</div>
<div class="doc_text">
<p>The built-in words of the Stacker language are put in several groups
</ol>
</div>
<div class="doc_text" >
- <table class="doc_table" style="border: 2px solid blue; border-collapse: collapse;" >
-<tr class="doc_table"><td colspan="4" style="border: 2px solid blue">Definition Of Operation Of Built In Words</td></tr>
-<tr class="doc_table"><td colspan="4" style="border: 2px solid blue"><b>LOGICAL OPERATIONS</b></td></tr>
-<tr class="doc_table">
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr class="doc_table"><td style="border: 2px solid blue"><</td>
- <td style="border: 2px solid blue">LT</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+ <table>
+<tr><th colspan="4">Definition Of Operation Of Built In Words</th></tr>
+<tr><th colspan="4"><b>LOGICAL OPERATIONS</b></th></tr>
+<tr>
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr>
+ <td><</td>
+ <td>LT</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is less than w2, TRUE is pushed back on
the stack, otherwise FALSE is pushed back on the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">></td>
- <td style="border: 2px solid blue">GT</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+<tr><td>></td>
+ <td>GT</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is greater than w2, TRUE is pushed back on
the stack, otherwise FALSE is pushed back on the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">>=</td>
- <td style="border: 2px solid blue">GE</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+<tr><td>>=</td>
+ <td>GE</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is greater than or equal to w2, TRUE is
pushed back on the stack, otherwise FALSE is pushed back
on the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue"><=</td>
- <td style="border: 2px solid blue">LE</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+<tr><td><=</td>
+ <td>LE</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is less than or equal to w2, TRUE is
pushed back on the stack, otherwise FALSE is pushed back
on the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">=</td>
- <td style="border: 2px solid blue">EQ</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+<tr><td>=</td>
+ <td>EQ</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is equal to w2, TRUE is
pushed back on the stack, otherwise FALSE is pushed back
</td>
</tr>
-<tr><td style="border: 2px solid blue"><></td>
- <td style="border: 2px solid blue">NE</td>
- <td style="border: 2px solid blue">w1 w2 -- b</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack and
+<tr><td><></td>
+ <td>NE</td>
+ <td>w1 w2 -- b</td>
+ <td>Two values (w1 and w2) are popped off the stack and
compared. If w1 is equal to w2, TRUE is
pushed back on the stack, otherwise FALSE is pushed back
</td>
</tr>
-<tr><td style="border: 2px solid blue">FALSE</td>
- <td style="border: 2px solid blue">FALSE</td>
- <td style="border: 2px solid blue"> -- b</td>
- <td style="border: 2px solid blue">The boolean value FALSE (0) is pushed on to the stack.</td>
+<tr><td>FALSE</td>
+ <td>FALSE</td>
+ <td> -- b</td>
+ <td>The boolean value FALSE (0) is pushed on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">TRUE</td>
- <td style="border: 2px solid blue">TRUE</td>
- <td style="border: 2px solid blue"> -- b</td>
- <td style="border: 2px solid blue">The boolean value TRUE (-1) is pushed on to the stack.</td>
+<tr><td>TRUE</td>
+ <td>TRUE</td>
+ <td> -- b</td>
+ <td>The boolean value TRUE (-1) is pushed on to the stack.</td>
</tr>
-<tr><td colspan="4"><b>BITWISE OPERATORS</b></td></tr>
+<tr><th colspan="4"><b>BITWISE OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue"><<</td>
- <td style="border: 2px solid blue">SHL</td>
- <td style="border: 2px solid blue">w1 w2 -- w1<<w2</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The w2
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td><<</td>
+ <td>SHL</td>
+ <td>w1 w2 -- w1<<w2</td>
+ <td>Two values (w1 and w2) are popped off the stack. The w2
operand is shifted left by the number of bits given by the
w1 operand. The result is pushed back to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">>></td>
- <td style="border: 2px solid blue">SHR</td>
- <td style="border: 2px solid blue">w1 w2 -- w1>>w2</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The w2
+<tr><td>>></td>
+ <td>SHR</td>
+ <td>w1 w2 -- w1>>w2</td>
+ <td>Two values (w1 and w2) are popped off the stack. The w2
operand is shifted right by the number of bits given by the
w1 operand. The result is pushed back to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">OR</td>
- <td style="border: 2px solid blue">OR</td>
- <td style="border: 2px solid blue">w1 w2 -- w2|w1</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+<tr><td>OR</td>
+ <td>OR</td>
+ <td>w1 w2 -- w2|w1</td>
+ <td>Two values (w1 and w2) are popped off the stack. The values
are bitwise OR'd together and pushed back on the stack. This is
not a logical OR. The sequence 1 2 OR yields 3 not 1.</td>
</tr>
-<tr><td style="border: 2px solid blue">AND</td>
- <td style="border: 2px solid blue">AND</td>
- <td style="border: 2px solid blue">w1 w2 -- w2&w1</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+<tr><td>AND</td>
+ <td>AND</td>
+ <td>w1 w2 -- w2&w1</td>
+ <td>Two values (w1 and w2) are popped off the stack. The values
are bitwise AND'd together and pushed back on the stack. This is
not a logical AND. The sequence 1 2 AND yields 0 not 1.</td>
</tr>
-<tr><td style="border: 2px solid blue">XOR</td>
- <td style="border: 2px solid blue">XOR</td>
- <td style="border: 2px solid blue">w1 w2 -- w2^w1</td>
- <td style="border: 2px solid blue">Two values (w1 and w2) are popped off the stack. The values
+<tr><td>XOR</td>
+ <td>XOR</td>
+ <td>w1 w2 -- w2^w1</td>
+ <td>Two values (w1 and w2) are popped off the stack. The values
are bitwise exclusive OR'd together and pushed back on the stack.
For example, The sequence 1 3 XOR yields 2.</td>
</tr>
-<tr><td colspan="4"><b>ARITHMETIC OPERATORS</b></td></tr>
+<tr><th colspan="4"><b>ARITHMETIC OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue">ABS</td>
- <td style="border: 2px solid blue">ABS</td>
- <td style="border: 2px solid blue">w -- |w|</td>
- <td style="border: 2px solid blue">One value s popped off the stack; its absolute value is computed
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td>ABS</td>
+ <td>ABS</td>
+ <td>w -- |w|</td>
+ <td>One value s popped off the stack; its absolute value is computed
and then pushed on to the stack. If w1 is -1 then w2 is 1. If w1 is
1 then w2 is also 1.</td>
</tr>
-<tr><td style="border: 2px solid blue">NEG</td>
- <td style="border: 2px solid blue">NEG</td>
- <td style="border: 2px solid blue">w -- -w</td>
- <td style="border: 2px solid blue">One value is popped off the stack which is negated and then
+<tr><td>NEG</td>
+ <td>NEG</td>
+ <td>w -- -w</td>
+ <td>One value is popped off the stack which is negated and then
pushed back on to the stack. If w1 is -1 then w2 is 1. If w1 is
1 then w2 is -1.</td>
</tr>
-<tr><td style="border: 2px solid blue"> + </td>
- <td style="border: 2px solid blue">ADD</td>
- <td style="border: 2px solid blue">w1 w2 -- w2+w1</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. Their sum is pushed back
+<tr><td> + </td>
+ <td>ADD</td>
+ <td>w1 w2 -- w2+w1</td>
+ <td>Two values are popped off the stack. Their sum is pushed back
on to the stack</td>
</tr>
-<tr><td style="border: 2px solid blue"> - </td>
- <td style="border: 2px solid blue">SUB</td>
- <td style="border: 2px solid blue">w1 w2 -- w2-w1</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. Their difference is pushed back
+<tr><td> - </td>
+ <td>SUB</td>
+ <td>w1 w2 -- w2-w1</td>
+ <td>Two values are popped off the stack. Their difference is pushed back
on to the stack</td>
</tr>
-<tr><td style="border: 2px solid blue"> * </td>
- <td style="border: 2px solid blue">MUL</td>
- <td style="border: 2px solid blue">w1 w2 -- w2*w1</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. Their product is pushed back
+<tr><td> * </td>
+ <td>MUL</td>
+ <td>w1 w2 -- w2*w1</td>
+ <td>Two values are popped off the stack. Their product is pushed back
on to the stack</td>
</tr>
-<tr><td style="border: 2px solid blue"> / </td>
- <td style="border: 2px solid blue">DIV</td>
- <td style="border: 2px solid blue">w1 w2 -- w2/w1</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. Their quotient is pushed back
+<tr><td> / </td>
+ <td>DIV</td>
+ <td>w1 w2 -- w2/w1</td>
+ <td>Two values are popped off the stack. Their quotient is pushed back
on to the stack</td>
</tr>
-<tr><td style="border: 2px solid blue">MOD</td>
- <td style="border: 2px solid blue">MOD</td>
- <td style="border: 2px solid blue">w1 w2 -- w2%w1</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. Their remainder after division
+<tr><td>MOD</td>
+ <td>MOD</td>
+ <td>w1 w2 -- w2%w1</td>
+ <td>Two values are popped off the stack. Their remainder after division
of w1 by w2 is pushed back on to the stack</td>
</tr>
-<tr><td style="border: 2px solid blue"> */ </td>
- <td style="border: 2px solid blue">STAR_SLAH</td>
- <td style="border: 2px solid blue">w1 w2 w3 -- (w3*w2)/w1</td>
- <td style="border: 2px solid blue">Three values are popped off the stack. The product of w1 and w2 is
+<tr><td> */ </td>
+ <td>STAR_SLAH</td>
+ <td>w1 w2 w3 -- (w3*w2)/w1</td>
+ <td>Three values are popped off the stack. The product of w1 and w2 is
divided by w3. The result is pushed back on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue"> ++ </td>
- <td style="border: 2px solid blue">INCR</td>
- <td style="border: 2px solid blue">w -- w+1</td>
- <td style="border: 2px solid blue">One value is popped off the stack. It is incremented by one and then
+<tr><td> ++ </td>
+ <td>INCR</td>
+ <td>w -- w+1</td>
+ <td>One value is popped off the stack. It is incremented by one and then
pushed back on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">DECR</td>
- <td style="border: 2px solid blue">w -- w-1</td>
- <td style="border: 2px solid blue">One value is popped off the stack. It is decremented by one and then
+<tr><td> -- </td>
+ <td>DECR</td>
+ <td>w -- w-1</td>
+ <td>One value is popped off the stack. It is decremented by one and then
pushed back on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">MIN</td>
- <td style="border: 2px solid blue">MIN</td>
- <td style="border: 2px solid blue">w1 w2 -- (w2<w1?w2:w1)</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. The larger one is pushed back
+<tr><td>MIN</td>
+ <td>MIN</td>
+ <td>w1 w2 -- (w2<w1?w2:w1)</td>
+ <td>Two values are popped off the stack. The larger one is pushed back
on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">MAX</td>
- <td style="border: 2px solid blue">MAX</td>
- <td style="border: 2px solid blue">w1 w2 -- (w2>w1?w2:w1)</td>
- <td style="border: 2px solid blue">Two values are popped off the stack. The larger value is pushed back
+<tr><td>MAX</td>
+ <td>MAX</td>
+ <td>w1 w2 -- (w2>w1?w2:w1)</td>
+ <td>Two values are popped off the stack. The larger value is pushed back
on to the stack.</td>
</tr>
-<tr><td colspan="4"><b>STACK MANIPULATION OPERATORS</b></td></tr>
+<tr><th colspan="4"><b>STACK MANIPULATION OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue">DROP</td>
- <td style="border: 2px solid blue">DROP</td>
- <td style="border: 2px solid blue">w -- </td>
- <td style="border: 2px solid blue">One value is popped off the stack.</td>
-</tr>
-<tr><td style="border: 2px solid blue">DROP2</td>
- <td style="border: 2px solid blue">DROP2</td>
- <td style="border: 2px solid blue">w1 w2 -- </td>
- <td style="border: 2px solid blue">Two values are popped off the stack.</td>
-</tr>
-<tr><td style="border: 2px solid blue">NIP</td>
- <td style="border: 2px solid blue">NIP</td>
- <td style="border: 2px solid blue">w1 w2 -- w2</td>
- <td style="border: 2px solid blue">The second value on the stack is removed from the stack. That is,
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td>DROP</td>
+ <td>DROP</td>
+ <td>w -- </td>
+ <td>One value is popped off the stack.</td>
+</tr>
+<tr><td>DROP2</td>
+ <td>DROP2</td>
+ <td>w1 w2 -- </td>
+ <td>Two values are popped off the stack.</td>
+</tr>
+<tr><td>NIP</td>
+ <td>NIP</td>
+ <td>w1 w2 -- w2</td>
+ <td>The second value on the stack is removed from the stack. That is,
a value is popped off the stack and retained. Then a second value is
popped and the retained value is pushed.</td>
</tr>
-<tr><td style="border: 2px solid blue">NIP2</td>
- <td style="border: 2px solid blue">NIP2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4</td>
- <td style="border: 2px solid blue">The third and fourth values on the stack are removed from it. That is,
+<tr><td>NIP2</td>
+ <td>NIP2</td>
+ <td>w1 w2 w3 w4 -- w3 w4</td>
+ <td>The third and fourth values on the stack are removed from it. That is,
two values are popped and retained. Then two more values are popped and
the two retained values are pushed back on.</td>
</tr>
-<tr><td style="border: 2px solid blue">DUP</td>
- <td style="border: 2px solid blue">DUP</td>
- <td style="border: 2px solid blue">w1 -- w1 w1</td>
- <td style="border: 2px solid blue">One value is popped off the stack. That value is then pushed on to
+<tr><td>DUP</td>
+ <td>DUP</td>
+ <td>w1 -- w1 w1</td>
+ <td>One value is popped off the stack. That value is then pushed on to
the stack twice to duplicate the top stack vaue.</td>
</tr>
-<tr><td style="border: 2px solid blue">DUP2</td>
- <td style="border: 2px solid blue">DUP2</td>
- <td style="border: 2px solid blue">w1 w2 -- w1 w2 w1 w2</td>
- <td style="border: 2px solid blue">The top two values on the stack are duplicated. That is, two vaues
+<tr><td>DUP2</td>
+ <td>DUP2</td>
+ <td>w1 w2 -- w1 w2 w1 w2</td>
+ <td>The top two values on the stack are duplicated. That is, two vaues
are popped off the stack. They are alternately pushed back on the
stack twice each.</td>
</tr>
-<tr><td style="border: 2px solid blue">SWAP</td>
- <td style="border: 2px solid blue">SWAP</td>
- <td style="border: 2px solid blue">w1 w2 -- w2 w1</td>
- <td style="border: 2px solid blue">The top two stack items are reversed in their order. That is, two
+<tr><td>SWAP</td>
+ <td>SWAP</td>
+ <td>w1 w2 -- w2 w1</td>
+ <td>The top two stack items are reversed in their order. That is, two
values are popped off the stack and pushed back on to the stack in
the opposite order they were popped.</td>
</tr>
-<tr><td style="border: 2px solid blue">SWAP2</td>
- <td style="border: 2px solid blue">SWAP2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4 w2 w1</td>
- <td style="border: 2px solid blue">The top four stack items are swapped in pairs. That is, two values
+<tr><td>SWAP2</td>
+ <td>SWAP2</td>
+ <td>w1 w2 w3 w4 -- w3 w4 w2 w1</td>
+ <td>The top four stack items are swapped in pairs. That is, two values
are popped and retained. Then, two more values are popped and retained.
The values are pushed back on to the stack in the reverse order but
- in pairs.</p>
+ in pairs.</td>
</tr>
-<tr><td style="border: 2px solid blue">OVER</td>
- <td style="border: 2px solid blue">OVER</td>
- <td style="border: 2px solid blue">w1 w2-- w1 w2 w1</td>
- <td style="border: 2px solid blue">Two values are popped from the stack. They are pushed back
+<tr><td>OVER</td>
+ <td>OVER</td>
+ <td>w1 w2-- w1 w2 w1</td>
+ <td>Two values are popped from the stack. They are pushed back
on to the stack in the order w1 w2 w1. This seems to cause the
top stack element to be duplicated "over" the next value.</td>
</tr>
-<tr><td style="border: 2px solid blue">OVER2</td>
- <td style="border: 2px solid blue">OVER2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 -- w1 w2 w3 w4 w1 w2</td>
- <td style="border: 2px solid blue">The third and fourth values on the stack are replicated on to the
+<tr><td>OVER2</td>
+ <td>OVER2</td>
+ <td>w1 w2 w3 w4 -- w1 w2 w3 w4 w1 w2</td>
+ <td>The third and fourth values on the stack are replicated on to the
top of the stack</td>
</tr>
-<tr><td style="border: 2px solid blue">ROT</td>
- <td style="border: 2px solid blue">ROT</td>
- <td style="border: 2px solid blue">w1 w2 w3 -- w2 w3 w1</td>
- <td style="border: 2px solid blue">The top three values are rotated. That is, three value are popped
+<tr><td>ROT</td>
+ <td>ROT</td>
+ <td>w1 w2 w3 -- w2 w3 w1</td>
+ <td>The top three values are rotated. That is, three value are popped
off the stack. They are pushed back on to the stack in the order
w1 w3 w2.</td>
</tr>
-<tr><td style="border: 2px solid blue">ROT2</td>
- <td style="border: 2px solid blue">ROT2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
- <td style="border: 2px solid blue">Like ROT but the rotation is done using three pairs instead of
+<tr><td>ROT2</td>
+ <td>ROT2</td>
+ <td>w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
+ <td>Like ROT but the rotation is done using three pairs instead of
three singles.</td>
</tr>
-<tr><td style="border: 2px solid blue">RROT</td>
- <td style="border: 2px solid blue">RROT</td>
- <td style="border: 2px solid blue">w1 w2 w3 -- w2 w3 w1</td>
- <td style="border: 2px solid blue">Reverse rotation. Like ROT, but it rotates the other way around.
+<tr><td>RROT</td>
+ <td>RROT</td>
+ <td>w1 w2 w3 -- w3 w1 w2</td>
+ <td>Reverse rotation. Like ROT, but it rotates the other way around.
Essentially, the third element on the stack is moved to the top
of the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">RROT2</td>
- <td style="border: 2px solid blue">RROT2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
- <td style="border: 2px solid blue">Double reverse rotation. Like RROT but the rotation is done using
+<tr><td>RROT2</td>
+ <td>RROT2</td>
+ <td>w1 w2 w3 w4 w5 w6 -- w3 w4 w5 w6 w1 w2</td>
+ <td>Double reverse rotation. Like RROT but the rotation is done using
three pairs instead of three singles. The fifth and sixth stack
elements are moved to the first and second positions</td>
</tr>
-<tr><td style="border: 2px solid blue">TUCK</td>
- <td style="border: 2px solid blue">TUCK</td>
- <td style="border: 2px solid blue">w1 w2 -- w2 w1 w2</td>
- <td style="border: 2px solid blue">Similar to OVER except that the second operand is being
+<tr><td>TUCK</td>
+ <td>TUCK</td>
+ <td>w1 w2 -- w2 w1 w2</td>
+ <td>Similar to OVER except that the second operand is being
replicated. Essentially, the first operand is being "tucked"
in between two instances of the second operand. Logically, two
values are popped off the stack. They are placed back on the
stack in the order w2 w1 w2.</td>
</tr>
-<tr><td style="border: 2px solid blue">TUCK2</td>
- <td style="border: 2px solid blue">TUCK2</td>
- <td style="border: 2px solid blue">w1 w2 w3 w4 -- w3 w4 w1 w2 w3 w4</td>
- <td style="border: 2px solid blue">Like TUCK but a pair of elements is tucked over two pairs.
+<tr><td>TUCK2</td>
+ <td>TUCK2</td>
+ <td>w1 w2 w3 w4 -- w3 w4 w1 w2 w3 w4</td>
+ <td>Like TUCK but a pair of elements is tucked over two pairs.
That is, the top two elements of the stack are duplicated and
inserted into the stack at the fifth and positions.</td>
</tr>
-<tr><td style="border: 2px solid blue">PICK</td>
- <td style="border: 2px solid blue">PICK</td>
- <td style="border: 2px solid blue">x0 ... Xn n -- x0 ... Xn x0</td>
- <td style="border: 2px solid blue">The top of the stack is used as an index into the remainder of
+<tr><td>PICK</td>
+ <td>PICK</td>
+ <td>x0 ... Xn n -- x0 ... Xn x0</td>
+ <td>The top of the stack is used as an index into the remainder of
the stack. The element at the nth position replaces the index
(top of stack). This is useful for cycling through a set of
values. Note that indexing is zero based. So, if n=0 then you
get the second item on the stack. If n=1 you get the third, etc.
Note also that the index is replaced by the n'th value. </td>
</tr>
-<tr><td style="border: 2px solid blue">SELECT</td>
- <td style="border: 2px solid blue">SELECT</td>
- <td style="border: 2px solid blue">m n X0..Xm Xm+1 .. Xn -- Xm</td>
- <td style="border: 2px solid blue">This is like PICK but the list is removed and you need to specify
+<tr><td>SELECT</td>
+ <td>SELECT</td>
+ <td>m n X0..Xm Xm+1 .. Xn -- Xm</td>
+ <td>This is like PICK but the list is removed and you need to specify
both the index and the size of the list. Careful with this one,
the wrong value for n can blow away a huge amount of the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">ROLL</td>
- <td style="border: 2px solid blue">ROLL</td>
- <td style="border: 2px solid blue">x0 x1 .. xn n -- x1 .. xn x0</td>
- <td style="border: 2px solid blue"><b>Not Implemented</b>. This one has been left as an exercise to
+<tr><td>ROLL</td>
+ <td>ROLL</td>
+ <td>x0 x1 .. xn n -- x1 .. xn x0</td>
+ <td><b>Not Implemented</b>. This one has been left as an exercise to
the student. See <a href="#exercise">Exercise</a>. ROLL requires
a value, "n", to be on the top of the stack. This value specifies how
far into the stack to "roll". The n'th value is <em>moved</em> (not
how much to rotate. That is, ROLL with n=1 is the same as ROT and
ROLL with n=2 is the same as ROT2.</td>
</tr>
-<tr><td colspan="4"><b>MEMORY OPERATORS</b></td></tr>
+<tr><th colspan="4"><b>MEMORY OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue">MALLOC</td>
- <td style="border: 2px solid blue">MALLOC</td>
- <td style="border: 2px solid blue">w1 -- p</td>
- <td style="border: 2px solid blue">One value is popped off the stack. The value is used as the size
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td>MALLOC</td>
+ <td>MALLOC</td>
+ <td>w1 -- p</td>
+ <td>One value is popped off the stack. The value is used as the size
of a memory block to allocate. The size is in bytes, not words.
The memory allocation is completed and the address of the memory
block is pushed on to the stack.</td>
</tr>
-<tr><td style="border: 2px solid blue">FREE</td>
- <td style="border: 2px solid blue">FREE</td>
- <td style="border: 2px solid blue">p -- </td>
- <td style="border: 2px solid blue">One pointer value is popped off the stack. The value should be
+<tr><td>FREE</td>
+ <td>FREE</td>
+ <td>p -- </td>
+ <td>One pointer value is popped off the stack. The value should be
the address of a memory block created by the MALLOC operation. The
associated memory block is freed. Nothing is pushed back on the
stack. Many bugs can be created by attempting to FREE something
the stack (for the FREE at the end) and that every use of the
pointer is preceded by a DUP to retain the copy for FREE.</td>
</tr>
-<tr><td style="border: 2px solid blue">GET</td>
- <td style="border: 2px solid blue">GET</td>
- <td style="border: 2px solid blue">w1 p -- w2 p</td>
- <td style="border: 2px solid blue">An integer index and a pointer to a memory block are popped of
+<tr><td>GET</td>
+ <td>GET</td>
+ <td>w1 p -- w2 p</td>
+ <td>An integer index and a pointer to a memory block are popped of
the block. The index is used to index one byte from the memory
block. That byte value is retained, the pointer is pushed again
and the retained value is pushed. Note that the pointer value
s essentially retained in its position so this doesn't count
as a "use ptr" in the FREE idiom.</td>
</tr>
-<tr><td style="border: 2px solid blue">PUT</td>
- <td style="border: 2px solid blue">PUT</td>
- <td style="border: 2px solid blue">w1 w2 p -- p </td>
- <td style="border: 2px solid blue">An integer value is popped of the stack. This is the value to
+<tr><td>PUT</td>
+ <td>PUT</td>
+ <td>w1 w2 p -- p </td>
+ <td>An integer value is popped of the stack. This is the value to
be put into a memory block. Another integer value is popped of
the stack. This is the indexed byte in the memory block. A
pointer to the memory block is popped off the stack. The
pushed back on the stack so this doesn't count as a "use ptr"
in the FREE idiom.</td>
</tr>
-<tr><td colspan="4"><b>CONTROL FLOW OPERATORS</b></td></tr>
+<tr><th colspan="4"><b>CONTROL FLOW OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue">RETURN</td>
- <td style="border: 2px solid blue">RETURN</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">The currently executing definition returns immediately to its caller.
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td>RETURN</td>
+ <td>RETURN</td>
+ <td> -- </td>
+ <td>The currently executing definition returns immediately to its caller.
Note that there is an implicit <code>RETURN</code> at the end of each
definition, logically located at the semi-colon. The sequence
<code>RETURN ;</code> is valid but redundant.</td>
</tr>
-<tr><td style="border: 2px solid blue">EXIT</td>
- <td style="border: 2px solid blue">EXIT</td>
- <td style="border: 2px solid blue">w1 -- </td>
- <td style="border: 2px solid blue">A return value for the program is popped off the stack. The program is
+<tr><td>EXIT</td>
+ <td>EXIT</td>
+ <td>w1 -- </td>
+ <td>A return value for the program is popped off the stack. The program is
then immediately terminated. This is normally an abnormal exit from the
program. For a normal exit (when <code>MAIN</code> finishes), the exit
code will always be zero in accordance with UNIX conventions.</td>
</tr>
-<tr><td style="border: 2px solid blue">RECURSE</td>
- <td style="border: 2px solid blue">RECURSE</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">The currently executed definition is called again. This operation is
+<tr><td>RECURSE</td>
+ <td>RECURSE</td>
+ <td> -- </td>
+ <td>The currently executed definition is called again. This operation is
needed since the definition of a word doesn't exist until the semi colon
is reacher. Attempting something like:<br/>
<code> : recurser recurser ; </code><br/> will yield and error saying that
to:<br/>
<code> : recurser RECURSE ; </code></td>
</tr>
-<tr><td style="border: 2px solid blue">IF (words...) ENDIF</td>
- <td style="border: 2px solid blue">IF (words...) ENDIF</td>
- <td style="border: 2px solid blue">b -- </td>
- <td style="border: 2px solid blue">A boolean value is popped of the stack. If it is non-zero then the "words..."
+<tr><td>IF (words...) ENDIF</td>
+ <td>IF (words...) ENDIF</td>
+ <td>b -- </td>
+ <td>A boolean value is popped of the stack. If it is non-zero then the "words..."
are executed. Otherwise, execution continues immediately following the ENDIF.</td>
</tr>
-<tr><td style="border: 2px solid blue">IF (words...) ELSE (words...) ENDIF</td>
- <td style="border: 2px solid blue">IF (words...) ELSE (words...) ENDIF</td>
- <td style="border: 2px solid blue">b -- </td>
- <td style="border: 2px solid blue">A boolean value is popped of the stack. If it is non-zero then the "words..."
+<tr><td>IF (words...) ELSE (words...) ENDIF</td>
+ <td>IF (words...) ELSE (words...) ENDIF</td>
+ <td>b -- </td>
+ <td>A boolean value is popped of the stack. If it is non-zero then the "words..."
between IF and ELSE are executed. Otherwise the words between ELSE and ENDIF are
executed. In either case, after the (words....) have executed, execution continues
immediately following the ENDIF. </td>
</tr>
-<tr><td style="border: 2px solid blue">WHILE (words...) END</td>
- <td style="border: 2px solid blue">WHILE (words...) END</td>
- <td style="border: 2px solid blue">b -- b </td>
- <td style="border: 2px solid blue">The boolean value on the top of the stack is examined. If it is non-zero then the
- "words..." between WHILE and END are executed. Execution then begins again at the WHILE where another
- boolean is popped off the stack. To prevent this operation from eating up the entire
- stack, you should push on to the stack (just before the END) a boolean value that indicates
- whether to terminate. Note that since booleans and integers can be coerced you can
- use the following "for loop" idiom:<br/>
- <code>(push count) WHILE (words...) -- END</code><br/>
+<tr><td>WHILE word END</td>
+ <td>WHILE word END</td>
+ <td>b -- b </td>
+ <td>The boolean value on the top of the stack is examined (not popped). If
+ it is non-zero then the "word" between WHILE and END is executed.
+ Execution then begins again at the WHILE where the boolean on the top of
+ the stack is examined again. The stack is not modified by the WHILE...END
+ loop, only examined. It is imperative that the "word" in the body of the
+ loop ensure that the top of the stack contains the next boolean to examine
+ when it completes. Note that since booleans and integers can be coerced
+ you can use the following "for loop" idiom:<br/>
+ <code>(push count) WHILE word -- END</code><br/>
For example:<br/>
- <code>10 WHILE DUP >d -- END</code><br/>
- This will print the numbers from 10 down to 1. 10 is pushed on the stack. Since that is
- non-zero, the while loop is entered. The top of the stack (10) is duplicated and then
- printed out with >d. The top of the stack is decremented, yielding 9 and control is
- transfered back to the WHILE keyword. The process starts all over again and repeats until
- the top of stack is decremented to 0 at which the WHILE test fails and control is
- transfered to the word after the END.</td>
-</tr>
-<tr><td colspan="4"><b>INPUT & OUTPUT OPERATORS</b></td></tr>
+ <code>10 WHILE >d -- END</code><br/>
+ This will print the numbers from 10 down to 1. 10 is pushed on the
+ stack. Since that is non-zero, the while loop is entered. The top of
+ the stack (10) is printed out with >d. The top of the stack is
+ decremented, yielding 9 and control is transfered back to the WHILE
+ keyword. The process starts all over again and repeats until
+ the top of stack is decremented to 0 at which point the WHILE test
+ fails and control is transfered to the word after the END.
+ </td>
+</tr>
+<tr><th colspan="4"><b>INPUT & OUTPUT OPERATORS</b></th></tr>
<tr>
- <td style="border: 2px solid blue"><u>Word</u></td>
- <td style="border: 2px solid blue"><u>Name</u></td>
- <td style="border: 2px solid blue"><u>Operation</u></td>
- <td style="border: 2px solid blue"><u>Description</u></td>
-</tr>
-<tr><td style="border: 2px solid blue">SPACE</td>
- <td style="border: 2px solid blue">SPACE</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A space character is put out. There is no stack effect.</td>
-</tr>
-<tr><td style="border: 2px solid blue">TAB</td>
- <td style="border: 2px solid blue">TAB</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A tab character is put out. There is no stack effect.</td>
-</tr>
-<tr><td style="border: 2px solid blue">CR</td>
- <td style="border: 2px solid blue">CR</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A carriage return character is put out. There is no stack effect.</td>
-</tr>
-<tr><td style="border: 2px solid blue">>s</td>
- <td style="border: 2px solid blue">OUT_STR</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A string pointer is popped from the stack. It is put out.</td>
-</tr>
-<tr><td style="border: 2px solid blue">>d</td>
- <td style="border: 2px solid blue">OUT_STR</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A value is popped from the stack. It is put out as a decimal integer.</td>
-</tr>
-<tr><td style="border: 2px solid blue">>c</td>
- <td style="border: 2px solid blue">OUT_CHR</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">A value is popped from the stack. It is put out as an ASCII character.</td>
-</tr>
-<tr><td style="border: 2px solid blue"><s</td>
- <td style="border: 2px solid blue">IN_STR</td>
- <td style="border: 2px solid blue"> -- s </td>
- <td style="border: 2px solid blue">A string is read from the input via the scanf(3) format string " %as". The
- resulting string is pushed on to the stack.</td>
-</tr>
-<tr><td style="border: 2px solid blue"><d</td>
- <td style="border: 2px solid blue">IN_STR</td>
- <td style="border: 2px solid blue"> -- w </td>
- <td style="border: 2px solid blue">An integer is read from the input via the scanf(3) format string " %d". The
- resulting value is pushed on to the stack</td>
-</tr>
-<tr><td style="border: 2px solid blue"><c</td>
- <td style="border: 2px solid blue">IN_CHR</td>
- <td style="border: 2px solid blue"> -- w </td>
- <td style="border: 2px solid blue">A single character is read from the input via the scanf(3) format string
- " %c". The value is converted to an integer and pushed on to the stack.</td>
-</tr>
-<tr><td style="border: 2px solid blue">DUMP</td>
- <td style="border: 2px solid blue">DUMP</td>
- <td style="border: 2px solid blue"> -- </td>
- <td style="border: 2px solid blue">The stack contents are dumped to standard output. This is useful for
+ <td>Word</td>
+ <td>Name</td>
+ <td>Operation</td>
+ <td>Description</td>
+</tr>
+<tr><td>SPACE</td>
+ <td>SPACE</td>
+ <td> -- </td>
+ <td>A space character is put out. There is no stack effect.</td>
+</tr>
+<tr><td>TAB</td>
+ <td>TAB</td>
+ <td> -- </td>
+ <td>A tab character is put out. There is no stack effect.</td>
+</tr>
+<tr><td>CR</td>
+ <td>CR</td>
+ <td> -- </td>
+ <td>A carriage return character is put out. There is no stack effect.</td>
+</tr>
+<tr><td>>s</td>
+ <td>OUT_STR</td>
+ <td> -- </td>
+ <td>A string pointer is popped from the stack. It is put out.</td>
+</tr>
+<tr><td>>d</td>
+ <td>OUT_STR</td>
+ <td> -- </td>
+ <td>A value is popped from the stack. It is put out as a decimal
+ integer.</td>
+</tr>
+<tr><td>>c</td>
+ <td>OUT_CHR</td>
+ <td> -- </td>
+ <td>A value is popped from the stack. It is put out as an ASCII
+ character.</td>
+</tr>
+<tr><td><s</td>
+ <td>IN_STR</td>
+ <td> -- s </td>
+ <td>A string is read from the input via the scanf(3) format string " %as".
+ The resulting string is pushed on to the stack.</td>
+</tr>
+<tr><td><d</td>
+ <td>IN_STR</td>
+ <td> -- w </td>
+ <td>An integer is read from the input via the scanf(3) format string " %d".
+ The resulting value is pushed on to the stack</td>
+</tr>
+<tr><td><c</td>
+ <td>IN_CHR</td>
+ <td> -- w </td>
+ <td>A single character is read from the input via the scanf(3) format string
+ " %c". The value is converted to an integer and pushed on to the stack.</td>
+</tr>
+<tr><td>DUMP</td>
+ <td>DUMP</td>
+ <td> -- </td>
+ <td>The stack contents are dumped to standard output. This is useful for
debugging your definitions. Put DUMP at the beginning and end of a definition
to see instantly the net effect of the definition.</td>
</tr>
</table>
+
</div>
<!-- ======================================================================= -->
<div class="doc_section"> <a name="example">Prime: A Complete Example</a></div>
################################################################################
# Utility definitions
################################################################################
-: print >d CR ;
+: print >d CR ;
: it_is_a_prime TRUE ;
: it_is_not_a_prime FALSE ;
: continue_loop TRUE ;
# This definition tries an actual division of a candidate prime number. It
# determines whether the division loop on this candidate should continue or
# not.
-# STACK<:
+# STACK<:
# div - the divisor to try
# p - the prime number we are working on
-# STACK>:
+# STACK>:
# cont - should we continue the loop ?
# div - the next divisor to try
# p - the prime number we are working on
# cont - should we continue the loop (ignored)?
# div - the divisor to try
# p - the prime number we are working on
-# STACK>:
+# STACK>:
# cont - should we continue the loop ?
# div - the next divisor to try
# p - the prime number we are working on
# definition which returns a loop continuation value (which we also seed with
# the value 1). After the loop, we check the divisor. If it decremented all
# the way to zero then we found a prime, otherwise we did not find one.
-# STACK<:
+# STACK<:
# p - the prime number to check
-# STACK>:
+# STACK>:
# yn - boolean indicating if its a prime or not
# p - the prime number checked
################################################################################
################################################################################
# This definition determines if the number on the top of the stack is a prime
-# or not. It does this by testing if the value is degenerate (<= 3) and
+# or not. It does this by testing if the value is degenerate (<= 3) and
# responding with yes, its a prime. Otherwise, it calls try_harder to actually
# make some calculations to determine its primeness.
-# STACK<:
+# STACK<:
# p - the prime number to check
-# STACK>:
+# STACK>:
# yn - boolean indicating if its a prime or not
# p - the prime number checked
################################################################################
: is_prime
DUP ( save the prime number )
- 3 >= IF ( see if its <= 3 )
+ 3 >= IF ( see if its <= 3 )
it_is_a_prime ( its <= 3 just indicate its prime )
ELSE
try_harder ( have to do a little more work )
################################################################################
# This definition is called when it is time to exit the program, after we have
# found a sufficiently large number of primes.
-# STACK<: ignored
-# STACK>: exits
+# STACK<: ignored
+# STACK>: exits
################################################################################
: done
- "Finished" >s CR ( say we are finished )
+ "Finished" >s CR ( say we are finished )
0 EXIT ( exit nicely )
;
# If it is a prime, it prints it. Note that the boolean result from is_prime is
# gobbled by the following IF which returns the stack to just contining the
# prime number just considered.
-# STACK<:
+# STACK<:
# p - one less than the prime number to consider
-# STACK>
+# STAC>K
# p+1 - the prime number considered
################################################################################
: consider_prime
DUP ( save the prime number to consider )
- 1000000 < IF ( check to see if we are done yet )
+ 1000000 < IF ( check to see if we are done yet )
done ( we are done, call "done" )
ENDIF
++ ( increment to next prime number )
# This definition starts at one, prints it out and continues into a loop calling
# consider_prime on each iteration. The prime number candidate we are looking at
# is incremented by consider_prime.
-# STACK<: empty
-# STACK>: empty
+# STACK<: empty
+# STACK>: empty
################################################################################
: find_primes
- "Prime Numbers: " >s CR ( say hello )
+ "Prime Numbers: " >s CR ( say hello )
DROP ( get rid of that pesky string )
1 ( stoke the fires )
print ( print the first one, we know its prime )
#
################################################################################
: say_yes
- >d ( Print the prime number )
+ >d ( Print the prime number )
" is prime." ( push string to output )
- >s ( output it )
+ >s ( output it )
CR ( print carriage return )
DROP ( pop string )
;
: say_no
- >d ( Print the prime number )
+ >d ( Print the prime number )
" is NOT prime." ( push string to put out )
- >s ( put out the string )
+ >s ( put out the string )
CR ( print carriage return )
DROP ( pop string )
;
################################################################################
# This definition processes a single command line argument and determines if it
# is a prime number or not.
-# STACK<:
+# STACK<:
# n - number of arguments
# arg1 - the prime numbers to examine
-# STACK>:
+# STACK>:
# n-1 - one less than number of arguments
# arg2 - we processed one argument
################################################################################
################################################################################
# The MAIN program just prints a banner and processes its arguments.
-# STACK<:
+# STACK<:
# n - number of arguments
# ... - the arguments
################################################################################
################################################################################
# The MAIN program just prints a banner and processes its arguments.
-# STACK<: arguments
+# STACK<: arguments
################################################################################
: MAIN
NIP ( get rid of the program name )
-- ( reduce number of arguments )
DUP ( save the arg counter )
- 1 <= IF ( See if we got an argument )
+ 1 <= IF ( See if we got an argument )
process_arguments ( tell user if they are prime )
ELSE
find_primes ( see how many we can find )
<div class="doc_subsection"> <a name="directory">Directory Structure</a></div>
<div class="doc_text">
<p>The source code, test programs, and sample programs can all be found
-under the LLVM "projects" directory. You will need to obtain the LLVM sources
-to find it (either via anonymous CVS or a tarball. See the
-<a href="GettingStarted.html">Getting Started</a> document).</p>
-<p>Under the "projects" directory there is a directory named "Stacker". That
-directory contains everything, as follows:</p>
+in the LLVM repository named <tt>llvm-stacker</tt> This should be checked out to
+the <tt>projects</tt> directory so that it will auto-configure. To do that, make
+sure you have the llvm sources in <tt><i>llvm</i></tt>
+(see <a href="GettingStarted.html">Getting Started</a>) and then use these
+commands:<pre>
+ cd <i>llvm</i>/projects
+ cvs co llvm-stacker</pre>
+</p>
+<p>Under the <tt>projects/llvm-stacker</tt> directory you will find the
+implementation of the Stacker compiler, as follows:</p>
<ul>
<li><em>lib</em> - contains most of the source code
<ul>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="lexer"></a>The Lexer</div>
<div class="doc_text">
-<p>See projects/Stacker/lib/compiler/Lexer.l</p>
-</p></div>
+<p>See projects/llvm-stacker/lib/compiler/Lexer.l</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="parser"></a>The Parser</div>
<div class="doc_text">
-<p>See projects/Stacker/lib/compiler/StackerParser.y</p>
-</p></div>
+<p>See projects/llvm-stacker/lib/compiler/StackerParser.y</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="compiler"></a>The Compiler</div>
<div class="doc_text">
-<p>See projects/Stacker/lib/compiler/StackerCompiler.cpp</p>
-</p></div>
+<p>See projects/llvm-stacker/lib/compiler/StackerCompiler.cpp</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="runtime"></a>The Runtime</div>
<div class="doc_text">
-<p>See projects/Stacker/lib/runtime/stacker_rt.c</p>
-</p></div>
+<p>See projects/llvm-stacker/lib/runtime/stacker_rt.c</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="driver"></a>Compiler Driver</div>
<div class="doc_text">
-<p>See projects/Stacker/tools/stkrc/stkrc.cpp</p>
-</p></div>
+<p>See projects/llvm-stacker/tools/stkrc/stkrc.cpp</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"><a name="tests"></a>Test Programs</div>
<div class="doc_text">
-<p>See projects/Stacker/test/*.st</p>
-</p></div>
+<p>See projects/llvm-stacker/test/*.st</p>
+</div>
<!-- ======================================================================= -->
<div class="doc_subsection"> <a name="exercise">Exercise</a></div>
<div class="doc_text">
by the compiler. That means you don't have to futz around with figuring out how
to get the keyword recognized. It already is. The part of the compiler that
you need to implement is the <code>ROLL</code> case in the
-<code>StackerCompiler::handle_word(int)</code> method.</p> See the implementations
-of PICk and SELECT in the same method to get some hints about how to complete
-this exercise.<p>
+<code>StackerCompiler::handle_word(int)</code> method.</p> See the
+implementations of PICK and SELECT in the same method to get some hints about
+
how to complete this exercise.<p>
<p>Good luck!</p>
</div>
<!-- ======================================================================= -->
-<div class="doc_subsection">
<a name="todo">Things Remaining To Be Done</a></div>
+<div class="doc_subsection"><a name="todo">Things Remaining To Be Done</a></div>
<div class="doc_text">
<p>The initial implementation of Stacker has several deficiencies. If you're
interested, here are some things that could be implemented better:</p>
<li>Write an LLVM pass to compute the correct stack depth needed by the
program. Currently the stack is set to a fixed number which means programs
with large numbers of definitions might fail.</li>
- <li>Enhance to run on 64-bit platforms like SPARC. Right now the size of a
- pointer on 64-bit machines will cause incorrect results because of the 32-bit
- size of a stack element currently supported. This feature was not implemented
- because LLVM needs a union type to be able to support the different sizes
- correctly (portably and efficiently).</li>
<li>Write an LLVM pass to optimize the use of the global stack. The code
emitted currently is somewhat wasteful. It gets cleaned up a lot by existing
passes but more could be done.</li>
- <li>Add -O -O1 -O2 and -O3 optimization switches to the compiler driver to
- allow LLVM optimization without using "opt."</li>
- <li>Make the compiler driver use the LLVM linking facilities (with IPO) before
- depending on GCC to do the final link.</li>
+ <li>Make the compiler driver use the LLVM linking facilities (with IPO)
+ before depending on GCC to do the final link.</li>
<li>Clean up parsing. It doesn't handle errors very well.</li>
<li>Rearrange the StackerCompiler.cpp code to make better use of inserting
instructions before a block's terminating instruction. I didn't figure this
- technique out until I was nearly done with LLVM. As it is, its a bad example
+ technique out until I was nearly done with LLVM. As it is, its a bad example
of how to insert instructions!</li>
<li>Provide for I/O to arbitrary files instead of just stdin/stdout.</li>
<li>Write additional built-in words; with inspiration from FORTH</li>
<a href="#lessons">Lessons I Learned About LLVM</a> section.</li>
</ol>
</div>
-<!-- ======================================================================= -->
+
+<!-- *********************************************************************** -->
+
<hr>
-<div class="doc_footer">
-<address><a href="mailto:rspencer@x10sys.com">Reid Spencer</a></address>
-<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
-<br>Last modified: $Date$ </div>
+<address>
+ <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
+ src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
+ <a href="http://validator.w3.org/check/referer"><img
+ src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
+
+ <a href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
+ <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
+ Last modified: $Date$
+</address>
+
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