for <tt>RegisterClass</tt>, the last parameter of which is a list of
registers. Just commenting some out is one simple way to avoid them being
used. A more polite way is to explicitly exclude some registers from
- the <i>allocation order</i>. See the definition of the <tt>GR</tt> register
- class in <tt>lib/Target/IA64/IA64RegisterInfo.td</tt> for an example of this
- (e.g., <tt>numReservedRegs</tt> registers are hidden.)</p>
+ the <i>allocation order</i>. See the definition of the <tt>GR8</tt> register
+ class in <tt>lib/Target/X86/X86RegisterInfo.td</tt> for an example of this.
+ </p>
<p>Virtual registers are also denoted by integer numbers. Contrary to physical
registers, different virtual registers never share the same number. The
<div class="doc_code">
<pre>
-$ llc -f -regalloc=simple file.bc -o sp.s;
-$ llc -f -regalloc=local file.bc -o lc.s;
-$ llc -f -regalloc=linearscan file.bc -o ln.s;
+$ llc -regalloc=simple file.bc -o sp.s;
+$ llc -regalloc=local file.bc -o lc.s;
+$ llc -regalloc=linearscan file.bc -o ln.s;
</pre>
</div>
<div class="doc_code">
<pre>
-Base + [1,2,4,8] * IndexReg + Disp32
+SegmentReg: Base + [1,2,4,8] * IndexReg + Disp32
</pre>
</div>
-<p>In order to represent this, LLVM tracks no less than 4 operands for each
+<p>In order to represent this, LLVM tracks no less than 5 operands for each
memory operand of this form. This means that the "load" form of
'<tt>mov</tt>' has the following <tt>MachineOperand</tt>s in this order:</p>
<div class="doc_code">
<pre>
-Index: 0 | 1 2 3 4
-Meaning: DestReg, | BaseReg, Scale, IndexReg, Displacement
-OperandTy: VirtReg, | VirtReg, UnsImm, VirtReg, SignExtImm
+Index: 0 | 1 2 3 4 5
+Meaning: DestReg, | BaseReg, Scale, IndexReg, Displacement Segment
+OperandTy: VirtReg, | VirtReg, UnsImm, VirtReg, SignExtImm PhysReg
</pre>
</div>
<p>Stores, and all other instructions, treat the four memory operands in the
- same way and in the same order.</p>
+ same way and in the same order. If the segment register is unspecified
+ (regno = 0), then no segment override is generated. "Lea" operations do not
+ have a segment register specified, so they only have 4 operands for their
+ memory reference.</p>
</div>