LangRef.rst: Clarify how basic blocks without named label are handled.

Describe that they are assigned numbered label using the same counter
as for unnamed temporaries.

Based on http://llvm.org/bugs/show_bug.cgi?id=16043 and mailing list
discussion.

Patch by Paul Sokolovsky!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182332 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index 4d006f135c1c867d62648504e9b07d578206a29d..4eecd15a6fc43978cab28ccc547ae3e4d5cf3b49 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -127,7 +127,8 @@ lexical features of LLVM:
 #. Comments are delimited with a '``;``' and go until the end of line.
 #. Unnamed temporaries are created when the result of a computation is
    not assigned to a named value.
-#. Unnamed temporaries are numbered sequentially
+#. Unnamed temporaries are numbered sequentially (using a per-function
+   incrementing counter, starting with 0).
 
 It also shows a convention that we follow in this document. When
 demonstrating instructions, we will follow an instruction with a comment
@@ -563,7 +564,11 @@ A function definition contains a list of basic blocks, forming the CFG
 start with a label (giving the basic block a symbol table entry),
 contains a list of instructions, and ends with a
 :ref:`terminator <terminators>` instruction (such as a branch or function
-return).
+return). If explicit label is not provided, a block is assigned an
+implicit numbered label, using a next value from the same counter as used
+for unnamed temporaries (:ref:`see above<identifiers>`). For example, if a
+function entry block does not have explicit label, it will be assigned
+label "%0", then first unnamed temporary in that block will be "%1", etc.
 
 The first basic block in a function is special in two ways: it is
 immediately executed on entrance to the function, and it is not allowed