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

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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
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Sean Silva 2013-05-20 23:31:12 +00:00
parent 7b72cc7782
commit 57f429fcac
1 changed files with 7 additions and 2 deletions
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@ -127,7 +127,8 @@ lexical features of LLVM:
#. Comments are delimited with a '``;``' and go until the end of line. #. Comments are delimited with a '``;``' and go until the end of line.
#. Unnamed temporaries are created when the result of a computation is #. Unnamed temporaries are created when the result of a computation is
not assigned to a named value. 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 It also shows a convention that we follow in this document. When
demonstrating instructions, we will follow an instruction with a comment 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), start with a label (giving the basic block a symbol table entry),
contains a list of instructions, and ends with a contains a list of instructions, and ends with a
:ref:`terminator <terminators>` instruction (such as a branch or function :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 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 immediately executed on entrance to the function, and it is not allowed