[LLVMdev] Question about the new version of LLVM GCC
sabre at nondot.org
Sun May 20 23:27:44 PDT 2007
On Sun, 20 May 2007, Ben Chambers wrote:
> I noticed the following line in the output of LLVM GCC and was
> wondering what it meant:
> "alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
> I wasn't aware that a string was a valid left hand side, but
LLVM allows arbitrary characters to be in the names of values. For simple
things, it uses %foo, for complex things, it uses quoted strings (in this
case, due to the space).
> considering the fact that the instruction is basically pointless
> (doesn't do anything, and is never used), I'm guessing that it instead
> serves to mark the end of the allocas for that function. Is this
> correct? If not, what does the instruction mean/do?
The LLVM APIs make it easy, fast and convenient to insert an instruction
before another one. The llvm-gcc f.e. uses this bitcast as an anchor to
insert (you guessed it) allocas.
More information about the llvm-dev