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InstCombine: Turn _chk functions into the "unsafe" variant if length and max langth are equal. 

This happens when we take the (non-constant) length from a malloc.

llvm-svn: 122961
This commit is contained in:
Benjamin Kramer 2011-01-06 14:22:52 +00:00
parent 605f21a6c8
commit ae67cc13a9
2 changed files with 13 additions and 0 deletions
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2
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -722,6 +722,8 @@ protected:
NewInstruction = IC->ReplaceInstUsesWith(*CI, With);
}
bool isFoldable(unsigned SizeCIOp, unsigned SizeArgOp, bool isString) const {
if (CI->getArgOperand(SizeCIOp) == CI->getArgOperand(SizeArgOp))
return true;
if (ConstantInt *SizeCI =
dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp))) {
if (SizeCI->isAllOnesValue())

11
llvm/test/Transforms/InstCombine/objsize.ll
View File

@ -176,3 +176,14 @@ define i32 @test9(i32 %x) {
; CHECK-NOT: ret i32 %x
ret i32 %objsize
}
define i8* @test10(i32 %x) {
; CHECK: @test10
%alloc = call noalias i8* @malloc(i32 %x) nounwind
%objsize = call i32 @llvm.objectsize.i32(i8* %alloc, i1 false) nounwind readonly
tail call i8* @__memset_chk(i8* %alloc, i32 0, i32 %x, i32 %objsize) nounwind
; CHECK-NOT: @llvm.objectsize
; CHECK: @llvm.memset
ret i8* %alloc
; CHECK: ret i8*
}