RPCSX/llvm
1
0
Fork 0
mirror of https://github.com/RPCSX/llvm.git synced 2024-11-29 14:40:25 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

InstCombine: FoldGEPICmp shouldn't change sign of base pointer comparison

Browse Source 
Changing the sign when comparing the base pointer would introduce all
sorts of unexpected things like:
  %gep.i = getelementptr inbounds [1 x i8]* %a, i32 0, i32 0
  %gep2.i = getelementptr inbounds [1 x i8]* %b, i32 0, i32 0
  %cmp.i = icmp ult i8* %gep.i, %gep2.i
  %cmp.i1 = icmp ult [1 x i8]* %a, %b
  %cmp = icmp ne i1 %cmp.i, %cmp.i1
  ret i1 %cmp

into:
  %cmp.i = icmp slt [1 x i8]* %a, %b
  %cmp.i1 = icmp ult [1 x i8]* %a, %b
  %cmp = xor i1 %cmp.i, %cmp.i1
  ret i1 %cmp

By preserving the original sign, we now get:
  ret i1 false

This fixes PR16483.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185259 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2013-06-29 10:28:04 +00:00
parent df703257c1
commit c22a4eeec6
2 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -647,8 +647,7 @@ Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
// If all indices are the same, just compare the base pointers.
if (IndicesTheSame)
return new ICmpInst(ICmpInst::getSignedPredicate(Cond),
GEPLHS->getOperand(0), GEPRHS->getOperand(0));
return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
// If we're comparing GEPs with two base pointers that only differ in type
// and both GEPs have only constant indices or just one use, then fold

10
test/Transforms/InstCombine/getelementptr.ll
View File

@ -509,4 +509,14 @@ define void @test39(%struct.ham* %arg, i8 %arg1) nounwind {
; CHECK: getelementptr inbounds i8* %tmp3, i64 -8
}
define i1 @pr16483([1 x i8]* %a, [1 x i8]* %b) {
%c = getelementptr [1 x i8]* %a, i32 0, i32 0
%d = getelementptr [1 x i8]* %b, i32 0, i32 0
%cmp = icmp ult i8* %c, %d
ret i1 %cmp
; CHECK: @pr16483
; CHECK-NEXT: icmp ult [1 x i8]* %a, %b
}
; CHECK: attributes [[NUW]] = { nounwind }