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Instcombine: Fix pattern where the sext did not dominate the icmp using it 

llvm-svn: 123121
This commit is contained in:
Tobias Grosser 2011-01-09 16:00:11 +00:00
parent bc453f6e18
commit cc21c4aa98
2 changed files with 18 additions and 2 deletions
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9
llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -281,8 +281,8 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
Value *FalseVal = SI.getFalseValue(); Value *FalseVal = SI.getFalseValue();
// Check cases where the comparison is with a constant that // Check cases where the comparison is with a constant that
// can be adjusted to fit the min/max idiom. We may edit ICI in // can be adjusted to fit the min/max idiom. We may move or edit ICI
// place here, so make sure the select is the only user. // here, so make sure the select is the only user.
if (ICI->hasOneUse()) if (ICI->hasOneUse())
if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
// X < MIN ? T : F --> F // X < MIN ? T : F --> F
@ -364,6 +364,11 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
ICI->setOperand(1, CmpRHS); ICI->setOperand(1, CmpRHS);
SI.setOperand(1, TrueVal); SI.setOperand(1, TrueVal);
SI.setOperand(2, FalseVal); SI.setOperand(2, FalseVal);
// Move ICI instruction right before the select instruction. Otherwise
// the sext/zext value may be defined after the ICI instruction uses it.
ICI->moveBefore(&SI);
Changed = true; Changed = true;
break; break;
} }

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

@ -678,3 +678,14 @@ define i64 @test49(i32 %a) nounwind {
; CHECK-NEXT: %min = select i1 %is_a_nonpositive, i64 %a_ext, i64 2 ; CHECK-NEXT: %min = select i1 %is_a_nonpositive, i64 %a_ext, i64 2
; CHECK-NEXT: ret i64 %min ; CHECK-NEXT: ret i64 %min
} }
define i64 @test50(i32 %a) nounwind {
%is_a_nonpositive = icmp ult i32 %a, 3
%a_ext = sext i32 %a to i64
%min = select i1 %is_a_nonpositive, i64 2, i64 %a_ext
ret i64 %min
; CHECK: @test50
; CHECK-NEXT: %a_ext = sext i32 %a to i64
; CHECK-NEXT: %is_a_nonpositive = icmp ugt i64 %a_ext, 2
; CHECK-NEXT: %min = select i1 %is_a_nonpositive, i64 %a_ext, i64 2
; CHECK-NEXT: ret i64 %min
}