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[CGP] avoid crashing from weightlessness 

It's possible that we have branch weights with 0 values.
In that case, don't try to create an impossible BranchProbability.

llvm-svn: 268935
This commit is contained in:
Sanjay Patel 2016-05-09 17:31:55 +00:00
parent b5935bfd7d
commit c7b91e65d8
2 changed files with 19 additions and 3 deletions
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8
llvm/lib/CodeGen/CodeGenPrepare.cpp
View File

@ -4559,9 +4559,11 @@ static bool isFormingBranchFromSelectProfitable(const TargetTransformInfo *TTI,
if (SI->extractProfMetadata(TrueWeight, FalseWeight)) {
uint64_t Max = std::max(TrueWeight, FalseWeight);
uint64_t Sum = TrueWeight + FalseWeight;
auto Probability = BranchProbability::getBranchProbability(Max, Sum);
if (Probability > TLI->getPredictableBranchThreshold())
return true;
if (Sum != 0) {
auto Probability = BranchProbability::getBranchProbability(Max, Sum);
if (Probability > TLI->getPredictableBranchThreshold())
return true;
}
}
CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());

14
llvm/test/CodeGen/X86/cmov-into-branch.ll
View File

@ -114,8 +114,22 @@ define i32 @weighted_select3(i32 %a, i32 %b) {
ret i32 %sel
}
; Weightlessness is no reason to die.
define i32 @unweighted_select(i32 %a, i32 %b) {
; CHECK-LABEL: unweighted_select:
; CHECK: # BB#0:
; CHECK-NEXT: testl %edi, %edi
; CHECK-NEXT: cmovnel %edi, %esi
; CHECK-NEXT: movl %esi, %eax
; CHECK-NEXT: retq
;
%cmp = icmp ne i32 %a, 0
%sel = select i1 %cmp, i32 %a, i32 %b, !prof !3
ret i32 %sel
}
!0 = !{!"branch_weights", i32 1, i32 99}
!1 = !{!"branch_weights", i32 1, i32 100}
!2 = !{!"branch_weights", i32 100, i32 1}
!3 = !{!"branch_weights", i32 0, i32 0}