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Transforms: Don't create bad weights when eliminating dead cases 

If we happen to eliminate every case in a switch that has branch
weights, we currently try to create metadata for the one remaining
branch, triggering an assert. Instead, we need to check that the
metadata we're trying to create is sensible.

llvm-svn: 197791
This commit is contained in:
Justin Bogner 2013-12-20 08:21:30 +00:00
parent 668eb1f746
commit 0ba3f211c4
2 changed files with 26 additions and 1 deletions
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2
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -3222,7 +3222,7 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI) {
Case.getCaseSuccessor()->removePredecessor(SI->getParent());
SI->removeCase(Case);
}
if (HasWeight) {
if (HasWeight && Weights.size() >= 2) {
SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
SI->setMetadata(LLVMContext::MD_prof,
MDBuilder(SI->getParent()->getContext()).

25
llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll
View File

@ -313,6 +313,31 @@ sw.epilog:
ret void
}
;; If every case is dead, make sure they are all removed. This used to
;; crash trying to merge the metadata.
define void @test13(i32 %x) nounwind {
entry:
%i = shl i32 %x, 1
switch i32 %i, label %a [
i32 21, label %b
i32 25, label %c
], !prof !8
; CHECK-LABEL: @test13(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @helper
; CHECK-NEXT: ret void
a:
call void @helper(i32 0) nounwind
ret void
b:
call void @helper(i32 1) nounwind
ret void
c:
call void @helper(i32 2) nounwind
ret void
}
!0 = metadata !{metadata !"branch_weights", i32 3, i32 5}
!1 = metadata !{metadata !"branch_weights", i32 1, i32 1}
!2 = metadata !{metadata !"branch_weights", i32 1, i32 2}