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Transforms: Don't create bad branch weights when folding a switch

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This avoids creating branch weight metadata of length one when we fold
cases into the default of a switch instruction, which was triggering
an assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196845 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Justin Bogner 2013-12-10 00:13:41 +00:00
parent 4a644cc525
commit 31eaed9c6d
2 changed files with 22 additions and 2 deletions
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6
lib/Transforms/Utils/Local.cpp
View File

@ -127,8 +127,10 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
// dest. If so, eliminate it as an explicit compare.
if (i.getCaseSuccessor() == DefaultDest) {
MDNode* MD = SI->getMetadata(LLVMContext::MD_prof);
// MD should have 2 + NumCases operands.
if (MD && MD->getNumOperands() == 2 + SI->getNumCases()) {
unsigned NCases = SI->getNumCases();
// Fold the case metadata into the default if there will be any branches
// left, unless the metadata doesn't match the switch.
if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
// Collect branch weights into a vector.
SmallVector<uint32_t, 8> Weights;
for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;

18
test/Transforms/SimplifyCFG/preserve-branchweights.ll
View File

@ -293,6 +293,23 @@ c:
ret void
}
;; test12 - Don't crash if the whole switch is removed
define void @test12(i32 %M, i32 %N) nounwind uwtable {
entry:
switch i32 %N, label %sw.bb [
i32 1, label %sw.bb
], !prof !9
; CHECK: test12
; CHECK-NOT: switch
sw.bb:
call void @helper(i32 0)
br label %sw.epilog
sw.epilog:
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}
@ -302,6 +319,7 @@ c:
!6 = metadata !{metadata !"branch_weights", i32 1, i32 3}
!7 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8, i32 7}
!8 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8}
!9 = metadata !{metadata !"branch_weights", i32 7, i32 6}
; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11}
; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5}