[llvm-commits] [llvm] r164054 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/preserve-branchweights.ll
Manman Ren
mren at apple.com
Mon Sep 17 14:30:40 PDT 2012
Author: mren
Date: Mon Sep 17 16:30:40 2012
New Revision: 164054
URL: http://llvm.org/viewvc/llvm-project?rev=164054&view=rev
Log:
PGO: preserve branch-weight metadata when simplifying two branches with a common
destination in SimplifyCondBranchToCondBranch.
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=164054&r1=164053&r2=164054&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Sep 17 16:30:40 2012
@@ -2150,6 +2150,33 @@
PBI->setSuccessor(0, CommonDest);
PBI->setSuccessor(1, OtherDest);
+ // Update branch weight for PBI.
+ uint64_t PredTrueWeight, PredFalseWeight, SuccTrueWeight, SuccFalseWeight;
+ bool PredHasWeights = ExtractBranchMetadata(PBI, PredTrueWeight,
+ PredFalseWeight);
+ bool SuccHasWeights = ExtractBranchMetadata(BI, SuccTrueWeight,
+ SuccFalseWeight);
+ if (PredHasWeights && SuccHasWeights) {
+ uint64_t PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight;
+ uint64_t PredOther = PBIOp ?PredTrueWeight : PredFalseWeight;
+ uint64_t SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight;
+ uint64_t SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight;
+ // The weight to CommonDest should be PredCommon * SuccTotal +
+ // PredOther * SuccCommon.
+ // The weight to OtherDest should be PredOther * SuccOther.
+ SmallVector<uint64_t, 2> NewWeights;
+ NewWeights.push_back(PredCommon * (SuccCommon + SuccOther) +
+ PredOther * SuccCommon);
+ NewWeights.push_back(PredOther * SuccOther);
+ // Halve the weights if any of them cannot fit in an uint32_t
+ FitWeights(NewWeights);
+
+ SmallVector<uint32_t, 2> MDWeights(NewWeights.begin(),NewWeights.end());
+ PBI->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(BI->getContext()).
+ createBranchWeights(MDWeights));
+ }
+
// OtherDest may have phi nodes. If so, add an entry from PBI's
// block that are identical to the entries for BI's block.
AddPredecessorToBlock(OtherDest, PBI->getParent(), BB);
Modified: llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll?rev=164054&r1=164053&r2=164054&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/preserve-branchweights.ll Mon Sep 17 16:30:40 2012
@@ -174,16 +174,37 @@
ret void
}
+define void @test7(i1 %a, i1 %b) {
+; CHECK: @test7
+entry:
+ %c = or i1 %b, false
+ br i1 %a, label %Y, label %X, !prof !0
+; CHECK: br i1 %brmerge, label %Y, label %Z, !prof !5
+
+X:
+ br i1 %c, label %Y, label %Z, !prof !6
+
+Y:
+ call void @helper(i32 0)
+ ret void
+
+Z:
+ call void @helper(i32 1)
+ 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}
!3 = metadata !{metadata !"branch_weights", i32 4, i32 3, i32 2, i32 1}
!4 = metadata !{metadata !"branch_weights", i32 4, i32 3, i32 2, i32 1}
!5 = metadata !{metadata !"branch_weights", i32 7, i32 6, i32 5}
+!6 = metadata !{metadata !"branch_weights", i32 1, i32 3}
; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11}
; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5}
; CHECK: !2 = metadata !{metadata !"branch_weights", i32 7, i32 1, i32 2}
; CHECK: !3 = metadata !{metadata !"branch_weights", i32 49, i32 12, i32 24, i32 35}
; CHECK: !4 = metadata !{metadata !"branch_weights", i32 11, i32 5}
-; CHECK-NOT: !5
+; CHECK: !5 = metadata !{metadata !"branch_weights", i32 17, i32 15}
+; CHECK-NOT: !6
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