diff options
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 25 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/preserve-branchweights.ll | 32 |
2 files changed, 44 insertions, 13 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index e43c9e2708..0401b9a7f7 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -748,21 +748,22 @@ static void GetBranchWeights(TerminatorInst *TI, } } -/// Sees if any of the weights are too big for a uint32_t, and halves all the -/// weights if any are. +/// Keep halving the weights until all can fit in uint32_t. static void FitWeights(MutableArrayRef<uint64_t> Weights) { - bool Halve = false; - for (unsigned i = 0; i < Weights.size(); ++i) - if (Weights[i] > UINT_MAX) { - Halve = true; - break; - } + while (true) { + bool Halve = false; + for (unsigned i = 0; i < Weights.size(); ++i) + if (Weights[i] > UINT_MAX) { + Halve = true; + break; + } - if (! Halve) - return; + if (! Halve) + return; - for (unsigned i = 0; i < Weights.size(); ++i) - Weights[i] /= 2; + for (unsigned i = 0; i < Weights.size(); ++i) + Weights[i] /= 2; + } } /// FoldValueComparisonIntoPredecessors - The specified terminator is a value diff --git a/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/test/Transforms/SimplifyCFG/preserve-branchweights.ll index 67f5636573..bdd25ba805 100644 --- a/test/Transforms/SimplifyCFG/preserve-branchweights.ll +++ b/test/Transforms/SimplifyCFG/preserve-branchweights.ll @@ -338,6 +338,32 @@ c: ret void } +;; When folding branches to common destination, the updated branch weights +;; can exceed uint32 by more than factor of 2. We should keep halving the +;; weights until they can fit into uint32. +@max_regno = common global i32 0, align 4 +define void @test14(i32* %old, i32 %final) { +; CHECK-LABEL: @test14 +; CHECK: br i1 %or.cond, label %for.exit, label %for.inc, !prof !10 +for.cond: + br label %for.cond2 +for.cond2: + %i.1 = phi i32 [ %inc19, %for.inc ], [ 0, %for.cond ] + %bit.0 = phi i32 [ %shl, %for.inc ], [ 1, %for.cond ] + %tobool = icmp eq i32 %bit.0, 0 + br i1 %tobool, label %for.exit, label %for.body3, !prof !10 +for.body3: + %v3 = load i32* @max_regno, align 4 + %cmp4 = icmp eq i32 %i.1, %v3 + br i1 %cmp4, label %for.exit, label %for.inc, !prof !11 +for.inc: + %shl = shl i32 %bit.0, 1 + %inc19 = add nsw i32 %i.1, 1 + br label %for.cond2 +for.exit: + 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} @@ -348,6 +374,8 @@ c: !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} +!10 = metadata !{metadata !"branch_weights", i32 672646, i32 21604207} +!11 = metadata !{metadata !"branch_weights", i32 6960, i32 21597248} ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11} ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5} @@ -359,4 +387,6 @@ c: ; CHECK: !7 = metadata !{metadata !"branch_weights", i32 17, i32 9, i32 8, i32 7, i32 17} ; CHECK: !8 = metadata !{metadata !"branch_weights", i32 24, i32 33} ; CHECK: !9 = metadata !{metadata !"branch_weights", i32 8, i32 33} -; CHECK-NOT: !9 +;; The false weight prints out as a negative integer here, but inside llvm, we +;; treat the weight as an unsigned integer. +; CHECK: !10 = metadata !{metadata !"branch_weights", i32 112017436, i32 -735157296} |