From f3aefca7c1bcdd3a6445b7ae04a9f69af567a7e7 Mon Sep 17 00:00:00 2001 From: Justin Bogner Date: Fri, 4 Apr 2014 02:48:51 +0000 Subject: [PATCH] CodeGen: Don't create branch weight metadata from empty profiles If all of our weights are zero when calculating branch weights, it means we haven't profiled the code in question. Avoid creating a metadata node that says all branches are equally likely in this case. The test also checks constructs that hit the other createBranchWeights overload. These were already working. llvm-svn: 205606 --- clang/lib/CodeGen/CodeGenPGO.cpp | 8 ++- .../Profile/Inputs/c-unprofiled-blocks.profdata | 32 ++++++++++ clang/test/Profile/c-unprofiled-blocks.c | 68 ++++++++++++++++++++++ 3 files changed, 106 insertions(+), 2 deletions(-) create mode 100644 clang/test/Profile/Inputs/c-unprofiled-blocks.profdata create mode 100644 clang/test/Profile/c-unprofiled-blocks.c diff --git a/clang/lib/CodeGen/CodeGenPGO.cpp b/clang/lib/CodeGen/CodeGenPGO.cpp index ac6b7bc..935724f 100644 --- a/clang/lib/CodeGen/CodeGenPGO.cpp +++ b/clang/lib/CodeGen/CodeGenPGO.cpp @@ -1004,9 +1004,13 @@ llvm::MDNode *CodeGenPGO::createBranchWeights(ArrayRef Weights) { if (Weights.size() < 2) return nullptr; + // Check for empty weights. + uint64_t MaxWeight = *std::max_element(Weights.begin(), Weights.end()); + if (MaxWeight == 0) + return nullptr; + // Calculate how to scale down to 32-bits. - uint64_t Scale = calculateWeightScale(*std::max_element(Weights.begin(), - Weights.end())); + uint64_t Scale = calculateWeightScale(MaxWeight); SmallVector ScaledWeights; ScaledWeights.reserve(Weights.size()); diff --git a/clang/test/Profile/Inputs/c-unprofiled-blocks.profdata b/clang/test/Profile/Inputs/c-unprofiled-blocks.profdata new file mode 100644 index 0000000..bf2158a --- /dev/null +++ b/clang/test/Profile/Inputs/c-unprofiled-blocks.profdata @@ -0,0 +1,32 @@ +never_called +9 +9 +0 +0 +0 +0 +0 +0 +0 +0 +0 + +main +1 +1 +1 + +dead_code +10 +10 +1 +0 +0 +0 +0 +0 +0 +0 +0 +0 + diff --git a/clang/test/Profile/c-unprofiled-blocks.c b/clang/test/Profile/c-unprofiled-blocks.c new file mode 100644 index 0000000..1f75a0d --- /dev/null +++ b/clang/test/Profile/c-unprofiled-blocks.c @@ -0,0 +1,68 @@ +// Blocks that we have no profile data for (ie, it was never reached in training +// runs) shouldn't have any branch weight metadata added. + +// RUN: %clang_cc1 -triple x86_64-apple-macosx10.9 -main-file-name c-unprofiled-blocks.c %s -o - -emit-llvm -fprofile-instr-use=%S/Inputs/c-unprofiled-blocks.profdata | FileCheck -check-prefix=PGOUSE %s + +// PGOUSE-LABEL: @never_called(i32 %i) +int never_called(int i) { + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + if (i) {} + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + for (i = 0; i < 100; ++i) { + } + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + while (--i) {} + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + do {} while (i++ < 75); + + // PGOUSE: switch {{.*}} [ + // PGOUSE-NEXT: i32 12 + // PGOUSE-NEXT: i32 82 + // PGOUSE-NEXT: ]{{$}} + switch (i) { + case 12: return 3; + case 82: return 0; + default: return 89; + } +} + +// PGOUSE-LABEL: @dead_code(i32 %i) +int dead_code(int i) { + // PGOUSE: br {{.*}}, !prof !{{[0-9]+}} + if (i) { + // This branch is never reached. + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + if (!i) {} + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + for (i = 0; i < 100; ++i) { + } + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + while (--i) {} + + // PGOUSE: br i1 %{{[^,]*}}, label %{{[^,]*}}, label %{{[^,]*}}{{$}} + do {} while (i++ < 75); + + // PGOUSE: switch {{.*}} [ + // PGOUSE-NEXT: i32 12 + // PGOUSE-NEXT: i32 82 + // PGOUSE-NEXT: ]{{$}} + switch (i) { + case 12: return 3; + case 82: return 0; + default: return 89; + } + } + return 2; +} + +// PGOUSE-LABEL: @main(i32 %argc, i8** %argv) +int main(int argc, const char *argv[]) { + dead_code(0); + return 0; +} -- 2.7.4