From 53a0c082d2f8e3dbd2e138adc7d0f60e46fed307 Mon Sep 17 00:00:00 2001 From: Dehao Chen Date: Thu, 23 Mar 2017 14:43:10 +0000 Subject: [PATCH] Do not set branch weight if the branch weight annotation is present. Summary: ThinLTO will annotate the CFG twice. If the branch weight is set by the first annotation, we should not set the branch weight again in the second annotation because the first annotation is more accurate as there is less optimization that could affect debug info accuracy. Reviewers: tejohnson, davidxl Reviewed By: tejohnson Subscribers: mehdi_amini, aprantl, llvm-commits Differential Revision: https://reviews.llvm.org/D31228 llvm-svn: 298602 --- llvm/lib/Transforms/IPO/SampleProfile.cpp | 6 +++++- llvm/test/Transforms/SampleProfile/branch.ll | 5 ++++- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp index e8a1acf..d2ccbd8 100644 --- a/llvm/lib/Transforms/IPO/SampleProfile.cpp +++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp @@ -1162,9 +1162,13 @@ void SampleProfileLoader::propagateWeights(Function &F) { } } + uint64_t TempWeight; // Only set weights if there is at least one non-zero weight. // In any other case, let the analyzer set weights. - if (MaxWeight > 0) { + // Do not set weights if the weights are present. In ThinLTO, the profile + // annotation is done twice. If the first annotation already set the + // weights, the second pass does not need to set it. + if (MaxWeight > 0 && !TI->extractProfTotalWeight(TempWeight)) { DEBUG(dbgs() << "SUCCESS. Found non-zero weights.\n"); TI->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights(Weights)); diff --git a/llvm/test/Transforms/SampleProfile/branch.ll b/llvm/test/Transforms/SampleProfile/branch.ll index 2ef01a7..5a5160e 100644 --- a/llvm/test/Transforms/SampleProfile/branch.ll +++ b/llvm/test/Transforms/SampleProfile/branch.ll @@ -87,7 +87,9 @@ for.cond: ; preds = %for.inc, %if.then.2 %6 = load i32, i32* %u, align 4, !dbg !46 %7 = load i32, i32* %limit, align 4, !dbg !48 %cmp5 = icmp slt i32 %6, %7, !dbg !49 - br i1 %cmp5, label %for.body, label %for.end, !dbg !50 + br i1 %cmp5, label %for.body, label %for.end, !dbg !50, !prof !80 +; CHECK: edge for.cond -> for.body probability is 0x73333333 / 0x80000000 = 90.00% +; CHECK: edge for.cond -> for.end probability is 0x0ccccccd / 0x80000000 = 10.00% for.body: ; preds = %for.cond call void @llvm.dbg.declare(metadata double* %x, metadata !51, metadata !17), !dbg !53 @@ -237,3 +239,4 @@ attributes #4 = { nounwind readonly } !77 = !DILocation(line: 20, column: 4, scope: !6) !78 = !DILocation(line: 21, column: 4, scope: !6) !79 = !DILocation(line: 22, column: 2, scope: !6) +!80 = !{!"branch_weights", i32 90, i32 10} -- 2.7.4