From 3e48c8d75d1ca937ab3595909fb4198226c4ad1d Mon Sep 17 00:00:00 2001 From: OCHyams Date: Wed, 22 Feb 2023 16:29:44 +0000 Subject: [PATCH] [Assignment Tracking] Only set module flag if pass modifies a function The module flag "debug-info-assignment-tracking" is set by the declare-to-assign pass to indicate that assignment tracking is enabled. This patch changes declare-to-assign to only set the flag if it makes a modification. This lets the compiler avoid doing extra work for no benefit, such as is currently the case if assignment tracking is requested for a build with line tables only (-gmlt) or a build without debug info. Reviewed By: scott.linder Differential Revision: https://reviews.llvm.org/D144481 --- llvm/include/llvm/IR/DebugInfo.h | 2 +- llvm/lib/IR/DebugInfo.cpp | 14 +++++-- .../declare-to-assign/set-flag-only-if-modified.ll | 47 ++++++++++++++++++++++ 3 files changed, 59 insertions(+), 4 deletions(-) create mode 100644 llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/set-flag-only-if-modified.ll diff --git a/llvm/include/llvm/IR/DebugInfo.h b/llvm/include/llvm/IR/DebugInfo.h index 5e62d87..4b3c3a6 100644 --- a/llvm/include/llvm/IR/DebugInfo.h +++ b/llvm/include/llvm/IR/DebugInfo.h @@ -296,7 +296,7 @@ std::optional getAssignmentInfo(const DataLayout &DL, class AssignmentTrackingPass : public PassInfoMixin { /// Note: this method does not set the debug-info-assignment-tracking module /// flag. - void runOnFunction(Function &F); + bool runOnFunction(Function &F); public: PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp index c601dbf..d3e7c25 100644 --- a/llvm/lib/IR/DebugInfo.cpp +++ b/llvm/lib/IR/DebugInfo.cpp @@ -1963,7 +1963,8 @@ void at::trackAssignments(Function::iterator Start, Function::iterator End, } } -void AssignmentTrackingPass::runOnFunction(Function &F) { +bool AssignmentTrackingPass::runOnFunction(Function &F) { + bool Changed = false; // Collect a map of {backing storage : dbg.declares} (currently "backing // storage" is limited to Allocas). We'll use this to find dbg.declares to // delete after running `trackAssignments`. @@ -2016,8 +2017,10 @@ void AssignmentTrackingPass::runOnFunction(Function &F) { // Delete DDI because the variable location is now tracked using // assignment tracking. DDI->eraseFromParent(); + Changed = true; } } + return Changed; } static const char *AssignmentTrackingModuleFlag = @@ -2040,7 +2043,8 @@ bool llvm::isAssignmentTrackingEnabled(const Module &M) { PreservedAnalyses AssignmentTrackingPass::run(Function &F, FunctionAnalysisManager &AM) { - runOnFunction(F); + if (!runOnFunction(F)) + return PreservedAnalyses::all(); // Record that this module uses assignment tracking. It doesn't matter that // some functons in the module may not use it - the debug info in those @@ -2056,8 +2060,12 @@ PreservedAnalyses AssignmentTrackingPass::run(Function &F, PreservedAnalyses AssignmentTrackingPass::run(Module &M, ModuleAnalysisManager &AM) { + bool Changed = false; for (auto &F : M) - runOnFunction(F); + Changed |= runOnFunction(F); + + if (!Changed) + return PreservedAnalyses::all(); // Record that this module uses assignment tracking. setAssignmentTrackingModuleFlag(M); diff --git a/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/set-flag-only-if-modified.ll b/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/set-flag-only-if-modified.ll new file mode 100644 index 0000000..3481bfe --- /dev/null +++ b/llvm/test/DebugInfo/Generic/assignment-tracking/declare-to-assign/set-flag-only-if-modified.ll @@ -0,0 +1,47 @@ +; RUN: opt -passes=declare-to-assign -S %s -o - \ +; RUN: | FileCheck %s --check-prefix=WITHOUT-INTRINSIC + +; RUN: sed 's/;Uncomment-with-sed//g' < %s \ +; RUN: | opt -passes=declare-to-assign -S - -o - \ +; RUN: | FileCheck %s --check-prefix=WITH-INTRINSIC + +; WITHOUT-INTRINSIC-NOT: "debug-info-assignment-tracking" +; WITH-INTRINSIC: "debug-info-assignment-tracking" + +;; Check that the module flag "debug-info-assignment-tracking" is only added if +;; declare-to-assign actually modifies the function. In the first run the +;; dbg.declare is commented out and the pass leaves the function unmodified. +;; In the second run sed is used to uncomment the dbg.declare and +;; declare-to-assign replaces it with a dbg.assign. + +define dso_local void @f() !dbg !9 { +entry: + %a = alloca i32, align 4 +;Uncomment-with-sed call void @llvm.dbg.declare(metadata ptr %a, metadata !13, metadata !DIExpression()), !dbg !16 + ret void, !dbg !17 +} + +declare void @llvm.dbg.declare(metadata, metadata, metadata) + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!2, !3, !4, !5, !6, !7} +!llvm.ident = !{!8} + +!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 17.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None) +!1 = !DIFile(filename: "test.c", directory: "/") +!2 = !{i32 7, !"Dwarf Version", i32 5} +!3 = !{i32 2, !"Debug Info Version", i32 3} +!4 = !{i32 1, !"wchar_size", i32 4} +!5 = !{i32 8, !"PIC Level", i32 2} +!6 = !{i32 7, !"PIE Level", i32 2} +!7 = !{i32 7, !"uwtable", i32 2} +!8 = !{!"clang version 17.0.0"} +!9 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 1, type: !10, scopeLine: 1, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12) +!10 = !DISubroutineType(types: !11) +!11 = !{null} +!12 = !{!13} +!13 = !DILocalVariable(name: "a", scope: !9, file: !1, line: 1, type: !14) +!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!15 = !DILocation(line: 1, column: 12, scope: !9) +!16 = !DILocation(line: 1, column: 16, scope: !9) +!17 = !DILocation(line: 1, column: 19, scope: !9) -- 2.7.4