https://github.com/OCHyams created https://github.com/llvm/llvm-project/pull/149509
That's enabling Clang's -gkey-instructions, cc1's -gkey-instructions remains off by default. Key Instructions improves the optimized-code debug-stepping experience in debuggers that use DWARF's `is_stmt` line table register to determine stepping behaviour. The feature can be disabled with `-gno-key-instructions`. RFC: https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668 --- Questions: *LLDB* - I believe LLDB ignores Clang's `is_stmt`s for stepping, but I don't know whether moving `is_stmt`s around in ways LLDB hasn't seen before (at least as output from Clang) is going to have any unexpected consequences. cc @adrian-prantl @JDevlieghere for opinions - what testing and checking would be needed / possible here, to be confident that this doesn't break optimized code debugging for LLDB? *Clang languages/extensions* - I've implemented support for C/C++, but I've not tested or specifically implemented anything for other languages (?) or extensions (?) like CUDA. Is there a good way to filter for this in the driver code in this patch? >From 984de46013b14bec9c3759ef47a853940306ceca Mon Sep 17 00:00:00 2001 From: Orlando Cazalet-Hyams <orlando.hy...@sony.com> Date: Fri, 18 Jul 2025 13:34:07 +0100 Subject: [PATCH] [KeyInstr] Enable -gkey-instructions by default if optimisations are enabled Key Instructions improves the optimized-code debug-stepping experience in debuggers that use DWARF's `is_stmt` line table register to determine stepping behaviour. The feature can be disabled with `-gno-key-instructions`. RFC: https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668 --- clang/lib/Driver/ToolChains/Clang.cpp | 8 ++++- clang/test/DebugInfo/KeyInstructions/flag.cpp | 33 +++++++++++++++++-- 2 files changed, 38 insertions(+), 3 deletions(-) diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp index 8880c9375143f..38eebbd6f9b5f 100644 --- a/clang/lib/Driver/ToolChains/Clang.cpp +++ b/clang/lib/Driver/ToolChains/Clang.cpp @@ -4611,8 +4611,14 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T, CmdArgs.push_back("-gembed-source"); } + // Enable Key Instructions by default if optimisations are enabled and + // we're emitting DWARF. + Arg *OptLevel = Args.getLastArg(options::OPT_O_Group); + bool KeyInstructionsOnByDefault = + EmitDwarf && OptLevel && !OptLevel->getOption().matches(options::OPT_O0); if (Args.hasFlag(options::OPT_gkey_instructions, - options::OPT_gno_key_instructions, false)) + options::OPT_gno_key_instructions, + KeyInstructionsOnByDefault)) CmdArgs.push_back("-gkey-instructions"); if (EmitCodeView) { diff --git a/clang/test/DebugInfo/KeyInstructions/flag.cpp b/clang/test/DebugInfo/KeyInstructions/flag.cpp index e34faa6cbb347..05a34ac670feb 100644 --- a/clang/test/DebugInfo/KeyInstructions/flag.cpp +++ b/clang/test/DebugInfo/KeyInstructions/flag.cpp @@ -1,7 +1,5 @@ // RUN: %clang -### -target x86_64 -c -gdwarf -gkey-instructions %s 2>&1 | FileCheck %s --check-prefixes=KEY-INSTRUCTIONS // RUN: %clang -### -target x86_64 -c -gdwarf -gno-key-instructions %s 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS -//// Default: Off. -// RUN: %clang -### -target x86_64 -c -gdwarf %s 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS //// Help. // RUN %clang --help | FileCheck %s --check-prefix=HELP @@ -23,3 +21,34 @@ void f() {} // RUN: %clang_cc1 %s -triple x86_64-linux-gnu -gkey-instructions -debug-info-kind=line-tables-only -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-ON // SMOKETEST-ON: keyInstructions: true // SMOKETEST-ON: atomGroup: 1 + +//// Enable Key Instructions by default if optimisations are enabled and we're +//// emitting DWARF. +//// +//// | opt level | -gkey-instructions | feature | +//// | 0 | no | off | +//// | 0 | yes | on | +//// | >=1 | no | on | +//// | >=1 | yes | on | +//// | >=1 | no & no -g flags | off | +//// | >=1 | no & emit codeview | off | +// +// RUN: %clang %s -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS +// RUN: %clang %s -target x86_64 -gdwarf -gmlt -gkey-instructions -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS +// RUN: %clang %s -O0 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS +// RUN: %clang %s -O0 -target x86_64 -gdwarf -gmlt -gkey-instructions -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS +// RUN: %clang %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS +// RUN: %clang %s -O1 -target x86_64 -gdwarf -gmlt -gkey-instructions -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS +// RUN: %clang %s -O1 -target x86_64 -### 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS +// RUN: %clang %s -O1 -target x86_64 -gcodeview -gmlt -### 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS +// +// RUN: %clang %s -target x86_64 -gdwarf -gmlt -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-OFF +// RUN: %clang %s -target x86_64 -gdwarf -gmlt -gkey-instructions -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-ON +// RUN: %clang %s -O0 -target x86_64 -gdwarf -gmlt -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-OFF +// RUN: %clang %s -O0 -target x86_64 -gdwarf -gmlt -gkey-instructions -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-ON +// RUN: %clang %s -O1 -target x86_64 -gdwarf -gmlt -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-ON +// RUN: %clang %s -O1 -target x86_64 -gdwarf -gmlt -gkey-instructions -S -emit-llvm -o - | FileCheck %s --check-prefix=SMOKETEST-ON +// RUN: %clang %s -O1 -target x86_64 -S -emit-llvm -o - | FileCheck %s --check-prefixes=SMOKETEST-OFF,SMOKETEST-NO-DEBUG +// RUN: %clang %s -O1 -target x86_64 -gcodeview -gmlt -S -emit-llvm -o - | FileCheck %s --check-prefixes=SMOKETEST-OFF +// SMOKETEST-NO-DEBUG: llvm.module.flags +// SMOKETEST-NO-DEBUG-NOT: DICompileUnit _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
