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[KeyInstr] Enable -gkey-instructions by default if optimisations are enabled #149509

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Merged
merged 3 commits into from
Aug 27, 2025
Merged

[KeyInstr] Enable -gkey-instructions by default if optimisations are enabled #149509

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984de46
[KeyInstr] Enable -gkey-instructions by default if optimisations are …
OCHyams Jul 18, 2025
9a6d8b2
Only enable for 'plain' C/C++
OCHyams Aug 26, 2025
8901c72
Merge branch 'main' into ki-conditional-default
OCHyams Aug 26, 2025
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22 changes: 17 additions & 5 deletions clang/lib/Driver/ToolChains/Clang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4394,10 +4394,15 @@ static void renderDwarfFormat(const Driver &D, const llvm::Triple &T,

static void
renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
const ArgList &Args, bool IRInput, ArgStringList &CmdArgs,
const InputInfo &Output,
const ArgList &Args, types::ID InputType,
ArgStringList &CmdArgs, const InputInfo &Output,
llvm::codegenoptions::DebugInfoKind &DebugInfoKind,
DwarfFissionKind &DwarfFission) {
bool IRInput = isLLVMIR(InputType);
bool PlainCOrCXX = isDerivedFromC(InputType) && !isCuda(InputType) &&
!isHIP(InputType) && !isObjC(InputType) &&
!isOpenCL(InputType);
Comment on lines +4401 to +4404
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Obvious question, is there a better way of selecting "just C and C++" rather than "list of extensions that this shouldn't apply to"?

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I don't love it either, but I couldn't find a better way. I asked for advice in the pull request description and a comment - I'll happily take suggestions if anyone has any! Are you happy for this to go in as-is?

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Should be fine IMO.


if (Args.hasFlag(options::OPT_fdebug_info_for_profiling,
options::OPT_fno_debug_info_for_profiling, false) &&
checkDebugInfoOption(
Expand Down Expand Up @@ -4591,8 +4596,15 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
CmdArgs.push_back("-gembed-source");
}

// Enable Key Instructions by default if we're emitting DWARF, the language is
// plain C or C++, and optimisations are enabled.
Arg *OptLevel = Args.getLastArg(options::OPT_O_Group);
bool KeyInstructionsOnByDefault =
EmitDwarf && PlainCOrCXX && 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) {
Expand Down Expand Up @@ -6060,8 +6072,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
llvm::codegenoptions::DebugInfoKind DebugInfoKind =
llvm::codegenoptions::NoDebugInfo;
DwarfFissionKind DwarfFission = DwarfFissionKind::None;
renderDebugOptions(TC, D, RawTriple, Args, types::isLLVMIR(InputType),
CmdArgs, Output, DebugInfoKind, DwarfFission);
renderDebugOptions(TC, D, RawTriple, Args, InputType, CmdArgs, Output,
DebugInfoKind, DwarfFission);

// Add the split debug info name to the command lines here so we
// can propagate it to the backend.
Expand Down
42 changes: 40 additions & 2 deletions clang/test/DebugInfo/KeyInstructions/flag.cpp
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@@ -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
Expand All @@ -23,3 +21,43 @@ 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

//// Check only "plain" C/C++ turns on Key Instructions by default.
// RUN: %clang -x c %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS
// RUN: %clang -x c++ %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=KEY-INSTRUCTIONS
// RUN: %clang -x cuda -nocudalib -nocudainc %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS
// RUN: %clang -x hip -nogpulib -nogpuinc %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS
// RUN: %clang -x cl %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS
// RUN: %clang -x objective-c %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS
// RUN: %clang -x objective-c++ %s -O1 -target x86_64 -gdwarf -gmlt -### 2>&1 | FileCheck %s --check-prefix=NO-KEY-INSTRUCTIONS