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[OpenMP][clang] 6.0: num_threads strict (part 3: codegen) #146405

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16db966
[OpenMP][clang] 6.0: num_threads strict (part 3: codegen)
ro-i Jun 27, 2025
8296fde
GPU codegen doesn't use emitNumThreadsClause -> pass information to e…
ro-i Jul 1, 2025
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61 changes: 38 additions & 23 deletions clang/lib/CodeGen/CGOpenMPRuntime.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1845,11 +1845,11 @@ void CGOpenMPRuntime::emitIfClause(CodeGenFunction &CGF, const Expr *Cond,
CGF.EmitBlock(ContBlock, /*IsFinished=*/true);
}

void CGOpenMPRuntime::emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond,
llvm::Value *NumThreads) {
void CGOpenMPRuntime::emitParallelCall(
CodeGenFunction &CGF, SourceLocation Loc, llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond,
llvm::Value *NumThreads, OpenMPNumThreadsClauseModifier NumThreadsModifier,
OpenMPSeverityClauseKind Severity, const Expr *Message) {
if (!CGF.HaveInsertPoint())
return;
llvm::Value *RTLoc = emitUpdateLocation(CGF, Loc);
Expand Down Expand Up @@ -2699,18 +2699,33 @@ llvm::Value *CGOpenMPRuntime::emitForNext(CodeGenFunction &CGF,
CGF.getContext().BoolTy, Loc);
}

void CGOpenMPRuntime::emitNumThreadsClause(CodeGenFunction &CGF,
llvm::Value *NumThreads,
SourceLocation Loc) {
void CGOpenMPRuntime::emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier, OpenMPSeverityClauseKind Severity,
const Expr *Message) {
if (!CGF.HaveInsertPoint())
return;
llvm::SmallVector<llvm::Value *, 4> Args(
{emitUpdateLocation(CGF, Loc), getThreadID(CGF, Loc),
CGF.Builder.CreateIntCast(NumThreads, CGF.Int32Ty, /*isSigned*/ true)});
// Build call __kmpc_push_num_threads(&loc, global_tid, num_threads)
llvm::Value *Args[] = {
emitUpdateLocation(CGF, Loc), getThreadID(CGF, Loc),
CGF.Builder.CreateIntCast(NumThreads, CGF.Int32Ty, /*isSigned*/ true)};
CGF.EmitRuntimeCall(OMPBuilder.getOrCreateRuntimeFunction(
CGM.getModule(), OMPRTL___kmpc_push_num_threads),
Args);
// or __kmpc_push_num_threads_strict(&loc, global_tid, num_threads, severity,
// messsage) if strict modifier is used.
RuntimeFunction FnID = OMPRTL___kmpc_push_num_threads;
if (Modifier == OMPC_NUMTHREADS_strict) {
FnID = OMPRTL___kmpc_push_num_threads_strict;
// OpenMP 6.0, 10.4: "If no severity clause is specified then the effect is
// as if sev-level is fatal."
Args.push_back(llvm::ConstantInt::get(
CGM.Int32Ty, Severity == OMPC_SEVERITY_warning ? 1 : 2));
if (Message)
Args.push_back(CGF.EmitStringLiteralLValue(cast<StringLiteral>(Message))
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What if the message is not a string literal?

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Currently, the message clause (which is also used for the error directive) only supports string literals:

llvm-project/clang/lib/Sema/SemaOpenMP.cpp

Lines 16447 to 16452 in e94bc16

assert(ME && "NULL expr in Message clause");
if (!isa<StringLiteral>(ME)) {
Diag(ME->getBeginLoc(), diag::warn_clause_expected_string)
<< getOpenMPClauseNameForDiag(OMPC_message);
return nullptr;
}

String literal is also assumed for the error directive's codegen:

llvm-project/clang/lib/CodeGen/CGOpenMPRuntime.cpp

Lines 2375 to 2378 in 5c7c855

llvm::Value *MVL =
ME ? CGF.EmitStringLiteralLValue(cast<StringLiteral>(ME)).getPointer(CGF)
: llvm::ConstantPointerNull::get(CGF.VoidPtrTy);
// Build call void __kmpc_error(ident_t *loc, int severity, const char

I can make a follow-up PR for that after we're done with this one. (Afaiu, the spec does not restrict the argument of the message clause to a string literal.)

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Can you generalize it here now and then fix sema analysis?

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Principally yes, I just played a bit with this. However, I think it's not entirely trivial, at least if we'd like to support a bit more than just const char * (e.g. char []). And, at least in 6.0, I think we should. (?) So that would preferably be a separate function EmitMessageClause that can be used by the error directive and the num_threads clause. As such, it would also need appropriate testing, which I can only add as soon as the sema change is made as well.

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This casting should be performed in Sem, so, you should expect expression of type const char * here

.getPointer(CGF));
else
Args.push_back(llvm::ConstantPointerNull::get(CGF.VoidPtrTy));
}
CGF.EmitRuntimeCall(
OMPBuilder.getOrCreateRuntimeFunction(CGM.getModule(), FnID), Args);
}

void CGOpenMPRuntime::emitProcBindClause(CodeGenFunction &CGF,
Expand Down Expand Up @@ -12030,12 +12045,11 @@ llvm::Function *CGOpenMPSIMDRuntime::emitTaskOutlinedFunction(
llvm_unreachable("Not supported in SIMD-only mode");
}

void CGOpenMPSIMDRuntime::emitParallelCall(CodeGenFunction &CGF,
SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond,
llvm::Value *NumThreads) {
void CGOpenMPSIMDRuntime::emitParallelCall(
CodeGenFunction &CGF, SourceLocation Loc, llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond,
llvm::Value *NumThreads, OpenMPNumThreadsClauseModifier NumThreadsModifier,
OpenMPSeverityClauseKind Severity, const Expr *Message) {
llvm_unreachable("Not supported in SIMD-only mode");
}

Expand Down Expand Up @@ -12138,9 +12152,10 @@ llvm::Value *CGOpenMPSIMDRuntime::emitForNext(CodeGenFunction &CGF,
llvm_unreachable("Not supported in SIMD-only mode");
}

void CGOpenMPSIMDRuntime::emitNumThreadsClause(CodeGenFunction &CGF,
llvm::Value *NumThreads,
SourceLocation Loc) {
void CGOpenMPSIMDRuntime::emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier, OpenMPSeverityClauseKind Severity,
const Expr *Message) {
llvm_unreachable("Not supported in SIMD-only mode");
}

Expand Down
54 changes: 44 additions & 10 deletions clang/lib/CodeGen/CGOpenMPRuntime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -777,11 +777,22 @@ class CGOpenMPRuntime {
/// specified, nullptr otherwise.
/// \param NumThreads The value corresponding to the num_threads clause, if
/// any, or nullptr.
/// \param NumThreadsModifier The modifier of the num_threads clause, if
/// any, ignored otherwise.
/// \param Severity The severity corresponding to the num_threads clause, if
/// any, ignored otherwise.
/// \param Message The message string corresponding to the num_threads clause,
/// if any, or nullptr.
///
virtual void emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond, llvm::Value *NumThreads);
virtual void
emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond,
llvm::Value *NumThreads,
OpenMPNumThreadsClauseModifier NumThreadsModifier =
OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr);

/// Emits a critical region.
/// \param CriticalName Name of the critical region.
Expand Down Expand Up @@ -1040,10 +1051,16 @@ class CGOpenMPRuntime {
/// Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
/// clause.
/// If the modifier 'strict' is given:
/// Emits call to void __kmpc_push_num_threads_strict(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads, int severity, const char *message) to
/// generate code for 'num_threads' clause with 'strict' modifier.
/// \param NumThreads An integer value of threads.
virtual void emitNumThreadsClause(CodeGenFunction &CGF,
llvm::Value *NumThreads,
SourceLocation Loc);
virtual void emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier = OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr);

/// Emit call to void __kmpc_push_proc_bind(ident_t *loc, kmp_int32
/// global_tid, int proc_bind) to generate code for 'proc_bind' clause.
Expand Down Expand Up @@ -1737,11 +1754,21 @@ class CGOpenMPSIMDRuntime final : public CGOpenMPRuntime {
/// specified, nullptr otherwise.
/// \param NumThreads The value corresponding to the num_threads clause, if
/// any, or nullptr.
/// \param NumThreadsModifier The modifier of the num_threads clause, if
/// any, ignored otherwise.
/// \param Severity The severity corresponding to the num_threads clause, if
/// any, ignored otherwise.
/// \param Message The message string corresponding to the num_threads clause,
/// if any, or nullptr.
///
void emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond, llvm::Value *NumThreads) override;
const Expr *IfCond, llvm::Value *NumThreads,
OpenMPNumThreadsClauseModifier NumThreadsModifier =
OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr) override;

/// Emits a critical region.
/// \param CriticalName Name of the critical region.
Expand Down Expand Up @@ -1911,9 +1938,16 @@ class CGOpenMPSIMDRuntime final : public CGOpenMPRuntime {
/// Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
/// clause.
/// If the modifier 'strict' is given:
/// Emits call to void __kmpc_push_num_threads_strict(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads, int severity, const char *message) to
/// generate code for 'num_threads' clause with 'strict' modifier.
/// \param NumThreads An integer value of threads.
void emitNumThreadsClause(CodeGenFunction &CGF, llvm::Value *NumThreads,
SourceLocation Loc) override;
void emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier = OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr) override;

/// Emit call to void __kmpc_push_proc_bind(ident_t *loc, kmp_int32
/// global_tid, int proc_bind) to generate code for 'proc_bind' clause.
Expand Down
61 changes: 35 additions & 26 deletions clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -899,9 +899,10 @@ void CGOpenMPRuntimeGPU::emitProcBindClause(CodeGenFunction &CGF,
// Nothing to do.
}

void CGOpenMPRuntimeGPU::emitNumThreadsClause(CodeGenFunction &CGF,
llvm::Value *NumThreads,
SourceLocation Loc) {
void CGOpenMPRuntimeGPU::emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier, OpenMPSeverityClauseKind Severity,
const Expr *Message) {
// Nothing to do.
}

Expand Down Expand Up @@ -1201,18 +1202,17 @@ void CGOpenMPRuntimeGPU::emitTeamsCall(CodeGenFunction &CGF,
emitOutlinedFunctionCall(CGF, Loc, OutlinedFn, OutlinedFnArgs);
}

void CGOpenMPRuntimeGPU::emitParallelCall(CodeGenFunction &CGF,
SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond,
llvm::Value *NumThreads) {
void CGOpenMPRuntimeGPU::emitParallelCall(
CodeGenFunction &CGF, SourceLocation Loc, llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars, const Expr *IfCond,
llvm::Value *NumThreads, OpenMPNumThreadsClauseModifier NumThreadsModifier,
OpenMPSeverityClauseKind Severity, const Expr *Message) {
if (!CGF.HaveInsertPoint())
return;

auto &&ParallelGen = [this, Loc, OutlinedFn, CapturedVars, IfCond,
NumThreads](CodeGenFunction &CGF,
PrePostActionTy &Action) {
auto &&ParallelGen = [this, Loc, OutlinedFn, CapturedVars, IfCond, NumThreads,
NumThreadsModifier, Severity, Message](
CodeGenFunction &CGF, PrePostActionTy &Action) {
CGBuilderTy &Bld = CGF.Builder;
llvm::Value *NumThreadsVal = NumThreads;
llvm::Function *WFn = WrapperFunctionsMap[OutlinedFn];
Expand Down Expand Up @@ -1260,21 +1260,30 @@ void CGOpenMPRuntimeGPU::emitParallelCall(CodeGenFunction &CGF,
NumThreadsVal = Bld.CreateZExtOrTrunc(NumThreadsVal, CGF.Int32Ty);

assert(IfCondVal && "Expected a value");
RuntimeFunction FnID = OMPRTL___kmpc_parallel_51;
llvm::Value *RTLoc = emitUpdateLocation(CGF, Loc);
llvm::Value *Args[] = {
RTLoc,
getThreadID(CGF, Loc),
IfCondVal,
NumThreadsVal,
llvm::ConstantInt::get(CGF.Int32Ty, -1),
FnPtr,
ID,
Bld.CreateBitOrPointerCast(CapturedVarsAddrs.emitRawPointer(CGF),
CGF.VoidPtrPtrTy),
llvm::ConstantInt::get(CGM.SizeTy, CapturedVars.size())};
CGF.EmitRuntimeCall(OMPBuilder.getOrCreateRuntimeFunction(
CGM.getModule(), OMPRTL___kmpc_parallel_51),
Args);
llvm::SmallVector<llvm::Value *, 10> Args(
{RTLoc, getThreadID(CGF, Loc), IfCondVal, NumThreadsVal,
llvm::ConstantInt::get(CGF.Int32Ty, -1), FnPtr, ID,
Bld.CreateBitOrPointerCast(CapturedVarsAddrs.emitRawPointer(CGF),
CGF.VoidPtrPtrTy),
llvm::ConstantInt::get(CGM.SizeTy, CapturedVars.size())});
if (NumThreadsModifier == OMPC_NUMTHREADS_strict) {
FnID = OMPRTL___kmpc_parallel_60;
// OpenMP 6.0, 10.4: "If no severity clause is specified then the effect
// is as if sev-level is fatal."
Args.append(
{llvm::ConstantInt::get(CGM.Int32Ty, true),
llvm::ConstantInt::get(CGM.Int32Ty,
Severity == OMPC_SEVERITY_warning ? 1 : 2)});
if (Message)
Args.push_back(CGF.EmitStringLiteralLValue(cast<StringLiteral>(Message))
.getPointer(CGF));
else
Args.push_back(llvm::ConstantPointerNull::get(CGF.VoidPtrTy));
}
CGF.EmitRuntimeCall(
OMPBuilder.getOrCreateRuntimeFunction(CGM.getModule(), FnID), Args);
};

RegionCodeGenTy RCG(ParallelGen);
Expand Down
26 changes: 21 additions & 5 deletions clang/lib/CodeGen/CGOpenMPRuntimeGPU.h
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -165,9 +165,16 @@ class CGOpenMPRuntimeGPU : public CGOpenMPRuntime {
/// Emits call to void __kmpc_push_num_threads(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads) to generate code for 'num_threads'
/// clause.
/// If the modifier 'strict' is given:
/// Emits call to void __kmpc_push_num_threads_strict(ident_t *loc, kmp_int32
/// global_tid, kmp_int32 num_threads, int severity, const char *message) to
/// generate code for 'num_threads' clause with 'strict' modifier.
/// \param NumThreads An integer value of threads.
void emitNumThreadsClause(CodeGenFunction &CGF, llvm::Value *NumThreads,
SourceLocation Loc) override;
void emitNumThreadsClause(
CodeGenFunction &CGF, llvm::Value *NumThreads, SourceLocation Loc,
OpenMPNumThreadsClauseModifier Modifier = OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr) override;

/// This function ought to emit, in the general case, a call to
// the openmp runtime kmpc_push_num_teams. In NVPTX backend it is not needed
Expand Down Expand Up @@ -229,12 +236,21 @@ class CGOpenMPRuntimeGPU : public CGOpenMPRuntime {
/// \param IfCond Condition in the associated 'if' clause, if it was
/// specified, nullptr otherwise.
/// \param NumThreads The value corresponding to the num_threads clause, if
/// any,
/// or nullptr.
/// any, or nullptr.
/// \param NumThreadsModifier The modifier of the num_threads clause, if
/// any, ignored otherwise.
/// \param Severity The severity corresponding to the num_threads clause, if
/// any, ignored otherwise.
/// \param Message The message string corresponding to the num_threads clause,
/// if any, or nullptr.
void emitParallelCall(CodeGenFunction &CGF, SourceLocation Loc,
llvm::Function *OutlinedFn,
ArrayRef<llvm::Value *> CapturedVars,
const Expr *IfCond, llvm::Value *NumThreads) override;
const Expr *IfCond, llvm::Value *NumThreads,
OpenMPNumThreadsClauseModifier NumThreadsModifier =
OMPC_NUMTHREADS_unknown,
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal,
const Expr *Message = nullptr) override;

/// Emit an implicit/explicit barrier for OpenMP threads.
/// \param Kind Directive for which this implicit barrier call must be
Expand Down
16 changes: 14 additions & 2 deletions clang/lib/CodeGen/CGStmtOpenMP.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1608,6 +1608,11 @@ static void emitCommonOMPParallelDirective(
const CodeGenBoundParametersTy &CodeGenBoundParameters) {
const CapturedStmt *CS = S.getCapturedStmt(OMPD_parallel);
llvm::Value *NumThreads = nullptr;
OpenMPNumThreadsClauseModifier Modifier = OMPC_NUMTHREADS_unknown;
// OpenMP 6.0, 10.4: "If no severity clause is specified then the effect is as
// if sev-level is fatal."
OpenMPSeverityClauseKind Severity = OMPC_SEVERITY_fatal;
clang::Expr *Message = nullptr;
llvm::Function *OutlinedFn =
CGF.CGM.getOpenMPRuntime().emitParallelOutlinedFunction(
CGF, S, *CS->getCapturedDecl()->param_begin(), InnermostKind,
Expand All @@ -1616,8 +1621,14 @@ static void emitCommonOMPParallelDirective(
CodeGenFunction::RunCleanupsScope NumThreadsScope(CGF);
NumThreads = CGF.EmitScalarExpr(NumThreadsClause->getNumThreads(),
/*IgnoreResultAssign=*/true);
Modifier = NumThreadsClause->getModifier();
if (const auto *MessageClause = S.getSingleClause<OMPMessageClause>())
Message = MessageClause->getMessageString();
if (const auto *SeverityClause = S.getSingleClause<OMPSeverityClause>())
Severity = SeverityClause->getSeverityKind();
CGF.CGM.getOpenMPRuntime().emitNumThreadsClause(
CGF, NumThreads, NumThreadsClause->getBeginLoc());
CGF, NumThreads, NumThreadsClause->getBeginLoc(), Modifier, Severity,
Message);
}
if (const auto *ProcBindClause = S.getSingleClause<OMPProcBindClause>()) {
CodeGenFunction::RunCleanupsScope ProcBindScope(CGF);
Expand All @@ -1642,7 +1653,8 @@ static void emitCommonOMPParallelDirective(
CodeGenBoundParameters(CGF, S, CapturedVars);
CGF.GenerateOpenMPCapturedVars(*CS, CapturedVars);
CGF.CGM.getOpenMPRuntime().emitParallelCall(CGF, S.getBeginLoc(), OutlinedFn,
CapturedVars, IfCond, NumThreads);
CapturedVars, IfCond, NumThreads,
Modifier, Severity, Message);
}

static bool isAllocatableDecl(const VarDecl *VD) {
Expand Down
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