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

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//===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements stmt-related attribute processing.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/ASTContext.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/StringExtras.h"
using namespace clang;
using namespace sema;
static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
FallThroughAttr Attr(S.Context, A);
if (isa<SwitchCase>(St)) {
S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
<< A << St->getBeginLoc();
SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
<< FixItHint::CreateInsertion(L, ";");
return nullptr;
}
auto *FnScope = S.getCurFunction();
if (FnScope->SwitchStack.empty()) {
S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
return nullptr;
}
// If this is spelled as the standard C++17 attribute, but not in C++17, warn
// about using it as an extension.
if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
!A.getScopeName())
S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A;
FnScope->setHasFallthroughStmt();
return ::new (S.Context) FallThroughAttr(S.Context, A);
}
static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
std::vector<StringRef> DiagnosticIdentifiers;
for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
StringRef RuleName;
if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
return nullptr;
// FIXME: Warn if the rule name is unknown. This is tricky because only
// clang-tidy knows about available rules.
DiagnosticIdentifiers.push_back(RuleName);
}
return ::new (S.Context) SuppressAttr(
S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size());
}
static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange) {
IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
IdentifierLoc *StateLoc = A.getArgAsIdent(2);
Expr *ValueExpr = A.getArgAsExpr(3);
StringRef PragmaName =
llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
.Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
PragmaNameLoc->Ident->getName())
.Default("clang loop");
// This could be handled automatically by adding a Subjects definition in
// Attr.td, but that would make the diagnostic behavior worse in this case
// because the user spells this attribute as a pragma.
if (!isa<DoStmt, ForStmt, CXXForRangeStmt, WhileStmt>(St)) {
std::string Pragma = "#pragma " + std::string(PragmaName);
S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
return nullptr;
}
LoopHintAttr::OptionType Option;
LoopHintAttr::LoopHintState State;
auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
LoopHintAttr::LoopHintState S) {
Option = O;
State = S;
};
if (PragmaName == "nounroll") {
SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
} else if (PragmaName == "unroll") {
// #pragma unroll N
if (ValueExpr)
SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
else
SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
} else if (PragmaName == "nounroll_and_jam") {
SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
} else if (PragmaName == "unroll_and_jam") {
// #pragma unroll_and_jam N
if (ValueExpr)
SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
else
SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
} else {
// #pragma clang loop ...
assert(OptionLoc && OptionLoc->Ident &&
"Attribute must have valid option info.");
Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
OptionLoc->Ident->getName())
.Case("vectorize", LoopHintAttr::Vectorize)
.Case("vectorize_width", LoopHintAttr::VectorizeWidth)
.Case("interleave", LoopHintAttr::Interleave)
.Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
.Case("interleave_count", LoopHintAttr::InterleaveCount)
.Case("unroll", LoopHintAttr::Unroll)
.Case("unroll_count", LoopHintAttr::UnrollCount)
.Case("pipeline", LoopHintAttr::PipelineDisabled)
.Case("pipeline_initiation_interval",
LoopHintAttr::PipelineInitiationInterval)
.Case("distribute", LoopHintAttr::Distribute)
.Default(LoopHintAttr::Vectorize);
if (Option == LoopHintAttr::VectorizeWidth) {
assert((ValueExpr || (StateLoc && StateLoc->Ident)) &&
"Attribute must have a valid value expression or argument.");
if (ValueExpr && S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
return nullptr;
if (StateLoc && StateLoc->Ident && StateLoc->Ident->isStr("scalable"))
State = LoopHintAttr::ScalableWidth;
else
State = LoopHintAttr::FixedWidth;
} else if (Option == LoopHintAttr::InterleaveCount ||
Option == LoopHintAttr::UnrollCount ||
Option == LoopHintAttr::PipelineInitiationInterval) {
assert(ValueExpr && "Attribute must have a valid value expression.");
if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
return nullptr;
State = LoopHintAttr::Numeric;
} else if (Option == LoopHintAttr::Vectorize ||
Option == LoopHintAttr::Interleave ||
Option == LoopHintAttr::VectorizePredicate ||
Option == LoopHintAttr::Unroll ||
Option == LoopHintAttr::Distribute ||
Option == LoopHintAttr::PipelineDisabled) {
assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
if (StateLoc->Ident->isStr("disable"))
State = LoopHintAttr::Disable;
else if (StateLoc->Ident->isStr("assume_safety"))
State = LoopHintAttr::AssumeSafety;
else if (StateLoc->Ident->isStr("full"))
State = LoopHintAttr::Full;
else if (StateLoc->Ident->isStr("enable"))
State = LoopHintAttr::Enable;
else
llvm_unreachable("bad loop hint argument");
} else
llvm_unreachable("bad loop hint");
}
return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
}
namespace {
class CallExprFinder : public ConstEvaluatedExprVisitor<CallExprFinder> {
bool FoundAsmStmt = false;
std::vector<const CallExpr *> CallExprs;
public:
typedef ConstEvaluatedExprVisitor<CallExprFinder> Inherited;
CallExprFinder(Sema &S, const Stmt *St) : Inherited(S.Context) { Visit(St); }
bool foundCallExpr() { return !CallExprs.empty(); }
const std::vector<const CallExpr *> &getCallExprs() { return CallExprs; }
bool foundAsmStmt() { return FoundAsmStmt; }
void VisitCallExpr(const CallExpr *E) { CallExprs.push_back(E); }
void VisitAsmStmt(const AsmStmt *S) { FoundAsmStmt = true; }
void Visit(const Stmt *St) {
if (!St)
return;
ConstEvaluatedExprVisitor<CallExprFinder>::Visit(St);
}
};
} // namespace
static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
NoMergeAttr NMA(S.Context, A);
CallExprFinder CEF(S, St);
if (!CEF.foundCallExpr() && !CEF.foundAsmStmt()) {
S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt)
<< A;
return nullptr;
}
return ::new (S.Context) NoMergeAttr(S.Context, A);
}
static Attr *handleNoInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
NoInlineAttr NIA(S.Context, A);
if (!NIA.isClangNoInline()) {
S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
<< "[[clang::noinline]]";
return nullptr;
}
CallExprFinder CEF(S, St);
if (!CEF.foundCallExpr()) {
S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt)
<< A;
return nullptr;
}
for (const auto *CallExpr : CEF.getCallExprs()) {
const Decl *Decl = CallExpr->getCalleeDecl();
if (Decl->hasAttr<AlwaysInlineAttr>() || Decl->hasAttr<FlattenAttr>())
S.Diag(St->getBeginLoc(), diag::warn_function_stmt_attribute_precedence)
<< A << (Decl->hasAttr<AlwaysInlineAttr>() ? 0 : 1);
}
return ::new (S.Context) NoInlineAttr(S.Context, A);
}
static Attr *handleAlwaysInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
AlwaysInlineAttr AIA(S.Context, A);
if (!AIA.isClangAlwaysInline()) {
S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
<< "[[clang::always_inline]]";
return nullptr;
}
CallExprFinder CEF(S, St);
if (!CEF.foundCallExpr()) {
S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt)
<< A;
return nullptr;
}
for (const auto *CallExpr : CEF.getCallExprs()) {
const Decl *Decl = CallExpr->getCalleeDecl();
if (Decl->hasAttr<NoInlineAttr>() || Decl->hasAttr<FlattenAttr>())
S.Diag(St->getBeginLoc(), diag::warn_function_stmt_attribute_precedence)
<< A << (Decl->hasAttr<NoInlineAttr>() ? 2 : 1);
}
return ::new (S.Context) AlwaysInlineAttr(S.Context, A);
}
static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
// Validation is in Sema::ActOnAttributedStmt().
return ::new (S.Context) MustTailAttr(S.Context, A);
}
static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
return ::new (S.Context) LikelyAttr(S.Context, A);
}
static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
return ::new (S.Context) UnlikelyAttr(S.Context, A);
}
#define WANT_STMT_MERGE_LOGIC
#include "clang/Sema/AttrParsedAttrImpl.inc"
#undef WANT_STMT_MERGE_LOGIC
static void
CheckForIncompatibleAttributes(Sema &S,
const SmallVectorImpl<const Attr *> &Attrs) {
// The vast majority of attributed statements will only have one attribute
// on them, so skip all of the checking in the common case.
if (Attrs.size() < 2)
return;
// First, check for the easy cases that are table-generated for us.
if (!DiagnoseMutualExclusions(S, Attrs))
return;
// There are 6 categories of loop hints attributes: vectorize, interleave,
// unroll, unroll_and_jam, pipeline and distribute. Except for distribute they
// come in two variants: a state form and a numeric form. The state form
// selectively defaults/enables/disables the transformation for the loop
// (for unroll, default indicates full unrolling rather than enabling the
// transformation). The numeric form form provides an integer hint (for
// example, unroll count) to the transformer. The following array accumulates
// the hints encountered while iterating through the attributes to check for
// compatibility.
struct {
const LoopHintAttr *StateAttr;
const LoopHintAttr *NumericAttr;
} HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
{nullptr, nullptr}};
for (const auto *I : Attrs) {
const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
// Skip non loop hint attributes
if (!LH)
continue;
LoopHintAttr::OptionType Option = LH->getOption();
enum {
Vectorize,
Interleave,
Unroll,
UnrollAndJam,
Distribute,
Pipeline,
VectorizePredicate
} Category;
switch (Option) {
case LoopHintAttr::Vectorize:
case LoopHintAttr::VectorizeWidth:
Category = Vectorize;
break;
case LoopHintAttr::Interleave:
case LoopHintAttr::InterleaveCount:
Category = Interleave;
break;
case LoopHintAttr::Unroll:
case LoopHintAttr::UnrollCount:
Category = Unroll;
break;
case LoopHintAttr::UnrollAndJam:
case LoopHintAttr::UnrollAndJamCount:
Category = UnrollAndJam;
break;
case LoopHintAttr::Distribute:
// Perform the check for duplicated 'distribute' hints.
Category = Distribute;
break;
case LoopHintAttr::PipelineDisabled:
case LoopHintAttr::PipelineInitiationInterval:
Category = Pipeline;
break;
case LoopHintAttr::VectorizePredicate:
Category = VectorizePredicate;
break;
};
assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
auto &CategoryState = HintAttrs[Category];
const LoopHintAttr *PrevAttr;
if (Option == LoopHintAttr::Vectorize ||
Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
Option == LoopHintAttr::UnrollAndJam ||
Option == LoopHintAttr::VectorizePredicate ||
Option == LoopHintAttr::PipelineDisabled ||
Option == LoopHintAttr::Distribute) {
// Enable|Disable|AssumeSafety hint. For example, vectorize(enable).
PrevAttr = CategoryState.StateAttr;
CategoryState.StateAttr = LH;
} else {
// Numeric hint. For example, vectorize_width(8).
PrevAttr = CategoryState.NumericAttr;
CategoryState.NumericAttr = LH;
}
PrintingPolicy Policy(S.Context.getLangOpts());
SourceLocation OptionLoc = LH->getRange().getBegin();
if (PrevAttr)
// Cannot specify same type of attribute twice.
S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
<< /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
<< LH->getDiagnosticName(Policy);
if (CategoryState.StateAttr && CategoryState.NumericAttr &&
(Category == Unroll || Category == UnrollAndJam ||
CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
// Disable hints are not compatible with numeric hints of the same
// category. As a special case, numeric unroll hints are also not
// compatible with enable or full form of the unroll pragma because these
// directives indicate full unrolling.
S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
<< /*Duplicate=*/false
<< CategoryState.StateAttr->getDiagnosticName(Policy)
<< CategoryState.NumericAttr->getDiagnosticName(Policy);
}
}
}
static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
// Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
// useful for OpenCL 1.x too and doesn't require HW support.
// opencl_unroll_hint can have 0 arguments (compiler
// determines unrolling factor) or 1 argument (the unroll factor provided
// by the user).
unsigned UnrollFactor = 0;
if (A.getNumArgs() == 1) {
Expr *E = A.getArgAsExpr(0);
Optional<llvm::APSInt> ArgVal;
if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) {
S.Diag(A.getLoc(), diag::err_attribute_argument_type)
<< A << AANT_ArgumentIntegerConstant << E->getSourceRange();
return nullptr;
}
int Val = ArgVal->getSExtValue();
if (Val <= 0) {
S.Diag(A.getRange().getBegin(),
diag::err_attribute_requires_positive_integer)
<< A << /* positive */ 0;
return nullptr;
}
UnrollFactor = static_cast<unsigned>(Val);
}
return ::new (S.Context) OpenCLUnrollHintAttr(S.Context, A, UnrollFactor);
}
static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
SourceRange Range) {
if (A.isInvalid() || A.getKind() == ParsedAttr::IgnoredAttribute)
return nullptr;
// Unknown attributes are automatically warned on. Target-specific attributes
// which do not apply to the current target architecture are treated as
// though they were unknown attributes.
const TargetInfo *Aux = S.Context.getAuxTargetInfo();
if (A.getKind() == ParsedAttr::UnknownAttribute ||
!(A.existsInTarget(S.Context.getTargetInfo()) ||
(S.Context.getLangOpts().SYCLIsDevice && Aux &&
A.existsInTarget(*Aux)))) {
S.Diag(A.getLoc(), A.isDeclspecAttribute()
? (unsigned)diag::warn_unhandled_ms_attribute_ignored
: (unsigned)diag::warn_unknown_attribute_ignored)
<< A << A.getRange();
return nullptr;
}
if (S.checkCommonAttributeFeatures(St, A))
return nullptr;
switch (A.getKind()) {
case ParsedAttr::AT_AlwaysInline:
return handleAlwaysInlineAttr(S, St, A, Range);
case ParsedAttr::AT_FallThrough:
return handleFallThroughAttr(S, St, A, Range);
case ParsedAttr::AT_LoopHint:
return handleLoopHintAttr(S, St, A, Range);
case ParsedAttr::AT_OpenCLUnrollHint:
return handleOpenCLUnrollHint(S, St, A, Range);
case ParsedAttr::AT_Suppress:
return handleSuppressAttr(S, St, A, Range);
case ParsedAttr::AT_NoMerge:
return handleNoMergeAttr(S, St, A, Range);
case ParsedAttr::AT_NoInline:
return handleNoInlineAttr(S, St, A, Range);
case ParsedAttr::AT_MustTail:
return handleMustTailAttr(S, St, A, Range);
case ParsedAttr::AT_Likely:
return handleLikely(S, St, A, Range);
case ParsedAttr::AT_Unlikely:
return handleUnlikely(S, St, A, Range);
default:
// N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a
// declaration attribute is not written on a statement, but this code is
// needed for attributes in Attr.td that do not list any subjects.
S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
<< A << St->getBeginLoc();
return nullptr;
}
}
void Sema::ProcessStmtAttributes(Stmt *S, const ParsedAttributes &InAttrs,
SmallVectorImpl<const Attr *> &OutAttrs) {
for (const ParsedAttr &AL : InAttrs) {
if (const Attr *A = ProcessStmtAttribute(*this, S, AL, InAttrs.Range))
OutAttrs.push_back(A);
}
CheckForIncompatibleAttributes(*this, OutAttrs);
}
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