[clang] Always register `asm` attribute first in a Decl. (PR #162687)
Giuliano Belinassi via cfe-commits
cfe-commits at lists.llvm.org
Fri Oct 17 17:19:47 PDT 2025
https://github.com/giulianobelinassi updated https://github.com/llvm/llvm-project/pull/162687
>From bf45304d48bf15dbf3ea8064caf1966dc4a72bc3 Mon Sep 17 00:00:00 2001
From: Giuliano Belinassi <gbelinassi at suse.de>
Date: Thu, 9 Oct 2025 13:01:44 -0300
Subject: [PATCH] Always register `asm` attribute first in a Decl.
Previously, clang's SemaDecl processed `asm` attributes after every
other attribute in the Decl, unlike gcc and clang's own parser which
requires `asm` attributes to be the first one in the declaration
(see #162556). Therefore, move the processing of `asm` attributes
to be the first one in the attributes list.
Signed-off-by: Giuliano Belinassi <gbelinassi at suse.de>
---
clang/docs/ReleaseNotes.rst | 11 +++
clang/include/clang/Sema/Sema.h | 7 ++
clang/lib/Sema/SemaDecl.cpp | 136 ++++++++++++++++++--------------
clang/test/Sema/attr-print.c | 3 +
4 files changed, 98 insertions(+), 59 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 5e9a71e1e74d6..4d7b2b071b6f8 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -128,6 +128,17 @@ AST Dumping Potentially Breaking Changes
- Default arguments of template template parameters are pretty-printed now.
+- Pretty-printing of ``asm`` attributes are now always the first attribute
+ on the right side of the declaration. Before we had, e.g.:
+
+ ``__attribute__(("visibility")) asm("string")``
+
+ Now we have:
+
+ ``asm("string") __attribute__(("visibility"))``
+
+ Which is accepted by both clang and gcc parsers.
+
Clang Frontend Potentially Breaking Changes
-------------------------------------------
- Members of anonymous unions/structs are now injected as ``IndirectFieldDecl``
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 265462a86e405..0ae17022b54b3 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3961,6 +3961,13 @@ class Sema final : public SemaBase {
bool &AddToScope,
ArrayRef<BindingDecl *> Bindings = {});
+private:
+ // Perform a check on an AsmLabel to verify its consistency and emit
+ // diagnostics in case of an error.
+ void CheckAsmLabel(Scope *S, Expr *AsmLabelExpr, StorageClass SC,
+ TypeSourceInfo *TInfo, VarDecl *);
+
+public:
/// Perform semantic checking on a newly-created variable
/// declaration.
///
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6eaf7b9435491..ac70158c391c8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7640,6 +7640,58 @@ static bool isMainVar(DeclarationName Name, VarDecl *VD) {
VD->isExternC());
}
+void Sema::CheckAsmLabel(Scope *S, Expr *E, StorageClass SC,
+ TypeSourceInfo *TInfo, VarDecl *NewVD) {
+
+ // Quickly return if the function does not have an `asm` attribute.
+ if (E == nullptr)
+ return;
+
+ // The parser guarantees this is a string.
+ StringLiteral *SE = cast<StringLiteral>(E);
+ StringRef Label = SE->getString();
+ QualType R = TInfo->getType();
+ if (S->getFnParent() != nullptr) {
+ switch (SC) {
+ case SC_None:
+ case SC_Auto:
+ Diag(E->getExprLoc(), diag::warn_asm_label_on_auto_decl) << Label;
+ break;
+ case SC_Register:
+ // Local Named register
+ if (!Context.getTargetInfo().isValidGCCRegisterName(Label) &&
+ DeclAttrsMatchCUDAMode(getLangOpts(), getCurFunctionDecl()))
+ Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
+ break;
+ case SC_Static:
+ case SC_Extern:
+ case SC_PrivateExtern:
+ break;
+ }
+ } else if (SC == SC_Register) {
+ // Global Named register
+ if (DeclAttrsMatchCUDAMode(getLangOpts(), NewVD)) {
+ const auto &TI = Context.getTargetInfo();
+ bool HasSizeMismatch;
+
+ if (!TI.isValidGCCRegisterName(Label))
+ Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
+ else if (!TI.validateGlobalRegisterVariable(Label, Context.getTypeSize(R),
+ HasSizeMismatch))
+ Diag(E->getExprLoc(), diag::err_asm_invalid_global_var_reg) << Label;
+ else if (HasSizeMismatch)
+ Diag(E->getExprLoc(), diag::err_asm_register_size_mismatch) << Label;
+ }
+
+ if (!R->isIntegralType(Context) && !R->isPointerType()) {
+ Diag(TInfo->getTypeLoc().getBeginLoc(),
+ diag::err_asm_unsupported_register_type)
+ << TInfo->getTypeLoc().getSourceRange();
+ NewVD->setInvalidDecl(true);
+ }
+ }
+}
+
NamedDecl *Sema::ActOnVariableDeclarator(
Scope *S, Declarator &D, DeclContext *DC, TypeSourceInfo *TInfo,
LookupResult &Previous, MultiTemplateParamsArg TemplateParamLists,
@@ -8124,6 +8176,26 @@ NamedDecl *Sema::ActOnVariableDeclarator(
}
}
+ if (Expr *E = D.getAsmLabel()) {
+ // The parser guarantees this is a string.
+ StringLiteral *SE = cast<StringLiteral>(E);
+ StringRef Label = SE->getString();
+
+ // Insert the asm attribute.
+ NewVD->addAttr(AsmLabelAttr::Create(Context, Label, SE->getStrTokenLoc(0)));
+ } else if (!ExtnameUndeclaredIdentifiers.empty()) {
+ llvm::DenseMap<IdentifierInfo *, AsmLabelAttr *>::iterator I =
+ ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
+ if (I != ExtnameUndeclaredIdentifiers.end()) {
+ if (isDeclExternC(NewVD)) {
+ NewVD->addAttr(I->second);
+ ExtnameUndeclaredIdentifiers.erase(I);
+ } else
+ Diag(NewVD->getLocation(), diag::warn_redefine_extname_not_applied)
+ << /*Variable*/ 1 << NewVD;
+ }
+ }
+
// Handle attributes prior to checking for duplicates in MergeVarDecl
ProcessDeclAttributes(S, NewVD, D);
@@ -8174,65 +8246,11 @@ NamedDecl *Sema::ActOnVariableDeclarator(
if (getLangOpts().ObjCAutoRefCount && ObjC().inferObjCARCLifetime(NewVD))
NewVD->setInvalidDecl();
- // Handle GNU asm-label extension (encoded as an attribute).
- if (Expr *E = D.getAsmLabel()) {
- // The parser guarantees this is a string.
- StringLiteral *SE = cast<StringLiteral>(E);
- StringRef Label = SE->getString();
- if (S->getFnParent() != nullptr) {
- switch (SC) {
- case SC_None:
- case SC_Auto:
- Diag(E->getExprLoc(), diag::warn_asm_label_on_auto_decl) << Label;
- break;
- case SC_Register:
- // Local Named register
- if (!Context.getTargetInfo().isValidGCCRegisterName(Label) &&
- DeclAttrsMatchCUDAMode(getLangOpts(), getCurFunctionDecl()))
- Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
- break;
- case SC_Static:
- case SC_Extern:
- case SC_PrivateExtern:
- break;
- }
- } else if (SC == SC_Register) {
- // Global Named register
- if (DeclAttrsMatchCUDAMode(getLangOpts(), NewVD)) {
- const auto &TI = Context.getTargetInfo();
- bool HasSizeMismatch;
-
- if (!TI.isValidGCCRegisterName(Label))
- Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
- else if (!TI.validateGlobalRegisterVariable(Label,
- Context.getTypeSize(R),
- HasSizeMismatch))
- Diag(E->getExprLoc(), diag::err_asm_invalid_global_var_reg) << Label;
- else if (HasSizeMismatch)
- Diag(E->getExprLoc(), diag::err_asm_register_size_mismatch) << Label;
- }
-
- if (!R->isIntegralType(Context) && !R->isPointerType()) {
- Diag(TInfo->getTypeLoc().getBeginLoc(),
- diag::err_asm_unsupported_register_type)
- << TInfo->getTypeLoc().getSourceRange();
- NewVD->setInvalidDecl(true);
- }
- }
-
- NewVD->addAttr(AsmLabelAttr::Create(Context, Label, SE->getStrTokenLoc(0)));
- } else if (!ExtnameUndeclaredIdentifiers.empty()) {
- llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
- ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
- if (I != ExtnameUndeclaredIdentifiers.end()) {
- if (isDeclExternC(NewVD)) {
- NewVD->addAttr(I->second);
- ExtnameUndeclaredIdentifiers.erase(I);
- } else
- Diag(NewVD->getLocation(), diag::warn_redefine_extname_not_applied)
- << /*Variable*/1 << NewVD;
- }
- }
+ // Check the ASM label here, as we need to know all other attributes of the
+ // Decl first. Otherwise, we can't know if the asm label refers to the
+ // host or device in a CUDA context. The device has other registers than
+ // host and we must know where the function will be placed.
+ CheckAsmLabel(S, D.getAsmLabel(), SC, TInfo, NewVD);
// Find the shadowed declaration before filtering for scope.
NamedDecl *ShadowedDecl = D.getCXXScopeSpec().isEmpty()
diff --git a/clang/test/Sema/attr-print.c b/clang/test/Sema/attr-print.c
index 8492356e5d2e5..211e61a937f63 100644
--- a/clang/test/Sema/attr-print.c
+++ b/clang/test/Sema/attr-print.c
@@ -35,3 +35,6 @@ int * __sptr * __ptr32 ppsp32;
// CHECK: __attribute__((availability(macos, strict, introduced=10.6)));
void f6(int) __attribute__((availability(macosx,strict,introduced=10.6)));
+
+// CHECK: _libc_intl_domainname asm("__gi__libc_intl_domainname") __attribute__((visibility("hidden")));
+extern const char _libc_intl_domainname[]; extern typeof (_libc_intl_domainname) _libc_intl_domainname asm("__gi__libc_intl_domainname") __attribute__((visibility("hidden")));
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