[clang] 6a2d309 - [Clang] Diagnose conflict between always_inline/noinline attributes (#215173)
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cfe-commits at lists.llvm.org
Sun Aug 16 09:16:07 PDT 2026
Author: Kenzo Tjandra
Date: 2026-08-16T16:16:01Z
New Revision: 6a2d309c7d204730a9a35f3261f8448efeb6c5e3
URL: https://github.com/llvm/llvm-project/commit/6a2d309c7d204730a9a35f3261f8448efeb6c5e3
DIFF: https://github.com/llvm/llvm-project/commit/6a2d309c7d204730a9a35f3261f8448efeb6c5e3.diff
LOG: [Clang] Diagnose conflict between always_inline/noinline attributes (#215173)
This PR aims to diagnose `always_inline` and `noinline` conflicts which
currently could pass silently through `Sema` or cause a crash (with
assertions enabled). Changes include:
- Added `MutualExclusions<[AlwaysInline, NoInline]>` in `Attr.td`
- Prevent `always_inline` and `noinline` from being propagated from
generic to specialized templates in `SemaDecl.cpp`
- Prevent inner attributes from clobbering unrelated outer attributes
(e.g. `noinline` and `nomerge`) in both `CGStmt.cpp` and
`CIRGenStmt.cpp`
Something to consider though: Should we prevent propagating conflicting
attributes when doing explicit template specializations in general, not
just `inline`, e.g. `hot`/`cold`, `convergent`/`noconvergent`, etc.
Fixes #214764
---------
Co-authored-by: Erich Keane <ekeane at nvidia.com>
Added:
clang/test/CodeGen/attr-noinline-always-inline.cpp
Modified:
clang/include/clang/Basic/Attr.td
clang/lib/CIR/CodeGen/CIRGenStmt.cpp
clang/lib/CodeGen/CGStmt.cpp
clang/lib/Sema/SemaDecl.cpp
clang/test/CIR/CodeGen/callsite-inline-attributes.cpp
clang/test/CodeGenHLSL/HLSLControlFlowHint.hlsl
clang/test/Sema/attr-noinline.cpp
Removed:
################################################################################
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index f599e6fecc8ff..252b53e25e5c8 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -2420,6 +2420,8 @@ def NoInline : DeclOrStmtAttr {
let SimpleHandler = 1;
}
+def : MutualExclusions<[AlwaysInline, NoInline]>;
+
def NoOutline : DeclOrStmtAttr {
let Spellings = [Clang<"no_outline">];
let Subjects = SubjectList<[Function, ObjCMethod, Block], ErrorDiag>;
diff --git a/clang/lib/CIR/CodeGen/CIRGenStmt.cpp b/clang/lib/CIR/CodeGen/CIRGenStmt.cpp
index 39919cc28981a..28c82794614d5 100644
--- a/clang/lib/CIR/CodeGen/CIRGenStmt.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenStmt.cpp
@@ -90,9 +90,9 @@ mlir::LogicalResult CIRGenFunction::emitCompoundStmtWithoutScope(
mlir::LogicalResult
CIRGenFunction::emitAttributedStmt(const AttributedStmt &s) {
- bool noinline = false;
- bool alwaysinline = false;
- const CallExpr *musttail = nullptr;
+ bool noinline = inNoInlineAttributedStmt;
+ bool alwaysinline = inAlwaysInlineAttributedStmt;
+ const CallExpr *musttail = mustTailCall;
for (const Attr *attr : s.getAttrs()) {
switch (attr->getKind()) {
@@ -108,9 +108,11 @@ CIRGenFunction::emitAttributedStmt(const AttributedStmt &s) {
break;
case attr::NoInline:
noinline = true;
+ alwaysinline = false;
break;
case attr::AlwaysInline:
alwaysinline = true;
+ noinline = false;
break;
case attr::MustTail: {
const Stmt *sub = s.getSubStmt();
@@ -131,6 +133,9 @@ CIRGenFunction::emitAttributedStmt(const AttributedStmt &s) {
}
}
+ assert(!(alwaysinline && noinline) &&
+ "alwaysinline and noinline are mutually exclusive");
+
SaveAndRestore save_noinline(inNoInlineAttributedStmt, noinline);
SaveAndRestore save_alwaysinline(inAlwaysInlineAttributedStmt, alwaysinline);
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 18f1e87d3245d..bf6e6eb50f555 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -782,14 +782,13 @@ void CodeGenFunction::EmitLabelStmt(const LabelStmt &S) {
}
void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
- bool nomerge = false;
- bool noinline = false;
- bool alwaysinline = false;
- bool noconvergent = false;
- StringRef amdgpuAVMode;
- HLSLControlFlowHintAttr::Spelling flattenOrBranch =
- HLSLControlFlowHintAttr::SpellingNotCalculated;
- const CallExpr *musttail = nullptr;
+ bool nomerge = InNoMergeAttributedStmt;
+ bool noinline = InNoInlineAttributedStmt;
+ bool alwaysinline = InAlwaysInlineAttributedStmt;
+ bool noconvergent = InNoConvergentAttributedStmt;
+ StringRef amdgpuAVMode = AMDGPUAvailableVisibleMode;
+ HLSLControlFlowHintAttr::Spelling flattenOrBranch = HLSLControlFlowAttr;
+ const CallExpr *musttail = MustTailCall;
const AtomicAttr *AA = nullptr;
for (const auto *A : S.getAttrs()) {
@@ -801,9 +800,11 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
break;
case attr::NoInline:
noinline = true;
+ alwaysinline = false;
break;
case attr::AlwaysInline:
alwaysinline = true;
+ noinline = false;
break;
case attr::NoConvergent:
noconvergent = true;
@@ -832,6 +833,10 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
} break;
}
}
+
+ assert(!(alwaysinline && noinline) &&
+ "alwaysinline and noinline are mutually exclusive");
+
SaveAndRestore save_nomerge(InNoMergeAttributedStmt, nomerge);
SaveAndRestore save_noinline(InNoInlineAttributedStmt, noinline);
SaveAndRestore save_alwaysinline(InAlwaysInlineAttributedStmt, alwaysinline);
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index d87710d3cf140..a65596d5bbeeb 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3389,11 +3389,14 @@ void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
if (isa<UsedAttr>(I) || isa<RetainAttr>(I))
continue;
- if (isa<InferredNoReturnAttr>(I)) {
+ // Don't propagate inferred noreturn or conflicting inline attributes to
+ // explicit specializations.
+ if (isa<InferredNoReturnAttr>(I) || isa<AlwaysInlineAttr>(I) ||
+ isa<NoInlineAttr>(I)) {
if (auto *FD = dyn_cast<FunctionDecl>(New);
FD &&
FD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization)
- continue; // Don't propagate inferred noreturn attributes to explicit
+ continue;
}
if (mergeDeclAttribute(*this, New, I, LocalAMK))
diff --git a/clang/test/CIR/CodeGen/callsite-inline-attributes.cpp b/clang/test/CIR/CodeGen/callsite-inline-attributes.cpp
index 13a4fcfbb690c..d9916e725ca50 100644
--- a/clang/test/CIR/CodeGen/callsite-inline-attributes.cpp
+++ b/clang/test/CIR/CodeGen/callsite-inline-attributes.cpp
@@ -49,6 +49,14 @@ void caller() {
// CIR: cir.call %{{.*}}() {inline_kind = #cir.inline_kind<no_inline>}
// LLVM: call void %{{.*}}() #[[NOINLINE]]
}
+
+ [[clang::noinline]]
+ {
+ [[clang::always_inline]]
+ callee();
+ // CIR: cir.call @_Z6calleev() {inline_kind = #cir.inline_kind<always_inline>}
+ // LLVM: call void @_Z6calleev() #[[ALWAYSINLINE]]
+ }
}
// LLVM: attributes #[[ALWAYSINLINE]] = { alwaysinline }
diff --git a/clang/test/CodeGen/attr-noinline-always-inline.cpp b/clang/test/CodeGen/attr-noinline-always-inline.cpp
new file mode 100644
index 0000000000000..ee7fa86a85dd7
--- /dev/null
+++ b/clang/test/CodeGen/attr-noinline-always-inline.cpp
@@ -0,0 +1,92 @@
+// RUN: %clang_cc1 -O1 -disable-llvm-passes -triple x86_64-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+template <typename T>
+[[clang::noinline]] void foo(T) {}
+
+// Explicit specializations should not inherit noinline
+template <>
+[[clang::always_inline]] void foo<int>(int) {}
+
+template <>
+void foo<long>(long) {}
+
+void caller() {
+ foo<float>(4.2f); // expect noinline on function
+ foo<int>(42); // expect alwaysinline on function
+ foo<long>(42L); // expect no noinline attribute
+}
+// CHECK: define {{.*}}void @_Z3fooIiEvT_({{.*}}) #[[ALWAYSINLINE:[0-9]+]]
+// CHECK: define {{.*}}void @_Z3fooIlEvT_({{.*}}) #[[BARE:[0-9]+]]
+// CHECK: define {{.*}}void @_Z3fooIfEvT_({{.*}}) #[[NOINLINE:[0-9]+]]
+
+// Inner function should not clobber non-conflicting attributes
+void inner_fn();
+
+void outer_fn() {
+ [[clang::noinline]]
+ {
+ [[clang::nomerge]] // unrelated to inlining
+ inner_fn();
+ }
+}
+// CHECK: call void @_Z8inner_fnv() #[[NOINLINE_NOMERGE:[0-9]+]]
+
+void inner_fn2();
+
+void outer_fn2() {
+ [[clang::nomerge]]
+ {
+ [[clang::noinline]] // unrelated to nomerge
+ inner_fn2();
+ }
+}
+// CHECK: call void @_Z9inner_fn2v() #[[NOINLINE_NOMERGE]]
+
+[[clang::convergent]]
+void inner_fn3();
+
+void outer_fn3() {
+ [[clang::always_inline]]
+ {
+ [[clang::noconvergent]] // unrelated to inlining
+ inner_fn3();
+ }
+}
+// CHECK: call void @_Z9inner_fn3v() #[[ALWAYSINLINE_ONLY:[0-9]+]]
+
+[[clang::convergent]]
+void inner_fn4();
+
+void outer_fn4() {
+ [[clang::noconvergent]]
+ {
+ [[clang::always_inline]] // unrelated to noconvergent
+ inner_fn4();
+ }
+}
+// CHECK: call void @_Z9inner_fn4v() #[[ALWAYSINLINE_ONLY]]
+
+// Inner function should clobber a conflicting attribute
+void inner_fn5();
+
+void outer_fn5() {
+ [[clang::noinline]]
+ {
+ [[clang::always_inline]]
+ inner_fn5();
+ }
+}
+// CHECK: call void @_Z9inner_fn5v() #[[ALWAYSINLINE_ONLY]]
+
+// CHECK: attributes #[[ALWAYSINLINE]] = {
+// CHECK-SAME: alwaysinline
+// CHECK-NOT: noinline
+// CHECK: attributes #[[BARE]] = {
+// CHECK-NOT: alwaysinline
+// CHECK-NOT: noinline
+// CHECK: attributes #[[NOINLINE]] = {
+// CHECK-SAME: noinline
+// CHECK-NOT: alwaysinline
+
+// CHECK: attributes #[[NOINLINE_NOMERGE]] = { noinline nomerge }
+// CHECK: attributes #[[ALWAYSINLINE_ONLY]] = { alwaysinline }
diff --git a/clang/test/CodeGenHLSL/HLSLControlFlowHint.hlsl b/clang/test/CodeGenHLSL/HLSLControlFlowHint.hlsl
index 6737cd3ee78ba..09ae698d3d8c0 100644
--- a/clang/test/CodeGenHLSL/HLSLControlFlowHint.hlsl
+++ b/clang/test/CodeGenHLSL/HLSLControlFlowHint.hlsl
@@ -44,5 +44,27 @@ export int test_no_attr(int X){
return resp;
}
+// CHECK-LABEL: test_nested_branch_preserved
+// CHECK: br i1 %{{.*}}, label %if.then, label %if.end{{.*}}, !hlsl.controlflow.hint [[HINT_BRANCH]]
+// CHECK: br i1 %{{.*}}, label %if.then{{.*}}, label %if.end{{.*}}, !hlsl.controlflow.hint [[HINT_BRANCH]]
+void foo(int);
+export void test_nested_branch_preserved(int X, int Y) {
+ [branch] if (X) {
+ [[clang::noinline]] // unrelated to branch
+ if (Y) foo(Y);
+ }
+}
+
+// CHECK-LABEL: test_nested_flatten_preserved
+// CHECK: br i1 %{{.*}}, label %if.then, label %if.end{{.*}}, !hlsl.controlflow.hint [[HINT_FLATTEN]]
+// CHECK: br i1 %{{.*}}, label %if.then{{.*}}, label %if.end{{.*}}, !hlsl.controlflow.hint [[HINT_FLATTEN]]
+void bar(int);
+export void test_nested_flatten_preserved(int X, int Y) {
+ [flatten] if (X) {
+ [[clang::noinline]] // unrelated to flatten
+ if (Y) bar(Y);
+ }
+}
+
//CHECK: [[HINT_BRANCH]] = !{!"hlsl.controlflow.hint", i32 1}
//CHECK: [[HINT_FLATTEN]] = !{!"hlsl.controlflow.hint", i32 2}
diff --git a/clang/test/Sema/attr-noinline.cpp b/clang/test/Sema/attr-noinline.cpp
index d6d48321d6604..b16ee660602d0 100644
--- a/clang/test/Sema/attr-noinline.cpp
+++ b/clang/test/Sema/attr-noinline.cpp
@@ -119,3 +119,37 @@ void use() {
qux<3>(0); // #QUX_INST
variadic_qux<0, 1, 2>(0); // #QUX_VARIADIC_INST
}
+
+// Statement attributes are mutually exclusive
+void caller() {
+ [[clang::noinline, clang::always_inline]] bar(); // expected-error {{'clang::always_inline' and 'clang::noinline' attributes are not compatible}} \
+ // expected-note {{conflicting attribute is here}}
+
+ [[clang::always_inline, clang::noinline]] bar(); // expected-error {{'clang::noinline' and 'clang::always_inline' attributes are not compatible}} \
+ // expected-note {{conflicting attribute is here}}
+}
+
+// Attributes on redeclared functions are mutually exclusive
+[[clang::noinline]] void redecl_fn(); // expected-note {{conflicting attribute is here}}
+[[clang::always_inline]] void redecl_fn() {} // expected-error {{'clang::always_inline' and 'clang::noinline' attributes are not compatible}}
+
+[[clang::always_inline]] void redecl_fn2(); // expected-note {{conflicting attribute is here}}
+[[clang::noinline]] void redecl_fn2() {} // expected-error {{'clang::noinline' and 'clang::always_inline' attributes are not compatible}}
+
+// Attributes on the same declaration are mutually exclusive
+[[clang::noinline, clang::always_inline]] void decl_fn(); // expected-error {{'clang::always_inline' and 'clang::noinline' attributes are not compatible}} \
+ // expected-note {{conflicting attribute is here}}
+
+// Explicit specialization should not inherit inline attributes
+template <typename T>
+[[clang::noinline]] void tmpl_fn(T);
+
+template <>
+[[clang::always_inline]] void tmpl_fn(int); // no error expected
+
+// Check
diff erent spellings
+[[gnu::noinline]] void spelling_fn(); // expected-note {{conflicting attribute is here}}
+[[gnu::always_inline]] void spelling_fn() {} // expected-error {{'gnu::always_inline' and 'gnu::noinline' attributes are not compatible}}
+
+__attribute__((noinline)) void spelling_fn2(); // expected-note {{conflicting attribute is here}}
+__attribute__((always_inline)) void spelling_fn2() {} // expected-error {{'always_inline' and 'noinline' attributes are not compatible}}
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