[clang] 3e499e9 - [CIR] Add support for common linkage (#168613)
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Tue Nov 18 14:51:27 PST 2025
Author: Andy Kaylor
Date: 2025-11-18T14:51:23-08:00
New Revision: 3e499e9427e006a4204d1cb5b6eebe957844e06e
URL: https://github.com/llvm/llvm-project/commit/3e499e9427e006a4204d1cb5b6eebe957844e06e
DIFF: https://github.com/llvm/llvm-project/commit/3e499e9427e006a4204d1cb5b6eebe957844e06e.diff
LOG: [CIR] Add support for common linkage (#168613)
Add support for marking global variables with common linkage.
Added:
clang/test/CIR/CodeGen/no-common.c
Modified:
clang/lib/CIR/CodeGen/CIRGenModule.cpp
Removed:
################################################################################
diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index 4a82ea3121b60..b8e51f87d4045 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -883,8 +883,17 @@ void CIRGenModule::emitGlobalVarDefinition(const clang::VarDecl *vd,
// FIXME(cir): setLinkage should likely set MLIR's visibility automatically.
gv.setVisibility(getMLIRVisibilityFromCIRLinkage(linkage));
assert(!cir::MissingFeatures::opGlobalDLLImportExport());
- if (linkage == cir::GlobalLinkageKind::CommonLinkage)
- errorNYI(initExpr->getSourceRange(), "common linkage");
+ if (linkage == cir::GlobalLinkageKind::CommonLinkage) {
+ // common vars aren't constant even if declared const.
+ gv.setConstant(false);
+ // Tentative definition of global variables may be initialized with
+ // non-zero null pointers. In this case they should have weak linkage
+ // since common linkage must have zero initializer and must not have
+ // explicit section therefore cannot have non-zero initial value.
+ std::optional<mlir::Attribute> initializer = gv.getInitialValue();
+ if (initializer && !getBuilder().isNullValue(*initializer))
+ gv.setLinkage(cir::GlobalLinkageKind::WeakAnyLinkage);
+ }
setNonAliasAttributes(vd, gv);
@@ -1238,10 +1247,8 @@ cir::GlobalLinkageKind CIRGenModule::getCIRLinkageForDeclarator(
// linkage.
if (!getLangOpts().CPlusPlus && isa<VarDecl>(dd) &&
!isVarDeclStrongDefinition(astContext, *this, cast<VarDecl>(dd),
- getCodeGenOpts().NoCommon)) {
- errorNYI(dd->getBeginLoc(), "common linkage", dd->getDeclKindName());
+ getCodeGenOpts().NoCommon))
return cir::GlobalLinkageKind::CommonLinkage;
- }
// selectany symbols are externally visible, so use weak instead of
// linkonce. MSVC optimizes away references to const selectany globals, so
diff --git a/clang/test/CIR/CodeGen/no-common.c b/clang/test/CIR/CodeGen/no-common.c
new file mode 100644
index 0000000000000..ce4c5fc0b3a33
--- /dev/null
+++ b/clang/test/CIR/CodeGen/no-common.c
@@ -0,0 +1,103 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -emit-cir -o %t-default.cir
+// RUN: FileCheck --input-file=%t-default.cir %s -check-prefix=CIR-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -fno-common -emit-cir -o %t-no-common.cir
+// RUN: FileCheck --input-file=%t-no-common.cir %s -check-prefix=CIR-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -fcommon -emit-cir -o %t-common.cir
+// RUN: FileCheck --input-file=%t-common.cir %s -check-prefix=CIR-COMMON
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -emit-llvm -o %t-default-cir.ll
+// RUN: FileCheck --input-file=%t-default-cir.ll %s -check-prefix=LLVM-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -fno-common -emit-llvm -o %t-no-common-cir.ll
+// RUN: FileCheck --input-file=%t-no-common-cir.ll %s -check-prefix=LLVM-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir %s -fcommon -emit-llvm -o %t-common-cir.ll
+// RUN: FileCheck --input-file=%t-common-cir.ll %s -check-prefix=LLVM-COMMON
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu %s -emit-llvm -o %t-default.ll
+// RUN: FileCheck --input-file=%t-default.ll %s -check-prefix=OGCG-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu %s -fno-common -emit-llvm -o %t-no-common.ll
+// RUN: FileCheck --input-file=%t-no-common.ll %s -check-prefix=OGCG-DEFAULT
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu %s -fcommon -emit-llvm -o %t-common.ll
+// RUN: FileCheck --input-file=%t-common.ll %s -check-prefix=OGCG-COMMON
+
+const int a = 42;
+// CIR-DEFAULT: cir.global constant external @a = #cir.int<42>
+// LLVM-DEFAULT: @a = constant i32 42
+// OGCG-DEFAULT: @a = constant i32 42
+
+// CIR-COMMON: cir.global constant external @a
+// LLVM-COMMON: @a = constant i32 42
+// OGCG-COMMON: @a = constant i32 42
+
+const int b __attribute__((common)) = 42;
+// CIR-DEFAULT: cir.global constant external @b = #cir.int<42>
+// LLVM-DEFAULT: @b = constant i32 42
+// OGCG-DEFAULT: @b = constant i32 42
+
+// CIR-COMMON: cir.global constant external @b = #cir.int<42>
+// LLVM-COMMON: @b = constant i32 42
+// OGCG-COMMON: @b = constant i32 42
+
+const int c __attribute__((nocommon)) = 42;
+// CIR-DEFAULT: cir.global constant external @c = #cir.int<42>
+// LLVM-DEFAULT: @c = constant i32 42
+// OGCG-DEFAULT: @c = constant i32 42
+
+// CIR-COMMON: cir.global constant external @c = #cir.int<42>
+// LLVM-COMMON: @c = constant i32 42
+// OGCG-COMMON: @c = constant i32 42
+
+int d = 11;
+// CIR-DEFAULT: cir.global external @d = #cir.int<11>
+// LLVM-DEFAULT: @d = global i32 11
+// OGCG-DEFAULT: @d = global i32 11
+
+// CIR-COMMON: cir.global external @d = #cir.int<11>
+// LLVM-COMMON: @d = global i32 11
+// OGCG-COMMON: @d = global i32 11
+
+int e;
+// CIR-DEFAULT: cir.global external @e = #cir.int<0>
+// LLVM-DEFAULT: @e = global i32 0
+// OGCG-DEFAULT: @e = global i32 0
+
+// CIR-COMMON: cir.global common @e = #cir.int<0>
+// LLVM-COMMON: @e = common global i32 0
+// OGCG-COMMON: @e = common global i32 0
+
+
+int f __attribute__((common));
+// CIR-DEFAULT: cir.global common @f = #cir.int<0>
+// LLVM-DEFAULT: @f = common global i32 0
+// OGCG-DEFAULT: @f = common global i32 0
+
+// CIR-COMMON: cir.global common @f
+// LLVM-COMMON: @f = common global i32 0
+// OGCG-COMMON: @f = common global i32 0
+
+int g __attribute__((nocommon));
+// CIR-DEFAULT: cir.global external @g = #cir.int<0>
+// LLVM-DEFAULT: @g = global i32
+// OGCG-DEFAULT: @g = global i32 0
+
+// CIR-COMMON: cir.global external @g = #cir.int<0>
+// LLVM-COMMON: @g = global i32 0
+// OGCG-COMMON: @g = global i32 0
+
+const int h;
+// CIR-DEFAULT: cir.global constant external @h = #cir.int<0>
+// LLVM-DEFAULT: @h = constant i32
+// OGCG-DEFAULT: @h = constant i32 0
+
+// CIR-COMMON: cir.global common @h = #cir.int<0>
+// LLVM-COMMON: @h = common global i32 0
+// OGCG-COMMON: @h = common global i32 0
+
+typedef void* (*fn_t)(long a, long b, char *f, int c);
+fn_t ABC __attribute__ ((nocommon));
+// CIR-DEFAULT: cir.global external @ABC = #cir.ptr<null>
+// LLVM-DEFAULT: @ABC = global ptr null
+// OGCG-DEFAULT: @ABC = global ptr null
+
+// CIR-COMMON: cir.global external @ABC = #cir.ptr<null>
+// LLVM-COMMON: @ABC = global ptr null
+// OGCG-COMMON: @ABC = global ptr null
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