[clang] [llvm] [clang][CodeGen] Construct function type for callgraph from function definition (PR #212863)
Prabhu Rajasekaran via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 19 15:57:45 PDT 2026
https://github.com/Prabhuk updated https://github.com/llvm/llvm-project/pull/212863
>From cde7374ccfeae9003d0d81228b3fbf47ed61c01d Mon Sep 17 00:00:00 2001
From: prabhukr <prabhukr at google.com>
Date: Wed, 29 Jul 2026 13:11:36 -0700
Subject: [PATCH 1/2] [clang][CodeGen] Construct function type for callgraph
from function definition
When -fexperimental-call-graph-section is enabled, for unprototyped function
definitions (such as C89 parameterless declarations or K&R definitions)
reconstruct their prototype from the parameter declarations in the
definition AST (applying default argument promotions to parameters).
---
clang/lib/CodeGen/CodeGenModule.cpp | 37 +++++++++++-
...all-graph-section-definition-noprototype.c | 57 +++++++++++++++++++
clang/test/CodeGen/call-graph-section.c | 4 +-
.../Linker/callgraph-section-noprototype.ll | 42 ++++++++++++++
4 files changed, 135 insertions(+), 5 deletions(-)
create mode 100644 clang/test/CodeGen/call-graph-section-definition-noprototype.c
create mode 100644 llvm/test/Linker/callgraph-section-noprototype.ll
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index e7c1d182fd20d..f19cfd6f07157 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3464,11 +3464,38 @@ void CodeGenModule::createIndirectFunctionTypeMD(const FunctionDecl *FD,
F->getFunction().hasAddressTaken(nullptr, /*IgnoreCallbackUses=*/true,
/*IgnoreAssumeLikeCalls=*/true,
/*IgnoreLLVMUsed=*/false)) {
+ const FunctionDecl *Def = nullptr;
+ bool HasBody = FD->hasBody(Def);
+ if (!HasBody || !Def)
+ Def = FD;
+
+ QualType QT = Def->getType();
+ if (const auto *FNPT = QT->getAs<FunctionNoProtoType>()) {
+ // If there is no definition available in this TU for an unprototyped
+ // function declaration, skip generating incomplete callgraph metadata.
+ if (!HasBody && !Def->isThisDeclarationADefinition())
+ return;
+
+ SmallVector<QualType, 8> ParamTypes;
+ for (const ParmVarDecl *P : Def->parameters()) {
+ QualType ParamTy = P->getType();
+ if (Context.isPromotableIntegerType(ParamTy))
+ ParamTy = Context.getPromotedIntegerType(ParamTy);
+ else if (const auto *BT = ParamTy->getAs<BuiltinType>()) {
+ if (BT->getKind() == BuiltinType::Float ||
+ BT->getKind() == BuiltinType::Half)
+ ParamTy = Context.DoubleTy;
+ }
+ ParamTypes.push_back(ParamTy);
+ }
+ FunctionProtoType::ExtProtoInfo EPI;
+ QT = Context.getFunctionType(FNPT->getReturnType(), ParamTypes, EPI);
+ }
+
F->addMetadata(
llvm::LLVMContext::MD_callgraph,
- *llvm::MDTuple::get(
- getLLVMContext(),
- {CreateMetadataIdentifierForCallGraphType(FD->getType())}));
+ *llvm::MDTuple::get(getLLVMContext(),
+ {CreateMetadataIdentifierForCallGraphType(QT)}));
}
}
@@ -8636,6 +8663,10 @@ llvm::Metadata *CodeGenModule::CreateMetadataIdentifierGeneralized(QualType T) {
llvm::Metadata *
CodeGenModule::CreateMetadataIdentifierForCallGraphType(QualType T) {
+ if (auto *FNPT = T->getAs<FunctionNoProtoType>()) {
+ FunctionProtoType::ExtProtoInfo EPI;
+ T = getContext().getFunctionType(FNPT->getReturnType(), {}, EPI);
+ }
return CreateMetadataIdentifierImpl(T, CallGraphMetadataIdMap, "",
/*ForceString=*/true);
}
diff --git a/clang/test/CodeGen/call-graph-section-definition-noprototype.c b/clang/test/CodeGen/call-graph-section-definition-noprototype.c
new file mode 100644
index 0000000000000..21193ff8aca92
--- /dev/null
+++ b/clang/test/CodeGen/call-graph-section-definition-noprototype.c
@@ -0,0 +1,57 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fexperimental-call-graph-section \
+// RUN: -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,ITANIUM %s
+
+// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc -fexperimental-call-graph-section \
+// RUN: -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,MS %s
+
+// Tests that function definitions specified without a prototype (C89 empty parameter list or K&R declarations)
+// generate !callgraph metadata based on reconstructed parameter types (with default argument promotions).
+
+// Forward declaration without prototype (pure declaration in this TU).
+// Because there is no definition or prototype in this TU, no !callgraph metadata is attached to @decl_only declaration.
+// CHECK-LABEL: declare {{.*}}void @decl_only(...)
+void decl_only();
+
+void use_decl() {
+ void (*fp)() = decl_only;
+}
+
+// C89 definition with no parameters: reconstructed prototype void (void).
+// CHECK-LABEL: define {{(dso_local)?}} void @foo(
+// CHECK-SAME: {{.*}} !callgraph [[F_TVOID:![0-9]+]]
+void foo() {
+}
+
+// Function returning struct pointer with no parameters: reconstructed prototype struct my_struct *(void).
+struct my_struct;
+// CHECK-LABEL: define {{(dso_local)?}} ptr @create_my_struct(
+// CHECK-SAME: {{.*}} !callgraph [[F_TMY_STRUCT:![0-9]+]]
+struct my_struct *create_my_struct() {
+ return 0;
+}
+
+// Function returning int with no parameters: reconstructed prototype int (void).
+// CHECK-LABEL: define {{(dso_local)?}} i32 @baz(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT:![0-9]+]]
+int baz() {
+ return 1;
+}
+
+// K&R function definition: reconstructed prototype void (int, int) with promoted short -> int.
+// CHECK-LABEL: define {{(dso_local)?}} void @knr_func(
+// CHECK-SAME: {{.*}} !callgraph [[F_TKNR:![0-9]+]]
+void knr_func(a, b)
+ int a;
+ short b;
+{
+}
+
+// ITANIUM: [[F_TVOID]] = !{!"_ZTSFvvE"}
+// ITANIUM: [[F_TMY_STRUCT]] = !{!"_ZTSFP9my_structvE"}
+// ITANIUM: [[F_TINT]] = !{!"_ZTSFivE"}
+// ITANIUM: [[F_TKNR]] = !{!"_ZTSFviiE"}
+
+// MS: [[F_TVOID]] = !{!"?6AXXZ"}
+// MS: [[F_TMY_STRUCT]] = !{!"?6APEAUmy_struct@@XZ"}
+// MS: [[F_TINT]] = !{!"?6AHXZ"}
+// MS: [[F_TKNR]] = !{!"?6AXHH at Z"}
diff --git a/clang/test/CodeGen/call-graph-section.c b/clang/test/CodeGen/call-graph-section.c
index cb2f9015b7ff5..1543f30aa2b40 100644
--- a/clang/test/CodeGen/call-graph-section.c
+++ b/clang/test/CodeGen/call-graph-section.c
@@ -74,7 +74,7 @@ void stf() {
fp_stparam(St2, &St2);
}
-// ITANIUM: [[F_TVOID]] = !{!"_ZTSFvE"}
+// ITANIUM: [[F_TVOID]] = !{!"_ZTSFvvE"}
// ITANIUM: [[F_TVOID_CT]] = !{[[F_TVOID:![0-9]+]]}
// ITANIUM: [[F_TPRIMITIVE]] = !{!"_ZTSFicfdE"}
// ITANIUM: [[F_TPTR]] = !{!"_ZTSFPiPcPfPdE"}
@@ -83,7 +83,7 @@ void stf() {
// ITANIUM: [[F_TSTRUCT]] = !{!"_ZTSFv3st2PS_E"}
// ITANIUM: [[F_TSTRUCT_CT]] = !{[[F_TSTRUCT:![0-9]+]]}
-// MS: [[F_TVOID]] = !{!"?6AX at Z"}
+// MS: [[F_TVOID]] = !{!"?6AXXZ"}
// MS: [[F_TVOID_CT]] = !{[[F_TVOID:![0-9]+]]}
// MS: [[F_TPRIMITIVE]] = !{!"?6AHDMN at Z"}
// MS: [[F_TPTR]] = !{!"?6APEAHPEADPEAMPEAN at Z"}
diff --git a/llvm/test/Linker/callgraph-section-noprototype.ll b/llvm/test/Linker/callgraph-section-noprototype.ll
new file mode 100644
index 0000000000000..1b2e77f121ffe
--- /dev/null
+++ b/llvm/test/Linker/callgraph-section-noprototype.ll
@@ -0,0 +1,42 @@
+; RUN: rm -rf %t && split-file %s %t
+; RUN: llvm-link %t/decl.ll %t/def.ll -S | FileCheck %s
+
+; Tests that when linking a declaration module (without !callgraph metadata for unprototyped decl)
+; and a definition module (with full reconstructed !callgraph metadata),
+; the merged definition replaces the declaration and retains the definition's !callgraph metadata.
+
+; CHECK: define dso_local void @bar()
+; CHECK: call void (i32, i32, ...) %0(i32 noundef 1, i32 noundef 2), !callee_type [[F_CT:![0-9]+]]
+; CHECK: define dso_local void @foo(i32 noundef %a, i32 noundef %0) !callgraph [[F_DEF:![0-9]+]]
+
+; CHECK: [[F_CT]] = !{[[F_DEF]]}
+; CHECK: [[F_DEF]] = !{!"_ZTSFviiE"}
+
+;--- decl.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux"
+
+define dso_local void @bar() {
+entry:
+ %fp = alloca ptr, align 8
+ store ptr @foo, ptr %fp, align 8
+ %0 = load ptr, ptr %fp, align 8
+ call void (i32, i32, ...) %0(i32 noundef 1, i32 noundef 2), !callee_type !1
+ ret void
+}
+
+declare void @foo(...)
+
+!1 = !{!2}
+!2 = !{!"_ZTSFviiE"}
+
+;--- def.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux"
+
+define dso_local void @foo(i32 noundef %a, i32 noundef %0) !callgraph !1 {
+entry:
+ ret void
+}
+
+!1 = !{!"_ZTSFviiE"}
>From 390d54aefe5e1e24574347acfa3c242ccf2af88d Mon Sep 17 00:00:00 2001
From: prabhukr <prabhukr at google.com>
Date: Wed, 19 Aug 2026 22:41:09 +0000
Subject: [PATCH 2/2] Fix the test. Test for promotion normalization
expectations. Test for call site and definitions side reconstructed prototype
matching.
---
...all-graph-section-definition-noprototype.c | 107 ++++++++++++------
1 file changed, 75 insertions(+), 32 deletions(-)
diff --git a/clang/test/CodeGen/call-graph-section-definition-noprototype.c b/clang/test/CodeGen/call-graph-section-definition-noprototype.c
index 21193ff8aca92..9cf93e4892199 100644
--- a/clang/test/CodeGen/call-graph-section-definition-noprototype.c
+++ b/clang/test/CodeGen/call-graph-section-definition-noprototype.c
@@ -1,57 +1,100 @@
+/// Tests that function definitions without a prototype (C89 empty parameter list or K&R declarations)
+/// reconstruct parameter types with default argument promotions and produce type identifiers that
+/// match both:
+/// - Their prototyped equivalents on the definition side.
+/// - Indirect callsites using unprototyped function pointers.
+
// RUN: %clang_cc1 -triple x86_64-unknown-linux -fexperimental-call-graph-section \
// RUN: -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,ITANIUM %s
// RUN: %clang_cc1 -triple x86_64-pc-windows-msvc -fexperimental-call-graph-section \
// RUN: -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,MS %s
-// Tests that function definitions specified without a prototype (C89 empty parameter list or K&R declarations)
-// generate !callgraph metadata based on reconstructed parameter types (with default argument promotions).
-
-// Forward declaration without prototype (pure declaration in this TU).
-// Because there is no definition or prototype in this TU, no !callgraph metadata is attached to @decl_only declaration.
+/// Forward declaration without prototype (pure declaration in this TU).
+/// Because there is no definition or prototype in this TU, no !callgraph metadata is attached.
// CHECK-LABEL: declare {{.*}}void @decl_only(...)
void decl_only();
-void use_decl() {
+void use_decl(void) {
void (*fp)() = decl_only;
}
-// C89 definition with no parameters: reconstructed prototype void (void).
-// CHECK-LABEL: define {{(dso_local)?}} void @foo(
+/// Void parameter list: C89 parameterless definition and C prototyped (void) definition
+/// must produce the same type identifier.
+// CHECK-LABEL: define {{(dso_local)?}} void @proto_void(
// CHECK-SAME: {{.*}} !callgraph [[F_TVOID:![0-9]+]]
-void foo() {
-}
+void proto_void(void) {}
+
+// CHECK-LABEL: define {{(dso_local)?}} void @c89_void(
+// CHECK-SAME: {{.*}} !callgraph [[F_TVOID]]
+void c89_void() {}
+
+/// Single argument promotion: K&R int definition and K&R short definition (promoted to int)
+/// must produce the same type identifier.
+// CHECK-LABEL: define {{(dso_local)?}} void @knr_int(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT_ONE:![0-9]+]]
+void knr_int(i)
+ int i;
+{}
+
+// CHECK-LABEL: define {{(dso_local)?}} void @knr_promoted_int(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT_ONE]]
+void knr_promoted_int(i)
+ short i;
+{}
+
+/// Multi-argument promotions: prototyped (int, double), K&R (int, double), and K&R (short, float)
+/// (promoted to int, double) must all produce the same type identifier.
+// CHECK-LABEL: define {{(dso_local)?}} void @proto_int_double(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT_DOUBLE:![0-9]+]]
+void proto_int_double(int a, double b) {}
+
+// CHECK-LABEL: define {{(dso_local)?}} void @knr_int_double(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT_DOUBLE]]
+void knr_int_double(a, b)
+ int a;
+ double b;
+{}
+
+// CHECK-LABEL: define {{(dso_local)?}} void @knr_promoted_multi(
+// CHECK-SAME: {{.*}} !callgraph [[F_TINT_DOUBLE]]
+void knr_promoted_multi(a, b)
+ short a;
+ float b;
+{}
-// Function returning struct pointer with no parameters: reconstructed prototype struct my_struct *(void).
+/// Struct pointer return: C89 parameterless and prototyped (void) return types must match.
struct my_struct;
-// CHECK-LABEL: define {{(dso_local)?}} ptr @create_my_struct(
+
+// CHECK-LABEL: define {{(dso_local)?}} ptr @proto_my_struct(
// CHECK-SAME: {{.*}} !callgraph [[F_TMY_STRUCT:![0-9]+]]
-struct my_struct *create_my_struct() {
- return 0;
-}
+struct my_struct *proto_my_struct(void) { return 0; }
-// Function returning int with no parameters: reconstructed prototype int (void).
-// CHECK-LABEL: define {{(dso_local)?}} i32 @baz(
-// CHECK-SAME: {{.*}} !callgraph [[F_TINT:![0-9]+]]
-int baz() {
- return 1;
-}
+// CHECK-LABEL: define {{(dso_local)?}} ptr @c89_my_struct(
+// CHECK-SAME: {{.*}} !callgraph [[F_TMY_STRUCT]]
+struct my_struct *c89_my_struct() { return 0; }
-// K&R function definition: reconstructed prototype void (int, int) with promoted short -> int.
-// CHECK-LABEL: define {{(dso_local)?}} void @knr_func(
-// CHECK-SAME: {{.*}} !callgraph [[F_TKNR:![0-9]+]]
-void knr_func(a, b)
- int a;
- short b;
-{
+/// Callsite-to-definition equivalence: indirect calls using unprototyped function pointers
+/// must generate !callee_type metadata referencing the normalized definition type identifiers.
+void test_indirect_calls(void) {
+ // CHECK: call void {{.*}}, !callee_type [[F_TVOID_CT:![0-9]+]]
+ void (*fp_void)() = c89_void;
+ fp_void();
+
+ // CHECK: call void {{.*}}, !callee_type [[F_TINT_DOUBLE_CT:![0-9]+]]
+ void (*fp_multi)() = knr_promoted_multi;
+ fp_multi((short)1, (float)2.0);
}
// ITANIUM: [[F_TVOID]] = !{!"_ZTSFvvE"}
+// ITANIUM: [[F_TINT_ONE]] = !{!"_ZTSFviE"}
+// ITANIUM: [[F_TINT_DOUBLE]] = !{!"_ZTSFvidE"}
// ITANIUM: [[F_TMY_STRUCT]] = !{!"_ZTSFP9my_structvE"}
-// ITANIUM: [[F_TINT]] = !{!"_ZTSFivE"}
-// ITANIUM: [[F_TKNR]] = !{!"_ZTSFviiE"}
// MS: [[F_TVOID]] = !{!"?6AXXZ"}
+// MS: [[F_TINT_ONE]] = !{!"?6AXH at Z"}
+// MS: [[F_TINT_DOUBLE]] = !{!"?6AXHN at Z"}
// MS: [[F_TMY_STRUCT]] = !{!"?6APEAUmy_struct@@XZ"}
-// MS: [[F_TINT]] = !{!"?6AHXZ"}
-// MS: [[F_TKNR]] = !{!"?6AXHH at Z"}
+
+// CHECK: [[F_TVOID_CT]] = !{[[F_TVOID]]}
+// CHECK: [[F_TINT_DOUBLE_CT]] = !{[[F_TINT_DOUBLE]]}
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