sunfish updated this revision to Diff 234942.
sunfish added a comment.
To support a transition to the new system, temporarily define a `__main_void`
alias for no-argument `main`. This allows libc to detect whether it's calling
old-style or new-style main and do the right thing.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D70700/new/
https://reviews.llvm.org/D70700
Files:
clang/lib/AST/Mangle.cpp
clang/lib/CodeGen/CodeGenModule.cpp
clang/lib/CodeGen/CodeGenModule.h
clang/lib/Frontend/InitHeaderSearch.cpp
clang/test/CodeGen/wasm-call-main.c
clang/test/CodeGen/wasm-main.c
clang/test/CodeGen/wasm-main_argc_argv.c
llvm/include/llvm/ADT/Triple.h
Index: llvm/include/llvm/ADT/Triple.h
===================================================================
--- llvm/include/llvm/ADT/Triple.h
+++ llvm/include/llvm/ADT/Triple.h
@@ -730,6 +730,11 @@
return getArch() == Triple::riscv32 || getArch() == Triple::riscv64;
}
+ /// Tests whether the target is wasm (32- and 64-bit).
+ bool isWasm() const {
+ return getArch() == Triple::wasm32 || getArch() == Triple::wasm64;
+ }
+
/// Tests whether the target supports comdat
bool supportsCOMDAT() const {
return !isOSBinFormatMachO();
Index: clang/test/CodeGen/wasm-main_argc_argv.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/wasm-main_argc_argv.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm %s | FileCheck %s
+
+// Mangle the argc/argv form of main.
+
+int main(int argc, char **argv) {
+ return 0;
+}
+
+// CHECK-LABEL: define i32 @__main_argc_argv(i32 %argc, i8** %argv)
Index: clang/test/CodeGen/wasm-main.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/wasm-main.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm %s | FileCheck %s
+
+// Don't mangle the no-arg form of main.
+
+int main(void) {
+ return 0;
+}
+
+// CHECK-LABEL: define i32 @main()
Index: clang/test/CodeGen/wasm-call-main.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/wasm-call-main.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm %s | FileCheck %s
+
+// Mangle argc/argv main even when it's not defined in this TU.
+
+#include <stddef.h>
+
+int main(int argc, char *argv[]);
+
+int foo(void) {
+ return main(0, NULL);
+}
+
+// CHECK: call i32 @__main_argc_argv(
Index: clang/lib/Frontend/InitHeaderSearch.cpp
===================================================================
--- clang/lib/Frontend/InitHeaderSearch.cpp
+++ clang/lib/Frontend/InitHeaderSearch.cpp
@@ -435,8 +435,7 @@
break;
case llvm::Triple::UnknownOS:
- if (triple.getArch() == llvm::Triple::wasm32 ||
- triple.getArch() == llvm::Triple::wasm64)
+ if (triple.isWasm())
return;
break;
}
Index: clang/lib/CodeGen/CodeGenModule.h
===================================================================
--- clang/lib/CodeGen/CodeGenModule.h
+++ clang/lib/CodeGen/CodeGenModule.h
@@ -1012,6 +1012,9 @@
/// for the uninstrumented functions.
void EmitDeferredUnusedCoverageMappings();
+ /// Emit an alias for "main" if it has no arguments (needed for wasm).
+ void EmitMainVoidAlias();
+
/// Tell the consumer that this variable has been instantiated.
void HandleCXXStaticMemberVarInstantiation(VarDecl *VD);
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -447,6 +447,10 @@
CodeGenFunction(*this).EmitCfiCheckStub();
}
emitAtAvailableLinkGuard();
+ if (Context.getTargetInfo().getTriple().isWasm() &&
+ !Context.getTargetInfo().getTriple().isOSEmscripten()) {
+ EmitMainVoidAlias();
+ }
emitLLVMUsed();
if (SanStats)
SanStats->finish();
@@ -5579,6 +5583,17 @@
}
}
+void CodeGenModule::EmitMainVoidAlias() {
+ // In order to transition away from "__original_main" gracefully, emit an
+ // alias for "main" in the no-argument case so that libc can detect when
+ // new-style no-argument main is in used.
+ if (llvm::Function *F = getModule().getFunction("main")) {
+ if (!F->isDeclaration() && F->arg_size() == 0 && !F->isVarArg() &&
+ F->getReturnType()->isIntegerTy(Context.getTargetInfo().getIntWidth()))
+ addUsedGlobal(llvm::GlobalAlias::create("__main_void", F));
+ }
+}
+
/// Turns the given pointer into a constant.
static llvm::Constant *GetPointerConstant(llvm::LLVMContext &Context,
const void *Ptr) {
Index: clang/lib/AST/Mangle.cpp
===================================================================
--- clang/lib/AST/Mangle.cpp
+++ clang/lib/AST/Mangle.cpp
@@ -50,7 +50,8 @@
CCM_Fast,
CCM_RegCall,
CCM_Vector,
- CCM_Std
+ CCM_Std,
+ CCM_WasmMainArgcArgv
};
static bool isExternC(const NamedDecl *ND) {
@@ -63,6 +64,16 @@
const NamedDecl *ND) {
const TargetInfo &TI = Context.getTargetInfo();
const llvm::Triple &Triple = TI.getTriple();
+
+ // On wasm, the argc/argv form of "main" is renamed so that the startup code
+ // can call it with the correct function signature.
+ // On Emscripten, users may be exporting "main" and expecting to call it
+ // themselves, so we can't mangle it.
+ if (Triple.isWasm() && !Triple.isOSEmscripten())
+ if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
+ if (FD->isMain() && FD->hasPrototype() && FD->param_size() == 2)
+ return CCM_WasmMainArgcArgv;
+
if (!Triple.isOSWindows() ||
!(Triple.getArch() == llvm::Triple::x86 ||
Triple.getArch() == llvm::Triple::x86_64))
@@ -145,6 +156,12 @@
const ASTContext &ASTContext = getASTContext();
CCMangling CC = getCallingConvMangling(ASTContext, D);
+
+ if (CC == CCM_WasmMainArgcArgv) {
+ Out << "__main_argc_argv";
+ return;
+ }
+
bool MCXX = shouldMangleCXXName(D);
const TargetInfo &TI = Context.getTargetInfo();
if (CC == CCM_Other || (MCXX && TI.getCXXABI() == TargetCXXABI::Microsoft)) {
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