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llvm-project/clang/test/CodeGen/ms_abi.c
Aiden Grossman e2d7cd685d
[IR] Make dead_on_return attribute optionally sized 
This patch makes the dead_on_return parameter attribute optionally require a number
of bytes to be passed in to specify the number of bytes known to be dead
upon function return/unwind. This is aimed at enabling annotating the
this pointer in C++ destructors with dead_on_return in clang. We need
this to handle cases like the following:

```
struct X {
  int n;
  ~X() {
    this[n].n = 0;
  }
};
void f() {
  X xs[] = {42, -1};
}
```

Where we only certain that sizeof(X) bytes are dead upon return of ~X.
Otherwise DSE would be able to eliminate the store in ~X which would not
be correct.

This patch only does the wiring within IR. Future patches will make
clang emit correct sizing information and update DSE to only delete
stores to objects marked dead_on_return that are provably in bounds of
the number of bytes specified to be dead_on_return.

Reviewers: nikic, alinas, antoniofrighetto

Pull Request: https://github.com/llvm/llvm-project/pull/171712
2026-01-21 08:22:05 -08:00

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// RUN: %clang_cc1 -triple x86_64-unknown-freebsd10.0 -emit-llvm < %s | FileCheck -check-prefix=FREEBSD %s
// RUN: %clang_cc1 -triple x86_64-pc-win32 -emit-llvm < %s | FileCheck -check-prefix=WIN64 %s
// RUN: %clang_cc1 -triple x86_64-mingw -emit-llvm < %s | FileCheck -check-prefix=WIN64 %s
// RUN: %clang_cc1 -triple x86_64-cygwin -emit-llvm < %s | FileCheck -check-prefix=WIN64 %s
// RUN: %clang_cc1 -triple x86_64-uefi -emit-llvm < %s | FileCheck -check-prefix=WIN64 %s
struct foo {
int x;
float y;
char z;
};
// FREEBSD: %[[STRUCT_FOO:.*]] = type { i32, float, i8 }
// WIN64: %[[STRUCT_FOO:.*]] = type { i32, float, i8 }
void __attribute__((ms_abi)) f1(void);
void __attribute__((sysv_abi)) f2(void);
void f3(void) {
// FREEBSD-LABEL: define{{.*}} void @f3()
// WIN64-LABEL: define dso_local void @f3()
f1();
// FREEBSD: call win64cc void @f1()
// WIN64: call void @f1()
f2();
// FREEBSD: call void @f2()
// WIN64: call x86_64_sysvcc void @f2()
}
// FREEBSD: declare win64cc void @f1()
// FREEBSD: declare void @f2()
// WIN64: declare dso_local void @f1()
// WIN64: declare dso_local x86_64_sysvcc void @f2()
// Win64 ABI varargs
void __attribute__((ms_abi)) f4(int a, ...) {
// FREEBSD-LABEL: define{{.*}} win64cc void @f4
// WIN64-LABEL: define dso_local void @f4
__builtin_ms_va_list ap;
__builtin_ms_va_start(ap, a);
// FREEBSD: %[[AP:.*]] = alloca ptr
// FREEBSD: call void @llvm.va_start
// WIN64: %[[AP:.*]] = alloca ptr
// WIN64: call void @llvm.va_start
int b = __builtin_va_arg(ap, int);
// FREEBSD: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
// WIN64: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
double _Complex c = __builtin_va_arg(ap, double _Complex);
// FREEBSD: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
// FREEBSD-NEXT: load ptr, ptr %[[AP_CUR2]]
// WIN64: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
// WIN64-NEXT: load ptr, ptr %[[AP_CUR2]]
struct foo d = __builtin_va_arg(ap, struct foo);
// FREEBSD: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
// FREEBSD-NEXT: load ptr, ptr %[[AP_CUR3]]
// WIN64: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
// WIN64-NEXT: load ptr, ptr %[[AP_CUR3]]
__builtin_ms_va_list ap2;
__builtin_ms_va_copy(ap2, ap);
// FREEBSD: %[[AP_VAL:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: store ptr %[[AP_VAL]], ptr %[[AP2:.*]]
// WIN64: %[[AP_VAL:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: store ptr %[[AP_VAL]], ptr %[[AP2:.*]]
__builtin_ms_va_end(ap);
// FREEBSD: call void @llvm.va_end
// WIN64: call void @llvm.va_end
}
// Let's verify that normal va_lists work right on Win64, too.
void f5(int a, ...) {
// WIN64-LABEL: define dso_local void @f5
__builtin_va_list ap;
__builtin_va_start(ap, a);
// WIN64: %[[AP:.*]] = alloca ptr
// WIN64: call void @llvm.va_start
int b = __builtin_va_arg(ap, int);
// WIN64: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
double _Complex c = __builtin_va_arg(ap, double _Complex);
// WIN64: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
struct foo d = __builtin_va_arg(ap, struct foo);
// WIN64: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
__builtin_va_list ap2;
__builtin_va_copy(ap2, ap);
// WIN64: call void @llvm.va_copy
__builtin_va_end(ap);
// WIN64: call void @llvm.va_end
}
// Verify that using a Win64 va_list from a System V function works.
void __attribute__((sysv_abi)) f6(__builtin_ms_va_list ap) {
// FREEBSD-LABEL: define{{.*}} void @f6
// FREEBSD: store ptr %ap, ptr %[[AP:.*]]
// WIN64-LABEL: define dso_local x86_64_sysvcc void @f6
// WIN64: store ptr %ap, ptr %[[AP:.*]]
int b = __builtin_va_arg(ap, int);
// FREEBSD: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
// WIN64: %[[AP_CUR:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT]], ptr %[[AP]]
double _Complex c = __builtin_va_arg(ap, double _Complex);
// FREEBSD: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
// WIN64: %[[AP_CUR2:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT2:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR2]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT2]], ptr %[[AP]]
struct foo d = __builtin_va_arg(ap, struct foo);
// FREEBSD: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
// FREEBSD-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
// WIN64: %[[AP_CUR3:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: %[[AP_NEXT3:.*]] = getelementptr inbounds i8, ptr %[[AP_CUR3]], i64 8
// WIN64-NEXT: store ptr %[[AP_NEXT3]], ptr %[[AP]]
__builtin_ms_va_list ap2;
__builtin_ms_va_copy(ap2, ap);
// FREEBSD: %[[AP_VAL:.*]] = load ptr, ptr %[[AP]]
// FREEBSD-NEXT: store ptr %[[AP_VAL]], ptr %[[AP2:.*]]
// WIN64: %[[AP_VAL:.*]] = load ptr, ptr %[[AP]]
// WIN64-NEXT: store ptr %[[AP_VAL]], ptr %[[AP2:.*]]
}
// This test checks if structs are passed according to Win64 calling convention
// when it's enforced by __attribute((ms_abi)).
struct i128 {
unsigned long long a;
unsigned long long b;
};
__attribute__((ms_abi)) struct i128 f7(struct i128 a) {
// WIN64: define dso_local void @f7(ptr dead_on_unwind noalias writable sret(%struct.i128) align 8 %agg.result, ptr noundef dead_on_return %a)
// FREEBSD: define{{.*}} win64cc void @f7(ptr dead_on_unwind noalias writable sret(%struct.i128) align 8 %agg.result, ptr noundef dead_on_return %a)
return a;
}
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