e9c2e0acd7
We had a test claiming that this empty struct type consumes a register slot when passing it to a function with GCC, but that does not appear to be the case, at least with GCC versions going back to 4.8. This also caused a miscompilation when passing one of these structs to a variadic function, but it turned out that our implementation of `va_arg` matches GCC's ABI, so the one change fixes both bugs.
113 lines
3.4 KiB
C++
113 lines
3.4 KiB
C++
// RUN: %clang_cc1 -triple arm64-apple-ios7.0 -target-abi darwinpcs -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,DARWIN
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -emit-llvm -o - -x c %s | FileCheck %s --check-prefixes=CHECK,C
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -emit-llvm -o - %s | FileCheck %s --check-prefixes=CHECK,CXX
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// Empty structs are ignored for PCS purposes on Darwin and in C mode elsewhere.
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// In C++ mode on ELF they consume a register slot though. Functions are
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// slightly bigger than minimal to make confirmation against actual GCC
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// behaviour easier.
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#if __cplusplus
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#define EXTERNC extern "C"
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#else
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#define EXTERNC
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#endif
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struct Empty {};
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// DARWIN: define{{.*}} i32 @empty_arg(i32 noundef %a)
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// C: define{{.*}} i32 @empty_arg(i32 noundef %a)
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// CXX: define{{.*}} i32 @empty_arg(i8 %e.coerce, i32 noundef %a)
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EXTERNC int empty_arg(struct Empty e, int a) {
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return a;
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}
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// DARWIN: define{{.*}} void @empty_ret()
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// C: define{{.*}} void @empty_ret()
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// CXX: define{{.*}} void @empty_ret()
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EXTERNC struct Empty empty_ret(void) {
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struct Empty e;
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return e;
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}
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// However, what counts as "empty" is a baroque mess. This is super-empty, it's
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// ignored even in C++ mode. It also has sizeof == 0, violating C++, but that's
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// legacy for you:
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struct SuperEmpty {
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int arr[0];
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};
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// DARWIN: define{{.*}} i32 @super_empty_arg(i32 noundef %a)
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// C: define{{.*}} i32 @super_empty_arg(i32 noundef %a)
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// CXX: define{{.*}} i32 @super_empty_arg(i32 noundef %a)
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EXTERNC int super_empty_arg(struct SuperEmpty e, int a) {
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return a;
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}
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// This is also not empty, and non-standard. We previously considered it to
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// consume a register slot, but GCC does not, so we match that.
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struct SortOfEmpty {
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struct SuperEmpty e;
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};
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// DARWIN: define{{.*}} i32 @sort_of_empty_arg(i32 noundef %a)
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// C: define{{.*}} i32 @sort_of_empty_arg(i32 noundef %a)
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// CXX: define{{.*}} i32 @sort_of_empty_arg(i32 noundef %a)
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EXTERNC int sort_of_empty_arg(struct SortOfEmpty e, int a) {
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return a;
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}
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// DARWIN: define{{.*}} void @sort_of_empty_ret()
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// C: define{{.*}} void @sort_of_empty_ret()
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// CXX: define{{.*}} void @sort_of_empty_ret()
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EXTERNC struct SortOfEmpty sort_of_empty_ret(void) {
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struct SortOfEmpty e;
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return e;
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}
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#include <stdarg.h>
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// va_arg matches the above rules, consuming an incoming argument in cases
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// where one would be passed, and not doing so when the argument should be
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// ignored.
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EXTERNC struct Empty empty_arg_variadic(int a, ...) {
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// CHECK-LABEL: @empty_arg_variadic(
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// DARWIN-NOT: {{ getelementptr }}
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// C-NOT: {{ getelementptr }}
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// CXX: %new_reg_offs = add i32 %gr_offs, 8
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// CXX: %new_stack = getelementptr inbounds i8, ptr %stack, i64 8
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va_list vl;
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va_start(vl, a);
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struct Empty b = va_arg(vl, struct Empty);
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va_end(vl);
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return b;
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}
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EXTERNC struct SuperEmpty super_empty_arg_variadic(int a, ...) {
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// CHECK-LABEL: @super_empty_arg_variadic(
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// DARWIN-NOT: {{ getelementptr }}
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// C-NOT: {{ getelementptr }}
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// CXX-NOT: {{ getelementptr }}
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va_list vl;
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va_start(vl, a);
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struct SuperEmpty b = va_arg(vl, struct SuperEmpty);
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va_end(vl);
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return b;
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}
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EXTERNC struct SortOfEmpty sort_of_empty_arg_variadic(int a, ...) {
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// CHECK-LABEL: @sort_of_empty_arg_variadic(
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// DARWIN: %argp.next = getelementptr inbounds i8, ptr %argp.cur, i64 0
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// C-NOT: {{ getelementptr }}
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// CXX-NOT: {{ getelementptr }}
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va_list vl;
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va_start(vl, a);
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struct SortOfEmpty b = va_arg(vl, struct SortOfEmpty);
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va_end(vl);
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return b;
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}
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