[clang][RISCV][test] Add test cases for empty structs and the FP calling conventions

[asb]

Summary

As reported in https://github.com/llvm/llvm-project/issues/58929, Clang currently differs from GCC in the handling of empty structs. This commit adds some test coverage for the handling of such structs.

Posting for review rather than committing directly because more eyes on our test coverage for in these areas would be useful.

A follow-up patch implements a fix to match g++.

[luismarques]

LGTM but others should also chime in.

clang/test/CodeGen/RISCV/abi-empty-structs.c

102

Should we also test a case with an array size 0 like ct s { struct empty e[0]; float f; };? I think that's a GNU extension and I don't expect the result to be different but...

[asb]

clang/test/CodeGen/RISCV/abi-empty-structs.c

102

Good idea and thanks for the review. As it stands, this patch has the bare minimum set of tests I'd be happy to land the ABI test fix. I'll try and do another pass to add in more tomorrow.

[asb]

Add zero-length array test cases.

[luismarques]

clang/test/CodeGen/RISCV/abi-empty-structs.c

1

Assume you updated this test with the not yet committed --full-function-signature option and forgot to remove that before updating the patch?
Please also check if the newly added %s below are supposed to be there.

[asb]

clang/test/CodeGen/RISCV/abi-empty-structs.c

1

The newly added %s are correct - it was an issue in the earlier patch that didn't impact update_cc_test_checks but did impact lit.

I think in order to land this ahead of the update_test_checks I'd remove this line and add perhaps add a FIXME comment to refresh the file once that patch lands.

clang/test/CodeGen/RISCV/abi-empty-structs.c

+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --function-signature --full-function-signature --filter "^define |^entry:"
+// RUN: %clang_cc1 -triple riscv32 -target-feature +f -target-abi ilp32f -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-C,CHECK32-C %s
+// RUN: %clang_cc1 -triple riscv32 -target-feature +f -target-feature +d -target-abi ilp32d -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-C,CHECK32-C %s
+// RUN: %clang_cc1 -triple riscv64 -target-feature +f -target-abi lp64f -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-C,CHECK64-C %s
+// RUN: %clang_cc1 -triple riscv64 -target-feature +f -target-feature +d -target-abi lp64d -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-C,CHECK64-C %s
+// RUN: %clang_cc1 -x c++ -triple riscv32 -target-feature +f -target-abi ilp32f -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-CXX,CHECK32-CXX %s
+// RUN: %clang_cc1 -x c++ -triple riscv32 -target-feature +f -target-feature +d -target-abi ilp32d -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-CXX,CHECK32-CXX %s
+// RUN: %clang_cc1 -x c++ -triple riscv64 -target-feature +f -target-abi lp64f -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-CXX,CHECK64-CXX %s
+// RUN: %clang_cc1 -x c++ -triple riscv64 -target-feature +f -target-feature +d -target-abi lp64d -emit-llvm %s -o - \
+// RUN:   | FileCheck -check-prefixes=CHECK-CXX,CHECK64-CXX %s
+
+#include <stdint.h>
+
+// Fields containing empty structs or unions are ignored when flattening
+// structs for the hard FP ABIs, even in C++.
+// FIXME: This isn't currently respected.
+
+struct empty { struct { struct { } e; }; };
+struct s1 { struct empty e; float f; };
+
+// CHECK-C-LABEL: define dso_local float @test_s1
+// CHECK-C-SAME: (float [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local [2 x i32] @_Z7test_s12s1
+// CHECK32-CXX-SAME: ([2 x i32] [[A_COERCE:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local i64 @_Z7test_s12s1
+// CHECK64-CXX-SAME: (i64 [[A_COERCE:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK64-CXX:  entry:
+//
+struct s1 test_s1(struct s1 a) {
+  return a;
+}
+
+struct s2 { struct empty e; int32_t i; float f; };
+
+// CHECK-C-LABEL: define dso_local { i32, float } @test_s2
+// CHECK-C-SAME: (i32 [[TMP0:%.*]], float [[TMP1:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local void @_Z7test_s22s2
+// CHECK32-CXX-SAME: (ptr noalias sret([[STRUCT_S2:%.*]]) align 4 [[AGG_RESULT:%.*]], ptr noundef [[A:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local [2 x i64] @_Z7test_s22s2
+// CHECK64-CXX-SAME: ([2 x i64] [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s2 test_s2(struct s2 a) {
+  return a;
+}
+
+struct s3 { struct empty e; float f; float g; };
+
+// CHECK-C-LABEL: define dso_local { float, float } @test_s3
+// CHECK-C-SAME: (float [[TMP0:%.*]], float [[TMP1:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local void @_Z7test_s32s3
+// CHECK32-CXX-SAME: (ptr noalias sret([[STRUCT_S3:%.*]]) align 4 [[AGG_RESULT:%.*]], ptr noundef [[A:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local [2 x i64] @_Z7test_s32s3
+// CHECK64-CXX-SAME: ([2 x i64] [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s3 test_s3(struct s3 a) {
+  return a;
+}
+
+struct s4 { struct empty e; float __complex__ c; };
+
+// CHECK-C-LABEL: define dso_local { float, float } @test_s4
+// CHECK-C-SAME: (float [[TMP0:%.*]], float [[TMP1:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local void @_Z7test_s42s4
+// CHECK32-CXX-SAME: (ptr noalias sret([[STRUCT_S4:%.*]]) align 4 [[AGG_RESULT:%.*]], ptr noundef [[A:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local [2 x i64] @_Z7test_s42s4
+// CHECK64-CXX-SAME: ([2 x i64] [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s4 test_s4(struct s4 a) {
+  return a;
+}
+
+// An array of empty fields isn't ignored in C++ (this isn't explicit in the
+// psABI, but matches observed g++ behaviour).
+
+struct s5 { struct empty e[1]; float f; };
+
+// CHECK-C-LABEL: define dso_local float @test_s5
+// CHECK-C-SAME: (float [[TMP0:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local [2 x i32] @_Z7test_s52s5
+// CHECK32-CXX-SAME: ([2 x i32] [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local i64 @_Z7test_s52s5
+// CHECK64-CXX-SAME: (i64 [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s5 test_s5(struct s5 a) {
+  return a;
+}
+
+struct empty_arr { struct { struct { } e[1]; }; };
+struct s6 { struct empty_arr e; float f; };
+
+// CHECK-C-LABEL: define dso_local float @test_s6
+// CHECK-C-SAME: (float [[TMP0:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local [2 x i32] @_Z7test_s62s6
+// CHECK32-CXX-SAME: ([2 x i32] [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local i64 @_Z7test_s62s6
+// CHECK64-CXX-SAME: (i64 [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s6 test_s6(struct s6 a) {
+  return a;
+}
+
+struct s7 { struct empty e[0]; float f; };
+
+// CHECK-C-LABEL: define dso_local float @test_s7
+// CHECK-C-SAME: (float [[TMP0:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK-CXX-LABEL: define dso_local float @_Z7test_s72s7
+// CHECK-CXX-SAME: (float [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-CXX:  entry:
+//
+struct s7 test_s7(struct s7 a) {
+  return a;
+}
+
+struct empty_arr0 { struct { struct { } e[0]; }; };
+struct s8 { struct empty_arr0 e; float f; };
+
+// CHECK-C-LABEL: define dso_local float @test_s8
+// CHECK-C-SAME: (float [[TMP0:%.*]]) #[[ATTR0]] {
+// CHECK-C:  entry:
+//
+// CHECK32-CXX-LABEL: define dso_local i32 @_Z7test_s82s8
+// CHECK32-CXX-SAME: (i32 [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK32-CXX:  entry:
+//
+// CHECK64-CXX-LABEL: define dso_local i64 @_Z7test_s82s8
+// CHECK64-CXX-SAME: (i64 [[A_COERCE:%.*]]) #[[ATTR0]] {
+// CHECK64-CXX:  entry:
+//
+struct s8 test_s8(struct s8 a) {
+  return a;
+}
+
+//// NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+// CHECK32-C: {{.*}}
+// CHECK64-C: {{.*}}