[PATCH] D120395: [X86] Prohibit arithmatic operations on type `__bfloat16`

[Phoebe Wang via Phabricator via cfe-commits]

pengfei created this revision.
pengfei added reviewers: skan, RKSimon, craig.topper, FreddyYe, LuoYuanke.
pengfei requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

`__bfloat16` is defined as X86 specific type that represents the brain
floating-point format. It is only usable with X86 intrinsics. Arithmatic
operations with this type need to be forbidden.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D120395

Files:
  clang/lib/Headers/avx512bf16intrin.h
  clang/lib/Headers/avx512vlbf16intrin.h
  clang/test/CodeGen/X86/avx512bf16-error.c


Index: clang/test/CodeGen/X86/avx512bf16-error.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/X86/avx512bf16-error.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -ffreestanding -triple x86_64-linux-pc %s
+
+// expected-error at +1 3 {{unknown type name '__bfloat16'}}
+__bfloat16 foo(__bfloat16 a, __bfloat16 b) {
+  return a + b;
+}
+
+#include <immintrin.h>
+
+// expected-error at +2 {{invalid operands to binary expression ('__bfloat16' (aka 'struct __bfloat16_s') and '__bfloat16')}}
+__bfloat16 bar(__bfloat16 a, __bfloat16 b) {
+  return a + b;
+}
Index: clang/lib/Headers/avx512vlbf16intrin.h
===================================================================
--- clang/lib/Headers/avx512vlbf16intrin.h
+++ clang/lib/Headers/avx512vlbf16intrin.h
@@ -415,9 +415,10 @@
 ///    and fraction field is truncated to 7 bits.
 static __inline__ __bfloat16 __DEFAULT_FN_ATTRS128 _mm_cvtness_sbh(float __A) {
   __v4sf __V = {__A, 0, 0, 0};
-  __v8hi __R = __builtin_ia32_cvtneps2bf16_128_mask(
+  __v8hi __R1 = __builtin_ia32_cvtneps2bf16_128_mask(
       (__v4sf)__V, (__v8hi)_mm_undefined_si128(), (__mmask8)-1);
-  return __R[0];
+  __bfloat16 __R2 = {__R1[0]};
+  return __R2;
 }
 
 /// Convert Packed BF16 Data to Packed float Data.
Index: clang/lib/Headers/avx512bf16intrin.h
===================================================================
--- clang/lib/Headers/avx512bf16intrin.h
+++ clang/lib/Headers/avx512bf16intrin.h
@@ -15,7 +15,14 @@
 
 typedef short __m512bh __attribute__((__vector_size__(64), __aligned__(64)));
 typedef short __m256bh __attribute__((__vector_size__(32), __aligned__(32)));
-typedef unsigned short __bfloat16;
+
+/// \typedef __bfloat16
+///    A target specific type to represent the storage only brain floating-point
+///    format type. Define through structure to explicitly prohibit any
+///    arithmatic operations.
+typedef struct __bfloat16_s {
+  short _Value;
+} __bfloat16;
 
 #define __DEFAULT_FN_ATTRS512 \
   __attribute__((__always_inline__, __nodebug__, __target__("avx512bf16"), \
@@ -34,7 +41,7 @@
 /// \returns A float data whose sign field and exponent field keep unchanged,
 ///    and fraction field is extended to 23 bits.
 static __inline__ float __DEFAULT_FN_ATTRS _mm_cvtsbh_ss(__bfloat16 __A) {
-  return __builtin_ia32_cvtsbf162ss_32(__A);
+  return __builtin_ia32_cvtsbf162ss_32(__A._Value);
 }
 
 /// Convert Two Packed Single Data to One Packed BF16 Data.


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