__bfloat16 is redefined from typedef short to real __bf16 since GCC
V13. The patch issues an warning for potential silent implicit
conversion between __bf16 and short where users may only expect a
data movement.
To avoid too many false positive, warning is only under
TARGET_AVX512BF16.
Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}
Ok for trunk?
gcc/ChangeLog:
* config/i386/i386.cc (ix86_invalid_conversion): New function.
(TARGET_INVALID_CONVERSION): Define as
ix86_invalid_conversion.
gcc/testsuite/ChangeLog:
* gcc.target/i386/bf16_short_warn.c: New test.
---
gcc/config/i386/i386.cc | 32 +++++++++++++++++++
.../gcc.target/i386/bf16_short_warn.c | 17 ++++++++++
2 files changed, 49 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/i386/bf16_short_warn.c
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 0761965344b..dc02eac6203 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -22718,6 +22718,35 @@ x86_emit_floatuns (rtx operands[2])
emit_label (donelab);
}
+
+/* Return the diagnostic message string if conversion from FROMTYPE to
+ TOTYPE is not allowed, NULL otherwise.
+ Currently it's used to warn for silent implicit conversion between __bf16
+ and short, since __bfloat16 is refined as real __bf16 instead of short
+ since GCC13. */
+
+static const char *
+ix86_invalid_conversion (const_tree fromtype, const_tree totype)
+{
+ if (element_mode (fromtype) != element_mode (totype)
+ && (TARGET_AVX512BF16 || TARGET_AVXNECONVERT))
+ {
+ /* Warn for silent implicit conversion where user may expect
+ a bitcast. */
+ if ((TYPE_MODE (fromtype) == BFmode
+ && TYPE_MODE (totype) == HImode)
+ || (TYPE_MODE (totype) == BFmode
+ && TYPE_MODE (fromtype) == HImode))
+ warning (0, "%<__bfloat16%> is redefined from typedef %<short%> "
+ "to real %<__bf16%> since GCC V13, be careful of "
+ "implicit conversion between %<__bf16%> and %<short%>; "
+ "a explicit bitcast may be needed here");
+ }
+
+ /* Conversion allowed. */
+ return NULL;
+}
+
/* Target hook for scalar_mode_supported_p. */
static bool
@@ -25009,6 +25038,9 @@ ix86_run_selftests (void)
# define TARGET_MERGE_DECL_ATTRIBUTES merge_dllimport_decl_attributes
#endif
+#undef TARGET_INVALID_CONVERSION
+#define TARGET_INVALID_CONVERSION ix86_invalid_conversion
+
#undef TARGET_COMP_TYPE_ATTRIBUTES
#define TARGET_COMP_TYPE_ATTRIBUTES ix86_comp_type_attributes
diff --git a/gcc/testsuite/gcc.target/i386/bf16_short_warn.c
b/gcc/testsuite/gcc.target/i386/bf16_short_warn.c
new file mode 100644
index 00000000000..3e47a815200
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/bf16_short_warn.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include<immintrin.h>
+typedef struct {
+short payload;
+} BFloat16;
+
+__attribute__((target("avx512vl,avx512bf16")))
+BFloat16 tobf16_avx512(float f)
+{
+ BFloat16 r;
+ __m128bh m = _mm_cvtneps_pbh(_mm_set_ss(f));
+ r.payload = m[0]; /* { dg-warning " be careful of implicit conversion
between '__bf16' and 'short'" } */
+ return r;
+}
+
--
2.39.1.388.g2fc9e9ca3c
