On Wed, 3 May 2023 at 08:10, Richard Henderson
<richard.henderson@linaro.org> wrote:
Notice when Intel or AMD have guaranteed that vmovdqa is atomic.
The new variable will also be used in generated code.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
include/qemu/cpuid.h | 18 ++++++++++++++++++
tcg/i386/tcg-target.h | 1 +
tcg/i386/tcg-target.c.inc | 27 +++++++++++++++++++++++++++
3 files changed, 46 insertions(+)
diff --git a/include/qemu/cpuid.h b/include/qemu/cpuid.h
index 1451e8ef2f..35325f1995 100644
--- a/include/qemu/cpuid.h
+++ b/include/qemu/cpuid.h
@@ -71,6 +71,24 @@
#define bit_LZCNT (1 << 5)
#endif
+/*
+ * Signatures for different CPU implementations as returned from Leaf 0.
+ */
+
+#ifndef signature_INTEL_ecx
+/* "Genu" "ineI" "ntel" */
+#define signature_INTEL_ebx 0x756e6547
+#define signature_INTEL_edx 0x49656e69
+#define signature_INTEL_ecx 0x6c65746e
+#endif
+
+#ifndef signature_AMD_ecx
+/* "Auth" "enti" "cAMD" */
+#define signature_AMD_ebx 0x68747541
+#define signature_AMD_edx 0x69746e65
+#define signature_AMD_ecx 0x444d4163
+#endif
@@ -4024,6 +4025,32 @@ static void tcg_target_init(TCGContext *s)
have_avx512dq = (b7 & bit_AVX512DQ) != 0;
have_avx512vbmi2 = (c7 & bit_AVX512VBMI2) != 0;
}
+
+ /*
+ * The Intel SDM has added:
+ * Processors that enumerate support for Intel® AVX
+ * (by setting the feature flag CPUID.01H:ECX.AVX[bit 28])
+ * guarantee that the 16-byte memory operations performed
+ * by the following instructions will always be carried
+ * out atomically:
+ * - MOVAPD, MOVAPS, and MOVDQA.
+ * - VMOVAPD, VMOVAPS, and VMOVDQA when encoded with VEX.128.
+ * - VMOVAPD, VMOVAPS, VMOVDQA32, and VMOVDQA64 when encoded
+ * with EVEX.128 and k0 (masking disabled).
+ * Note that these instructions require the linear addresses
+ * of their memory operands to be 16-byte aligned.
+ *
+ * AMD has provided an even stronger guarantee that processors
+ * with AVX provide 16-byte atomicity for all cachable,
+ * naturally aligned single loads and stores, e.g. MOVDQU.
+ *
+ * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104688
+ */
+ if (have_avx1) {
+ __cpuid(0, a, b, c, d);
+ have_atomic16 = (c == signature_INTEL_ecx ||
+ c == signature_AMD_ecx);
+ }
If the signature is 3 words why are we only checking one here ?