Refactor detection of x86 ZMM registers

- Call _xgetbv within x86_set_runtime_features rather than in a
  separate function
- Use symbols for XCR mask bits rather than a magic constant

A future commit will build on this to detect YMM registers without
code duplication.

Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Discussion: https://postgr.es/m/CANWCAZbgEUFw7LuYSVeJ=Tj98R5HoOB1Ffeqk3aLvbw5rU5NTw@mail.gmail.com

diff --git a/src/port/pg_cpu_x86.c b/src/port/pg_cpu_x86.c
index 88863f9762c64c94ebaf888ac36274e05d56f820..7575838245cd7275a0b0bf0e369c739dd386b127 100644 (file)
--- a/src/port/pg_cpu_x86.c
+++ b/src/port/pg_cpu_x86.c
@@ -31,32 +31,34 @@
 
 #include "port/pg_cpu.h"
 
+/*
+ * XSAVE state component bits that we need
+ *
+ * https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-1-manual.pdf
+ * Chapter "MANAGING STATE USING THE XSAVE FEATURE SET"
+ */
+#define XMM                    (1<<1)
+#define YMM                    (1<<2)
+#define OPMASK         (1<<5)
+#define ZMM0_15                (1<<6)
+#define ZMM16_31       (1<<7)
+
 
 /* array indexed by enum X86FeatureId */
 bool           X86Features[X86FeaturesSize] = {0};
 
-/*
- * Does XGETBV say the ZMM registers are enabled?
- *
- * NB: Caller is responsible for verifying that osxsave is available
- * before calling this.
- */
-#ifdef HAVE_XSAVE_INTRINSICS
-pg_attribute_target("xsave")
-#endif
 static bool
-zmm_regs_available(void)
+mask_available(uint32 value, uint32 mask)
 {
-#ifdef HAVE_XSAVE_INTRINSICS
-       return (_xgetbv(0) & 0xe6) == 0xe6;
-#else
-       return false;
-#endif
+       return (value & mask) == mask;
 }
 
 /*
  * Parse the CPU ID info for runtime checks.
  */
+#ifdef HAVE_XSAVE_INTRINSICS
+pg_attribute_target("xsave")
+#endif
 void
 set_x86_features(void)
 {
@@ -76,6 +78,8 @@ set_x86_features(void)
        /* All these features depend on OSXSAVE */
        if (exx[2] & (1 << 27))
        {
+               uint32          xcr0_val = 0;
+
                /* second cpuid call on leaf 7 to check extended AVX-512 support */
 
                memset(exx, 0, 4 * sizeof(exx[0]));
@@ -86,7 +90,14 @@ set_x86_features(void)
                __cpuidex(exx, 7, 0);
 #endif
 
-               if (zmm_regs_available())
+#ifdef HAVE_XSAVE_INTRINSICS
+               /* get value of Extended Control Register */
+               xcr0_val = _xgetbv(0);
+#endif
+
+               /* Are ZMM registers enabled? */
+               if (mask_available(xcr0_val, XMM | YMM |
+                                                  OPMASK | ZMM0_15 | ZMM16_31))
                {
                        X86Features[PG_AVX512_BW] = exx[1] >> 30 & 1;
                        X86Features[PG_AVX512_VL] = exx[1] >> 31 & 1;