[PATCH, i386]: Check maximum ext_level before calling CPUID with 0x80000008

[Uros Bizjak]

Hello!

... otherwise we can call CPUID with out-of range level.  Also,
simplify xgetbv checks.

2016-09-29  Uros Bizjak  <ubiz...@gmail.com>

    * config/i386/driver-i386.c (host_detect_local_cpu): Check maximum
    ext_level before calling CPUID with 0x80000008.
    Simplify xgetbv checks.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Committed to mainline SVN.

Uros.

Index: config/i386/driver-i386.c
===================================================================
--- config/i386/driver-i386.c   (revision 240626)
+++ config/i386/driver-i386.c   (working copy)
@@ -517,7 +517,7 @@ const char *host_detect_local_cpu (int argc, const
   /* Check cpuid level of extended features.  */
   __cpuid (0x80000000, ext_level, ebx, ecx, edx);
 
-  if (ext_level > 0x80000000)
+  if (ext_level >= 0x80000001)
     {
       __cpuid (0x80000001, eax, ebx, ecx, edx);
 
@@ -535,7 +535,10 @@ const char *host_detect_local_cpu (int argc, const
       has_3dnowp = edx & bit_3DNOWP;
       has_3dnow = edx & bit_3DNOW;
       has_mwaitx = ecx & bit_MWAITX;
+    }
 
+  if (ext_level >= 0x80000008)
+    {
       __cpuid (0x80000008, eax, ebx, ecx, edx);
       has_clzero = ebx & bit_CLZERO;
     }
@@ -548,14 +551,21 @@ const char *host_detect_local_cpu (int argc, const
 #define XSTATE_OPMASK                  0x20
 #define XSTATE_ZMM                     0x40
 #define XSTATE_HI_ZMM                  0x80
+
+#define XCR_AVX_ENABLED_MASK \
+  (XSTATE_SSE | XSTATE_YMM)
+#define XCR_AVX512F_ENABLED_MASK \
+  (XSTATE_SSE | XSTATE_YMM | XSTATE_OPMASK | XSTATE_ZMM | XSTATE_HI_ZMM)
+
   if (has_osxsave)
     asm (".byte 0x0f; .byte 0x01; .byte 0xd0"
         : "=a" (eax), "=d" (edx)
         : "c" (XCR_XFEATURE_ENABLED_MASK));
+  else
+    eax = 0;
 
-  /* Check if SSE and YMM states are supported.  */
-  if (!has_osxsave
-      || (eax & (XSTATE_SSE | XSTATE_YMM)) != (XSTATE_SSE | XSTATE_YMM))
+  /* Check if AVX registers are supported.  */
+  if ((eax & XCR_AVX_ENABLED_MASK) != XCR_AVX_ENABLED_MASK)
     {
       has_avx = 0;
       has_avx2 = 0;
@@ -569,10 +579,8 @@ const char *host_detect_local_cpu (int argc, const
       has_xsavec = 0;
     }
 
-  if (!has_osxsave
-      || (eax &
-         (XSTATE_SSE | XSTATE_YMM | XSTATE_OPMASK | XSTATE_ZMM | 
XSTATE_HI_ZMM))
-         != (XSTATE_SSE | XSTATE_YMM | XSTATE_OPMASK | XSTATE_ZMM | 
XSTATE_HI_ZMM))
+  /* Check if AVX512F registers are supported.  */
+  if ((eax & XCR_AVX512F_ENABLED_MASK) != XCR_AVX512F_ENABLED_MASK)
     {
       has_avx512f = 0;
       has_avx512er = 0;
@@ -603,7 +611,7 @@ const char *host_detect_local_cpu (int argc, const
       unsigned int name;
 
       /* Detect geode processor by its processor signature.  */
-      if (ext_level > 0x80000001)
+      if (ext_level >= 0x80000002)
        __cpuid (0x80000002, name, ebx, ecx, edx);
       else
        name = 0;