commit 791fe5ecf909d573bcbf353b677b9404f9da0ed4
Author: Mark Wielaard <mark@klomp.org>
Date:   Mon May 27 22:19:27 2019 +0200

    Expose rdrand and f16c through cpuid also if the host only has avx.
    
    The amd64 CPUID dirtyhelpers are mostly static since they emulate some
    existing CPU "family". The avx2 ("i7-4910MQ") CPUID variant however
    can "dynamicly" enable rdrand and/or f16c if the host supports them.
    Do the same for the avx_and_cx16 ("i5-2300") CPUID variant.
    
    https://bugs.kde.org/show_bug.cgi?id=408009

diff --git a/VEX/priv/guest_amd64_defs.h b/VEX/priv/guest_amd64_defs.h
index 4f34b41..a5de527 100644
--- a/VEX/priv/guest_amd64_defs.h
+++ b/VEX/priv/guest_amd64_defs.h
@@ -165,7 +165,9 @@ extern void  amd64g_dirtyhelper_storeF80le ( Addr/*addr*/, ULong/*data*/ );
 extern void  amd64g_dirtyhelper_CPUID_baseline ( VexGuestAMD64State* st );
 extern void  amd64g_dirtyhelper_CPUID_sse3_and_cx16 ( VexGuestAMD64State* st );
 extern void  amd64g_dirtyhelper_CPUID_sse42_and_cx16 ( VexGuestAMD64State* st );
-extern void  amd64g_dirtyhelper_CPUID_avx_and_cx16 ( VexGuestAMD64State* st );
+extern void  amd64g_dirtyhelper_CPUID_avx_and_cx16 ( VexGuestAMD64State* st,
+                                                     ULong hasF16C,
+                                                     ULong hasRDRAND );
 extern void  amd64g_dirtyhelper_CPUID_avx2 ( VexGuestAMD64State* st,
                                              ULong hasF16C, ULong hasRDRAND );
 
diff --git a/VEX/priv/guest_amd64_helpers.c b/VEX/priv/guest_amd64_helpers.c
index e4cf7e2..182bae0 100644
--- a/VEX/priv/guest_amd64_helpers.c
+++ b/VEX/priv/guest_amd64_helpers.c
@@ -3141,8 +3141,11 @@ void amd64g_dirtyhelper_CPUID_sse42_and_cx16 ( VexGuestAMD64State* st )
    address sizes   : 36 bits physical, 48 bits virtual
    power management:
 */
-void amd64g_dirtyhelper_CPUID_avx_and_cx16 ( VexGuestAMD64State* st )
+void amd64g_dirtyhelper_CPUID_avx_and_cx16 ( VexGuestAMD64State* st,
+                                             ULong hasF16C, ULong hasRDRAND )
 {
+   vassert((hasF16C >> 1) == 0ULL);
+   vassert((hasRDRAND >> 1) == 0ULL);
 #  define SET_ABCD(_a,_b,_c,_d)                \
       do { st->guest_RAX = (ULong)(_a);        \
            st->guest_RBX = (ULong)(_b);        \
@@ -3157,9 +3160,14 @@ void amd64g_dirtyhelper_CPUID_avx_and_cx16 ( VexGuestAMD64State* st )
       case 0x00000000:
          SET_ABCD(0x0000000d, 0x756e6547, 0x6c65746e, 0x49656e69);
          break;
-      case 0x00000001:
-         SET_ABCD(0x000206a7, 0x00100800, 0x1f9ae3bf, 0xbfebfbff);
+      case 0x00000001: {
+         // As a baseline, advertise neither F16C (ecx:29) nor RDRAND (ecx:30),
+         // but patch in support for them as directed by the caller.
+         UInt ecx_extra
+            = (hasF16C ? (1U << 29) : 0) | (hasRDRAND ? (1U << 30) : 0);
+         SET_ABCD(0x000206a7, 0x00100800, (0x1f9ae3bf | ecx_extra), 0xbfebfbff);
          break;
+      }
       case 0x00000002:
          SET_ABCD(0x76035a01, 0x00f0b0ff, 0x00000000, 0x00ca0000);
          break;
diff --git a/VEX/priv/guest_amd64_toIR.c b/VEX/priv/guest_amd64_toIR.c
index 56e992c..96dee38 100644
--- a/VEX/priv/guest_amd64_toIR.c
+++ b/VEX/priv/guest_amd64_toIR.c
@@ -22007,7 +22007,8 @@ Long dis_ESC_0F (
 
       vassert(fName); vassert(fAddr);
       IRExpr** args = NULL;
-      if (fAddr == &amd64g_dirtyhelper_CPUID_avx2) {
+      if (fAddr == &amd64g_dirtyhelper_CPUID_avx2
+          || fAddr == &amd64g_dirtyhelper_CPUID_avx_and_cx16) {
          Bool hasF16C   = (archinfo->hwcaps & VEX_HWCAPS_AMD64_F16C) != 0;
          Bool hasRDRAND = (archinfo->hwcaps & VEX_HWCAPS_AMD64_RDRAND) != 0;
          args = mkIRExprVec_3(IRExpr_GSPTR(),
diff --git a/coregrind/m_machine.c b/coregrind/m_machine.c
index 3536e57..56a28d1 100644
--- a/coregrind/m_machine.c
+++ b/coregrind/m_machine.c
@@ -1076,10 +1076,10 @@ Bool VG_(machine_get_hwcaps)( void )
         have_avx2 = (ebx & (1<<5)) != 0; /* True => have AVX2 */
      }
 
-     /* Sanity check for RDRAND and F16C.  These don't actually *need* AVX2, but
-        it's convenient to restrict them to the AVX2 case since the simulated
-        CPUID we'll offer them on has AVX2 as a base. */
-     if (!have_avx2) {
+     /* Sanity check for RDRAND and F16C.  These don't actually *need* AVX, but
+        it's convenient to restrict them to the AVX case since the simulated
+        CPUID we'll offer them on has AVX as a base. */
+     if (!have_avx) {
         have_f16c   = False;
         have_rdrand = False;
      }