base/dispatch-x86ish.S (dispatch_x86ish_cpuid): Skip `EFLAGS_ID' dance on AMD64.

The 64-bit instruction set postdates the `cpuid' instruction.

diff --git a/base/dispatch-x86ish.S b/base/dispatch-x86ish.S
index 8a4c7b2..3a14c39 100644 (file)
--- a/base/dispatch-x86ish.S
+++ b/base/dispatch-x86ish.S
@@ -67,7 +67,9 @@ FUNC(dispatch_x86ish_cpuid)
   endprologue
 
        // First, check that this is even a thing, using the complicated
-       // dance with the flags register.
+       // dance with the flags register.  This is unnecessary on AMD64,
+       // which postdates the introduction of `cpuid'.
+#if CPUFAM_X86
        pushf
        pop     DX                      // current flags in d
 
@@ -86,6 +88,7 @@ FUNC(dispatch_x86ish_cpuid)
        pop     DX
        test    edx, EFLAGS_ID
        jnz     8f
+#endif
 
        // OK, that seemed to work.
        cpuid
@@ -108,6 +111,7 @@ FUNC(dispatch_x86ish_cpuid)
        ret
 
        // Failed.
+#if CPUFAM_X86
 8:     xor     eax, eax
        mov     [OUT + 0], eax
        mov     [OUT + 4], eax
@@ -115,6 +119,7 @@ FUNC(dispatch_x86ish_cpuid)
        mov     [OUT + 12], eax
        mov     eax, -1
        jmp     9b
+#endif
 ENDFUNC
 
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