base/dispatch.c, rand/rand.c, and asm: Support `rdseed' for quick noise.

[catacomb] / rand / rand-x86ish.S

diff --git a/rand/rand-x86ish.S b/rand/rand-x86ish.S
index 61de2b8..b91a937 100644 (file)
--- a/rand/rand-x86ish.S
+++ b/rand/rand-x86ish.S
@@ -37,6 +37,17 @@
 ///--------------------------------------------------------------------------
 /// Quick random generation.
 
+// Common register allocation.
+#if CPUFAM_X86
+#  define COUNT ecx
+#endif
+#if CPUFAM_AMD64 && ABI_SYSV
+#  define COUNT ecx
+#endif
+#if CPUFAM_AMD64 && ABI_WIN
+#  define COUNT r8d
+#endif
+
 FUNC(rand_quick_x86ish_rdrand)
        // Enter with a pointer to the random context in the first argument.
        // Return zero on success, or -1 on error.
@@ -44,15 +55,12 @@ FUNC(rand_quick_x86ish_rdrand)
 #if CPUFAM_X86
        mov     edx, [SP + 4]
        stalloc 28
-#  define COUNT ecx
 #endif
 #if CPUFAM_AMD64 && ABI_SYSV
        stalloc 8
-#  define COUNT ecx
 #endif
 #if CPUFAM_AMD64 && ABI_WIN
        stalloc 40
-#  define COUNT r8d
 #endif
   endprologue
 
@@ -66,6 +74,34 @@ FUNC(rand_quick_x86ish_rdrand)
        // Failed.
        mov     eax, -1
        jmp     9f
+ENDFUNC
+
+FUNC(rand_quick_x86ish_rdseed)
+       // Enter with a pointer to the random context in the first argument.
+       // Return zero on success, or -1 on error.
+
+#if CPUFAM_X86
+       mov     edx, [SP + 4]
+       stalloc 28
+#endif
+#if CPUFAM_AMD64 && ABI_SYSV
+       stalloc 8
+#endif
+#if CPUFAM_AMD64 && ABI_WIN
+       stalloc 40
+#endif
+  endprologue
+
+       // Try to fetch a random number.
+       mov     COUNT, 16
+0:     rdseed  AX
+       jc      1f
+       dec     COUNT
+       jnz     0b
+
+       // Failed.
+       mov     eax, -1
+       jmp     9f
 
        // Success.
 1:
@@ -106,4 +142,6 @@ FUNC(rand_quick_x86ish_rdrand)
        ret
 ENDFUNC
 
+#undef COUNT
+
 ///----- That's all, folks --------------------------------------------------