X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/catacomb/blobdiff_plain/981a9e5d5e3af6c06ad8b3f821928852068227e4..00b52725bf15e844360d07248de1d8cbbc1e165e:/base/dispatch-x86ish.S

diff --git a/base/dispatch-x86ish.S b/base/dispatch-x86ish.S
index 57d8d32b..9510f969 100644
--- a/base/dispatch-x86ish.S
+++ b/base/dispatch-x86ish.S
@@ -154,6 +154,39 @@ FUNC(dispatch_x86ish_xmmregisters_p)
 	ret
 ENDFUNC
 
+///--------------------------------------------------------------------------
+/// Checking extended control registers.
+
+FUNC(dispatch_x86ish_xgetbv)
+	// Call with two arguments: a pointer Z_OUT to 8 bytes of output space, and
+	// a 32-bit integer C.  Read the 64-bit value of XCR(C), and store it
+	// at Z_OUT.
+
+#if CPUFAM_X86
+#  define Z_OUT edi
+	mov	edi, [esp + 4]
+	mov	ecx, [esp + 8]
+#endif
+#if CPUFAM_AMD64 && ABI_SYSV
+#  define Z_OUT rdi
+	mov	ecx, esi
+#endif
+#if CPUFAM_AMD64 && ABI_WIN
+#  define Z_OUT r8
+	mov	r8, rcx
+	mov	ecx, edx
+#endif
+  endprologue
+
+	xgetbv
+	mov	[Z_OUT + 0], eax
+	mov	[Z_OUT + 4], edx
+
+	ret
+
+#undef Z_OUT
+ENDFUNC
+
 ///--------------------------------------------------------------------------
 /// Checking `rdrand'.