From: Mat <mberchtold@gmail.com>
Date: Mon, 29 May 2017 09:06:26 +0000 (+0200)
Subject: Fix: wrong register for BMI1 bit (#112)
X-Git-Tag: 1.9.9-b1~660^2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fdb5552727c44e08793b89fdd8aab48559a12fa9;p=thirdparty%2Fzlib-ng.git

Fix: wrong register for BMI1 bit (#112)

The BMI1 bit is in the ebx register and not in ecx.
See reference: https://software.intel.com/sites/default/files/article/405250/how-to-detect-new-instruction-support-in-the-4th-generation-intel-core-processor-family.pdf
---

diff --git a/arch/x86/x86.c b/arch/x86/x86.c
index cd933745f..45bd63de2 100644
--- a/arch/x86/x86.c
+++ b/arch/x86/x86.c
@@ -54,5 +54,7 @@ void ZLIB_INTERNAL x86_check_features(void) {
 
 	cpuid(7, &eax, &ebx, &ecx, &edx);
 
-	x86_cpu_has_tzcnt = ecx & 0x8;
+	// check BMI1 bit
+	// Reference: https://software.intel.com/sites/default/files/article/405250/how-to-detect-new-instruction-support-in-the-4th-generation-intel-core-processor-family.pdf
+	x86_cpu_has_tzcnt = ebx & 0x8;
 }