[Guile-commits] 277/437: x86_64: Correct wrong inline assembly in jit_get_cpu

[Andy Wingo]

wingo pushed a commit to branch lightning
in repository guile.

commit dbb9fe1e81ca8c684ea902a59a4889c7345c45ee
Author: pcpa <address@hidden>
Date:   Wed Feb 19 15:29:26 2014 -0300

    x86_64: Correct wrong inline assembly in jit_get_cpu
    
        * lib/jit_x86.c: Rewrite incorrect inline assembly that could
        truncate a variable in a callee save register. Now it simply
        tells gcc that the register is clobbered, instead of using a
        *32 bit* swap with a temporary variable. The problem only
        happens when compiling with optimization.
---
 ChangeLog     |  8 ++++++++
 lib/jit_x86.c | 10 ++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 81d3919..f3ab5a0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2014-19-02 Paulo Andrade <address@hidden>
 
+       * lib/jit_x86.c: Rewrite incorrect inline assembly that could
+       truncate a variable in a callee save register. Now it simply
+       tells gcc that the register is clobbered, instead of using a
+       *32 bit* swap with a temporary variable. The problem only
+       happens when compiling with optimization.
+
+2014-19-02 Paulo Andrade <address@hidden>
+
        * include/lightning/jit_aarch64.h, include/lightning/jit_arm.h,
        include/lightning/jit_hppa.h, include/lightning/jit_ia64.h,
        include/lightning/jit_mips.h, include/lightning/jit_ppc.h,
diff --git a/lib/jit_x86.c b/lib/jit_x86.c
index 69df289..027e6db 100644
--- a/lib/jit_x86.c
+++ b/lib/jit_x86.c
@@ -236,10 +236,11 @@ jit_get_cpu(void)
 #endif
 
     /* query %eax = 1 function */
-    __asm__ volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
+    __asm__ volatile ("cpuid; movl %%ebx, %1"
                      : "=a" (eax), "=r" (ebx),
                      "=c" (ecx.cpuid), "=d" (edx.cpuid)
-                     : "0" (1));
+                     : "0" (1)
+                     : "ebx");
 
     jit_cpu.fpu                = edx.bits.fpu;
     jit_cpu.cmpxchg8b  = edx.bits.cmpxchg8b;
@@ -261,10 +262,11 @@ jit_get_cpu(void)
 
 #if __WORDSIZE == 64
     /* query %eax = 0x80000001 function */
-    __asm__ volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
+    __asm__ volatile ("cpuid; movl %%ebx, %1"
                      : "=a" (eax), "=r" (ebx),
                      "=c" (ecx.cpuid), "=d" (edx.cpuid)
-                     : "0" (0x80000001));
+                     : "0" (0x80000001)
+                     : "ebx");
     jit_cpu.lahf       = ecx.cpuid & 1;
 #endif
 }