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-rw-r--r--Eigen/src/Core/util/Memory.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/Eigen/src/Core/util/Memory.h b/Eigen/src/Core/util/Memory.h
index b26afda64..3d0994415 100644
--- a/Eigen/src/Core/util/Memory.h
+++ b/Eigen/src/Core/util/Memory.h
@@ -751,9 +751,10 @@ public:
# if defined(__PIC__) && defined(__i386__)
// Case for x86 with PIC
# define EIGEN_CPUID(abcd,func,id) \
- __asm__ __volatile__ ("xchgl %%ebx, %%esi;cpuid; xchgl %%ebx,%%esi": "=a" (abcd[0]), "=S" (abcd[1]), "=c" (abcd[2]), "=d" (abcd[3]) : "a" (func), "c" (id));
+ __asm__ __volatile__ ("xchgl %%ebx, %k1;cpuid; xchgl %%ebx,%k1": "=a" (abcd[0]), "=&r" (abcd[1]), "=c" (abcd[2]), "=d" (abcd[3]) : "a" (func), "c" (id));
# elif defined(__PIC__) && defined(__x86_64__)
- // Case for x64 with PIC
+ // Case for x64 with PIC. In theory this is only a problem with recent gcc and with medium or large code model, not with the default small code model.
+ // However, we cannot detect which code model is used, and the xchg overhead is negligible anyway.
# define EIGEN_CPUID(abcd,func,id) \
__asm__ __volatile__ ("xchg{q}\t{%%}rbx, %q1; cpuid; xchg{q}\t{%%}rbx, %q1": "=a" (abcd[0]), "=&r" (abcd[1]), "=c" (abcd[2]), "=d" (abcd[3]) : "0" (func), "2" (id));
# else