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Subject[PATCH 07/11] x86-64: Simplify constraints for fxsave/fxtstor
Date
Use the "R" constraint (legacy register) instead of listing all the
possible registers. Clean up the comments as well.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
arch/x86/include/asm/i387.h | 44 ++++++++++++++++--------------------------
1 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 8b40a83..768fcb2 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -81,6 +81,7 @@ static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
{
int err;

+ /* See comment in fxsave() below. */
asm volatile("1: rex64/fxrstor (%[fx])\n\t"
"2:\n"
".section .fixup,\"ax\"\n"
@@ -89,11 +90,7 @@ static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
".previous\n"
_ASM_EXTABLE(1b, 3b)
: [err] "=r" (err)
-#if 0 /* See comment in fxsave() below. */
- : [fx] "r" (fx), "m" (*fx), "0" (0));
-#else
- : [fx] "cdaSDb" (fx), "m" (*fx), "0" (0));
-#endif
+ : [fx] "R" (fx), "m" (*fx), "0" (0));
return err;
}

@@ -140,6 +137,7 @@ static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
if (unlikely(err))
return -EFAULT;

+ /* See comment in fxsave() below. */
asm volatile("1: rex64/fxsave (%[fx])\n\t"
"2:\n"
".section .fixup,\"ax\"\n"
@@ -148,11 +146,7 @@ static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
".previous\n"
_ASM_EXTABLE(1b, 3b)
: [err] "=r" (err), "=m" (*fx)
-#if 0 /* See comment in fxsave() below. */
- : [fx] "r" (fx), "0" (0));
-#else
- : [fx] "cdaSDb" (fx), "0" (0));
-#endif
+ : [fx] "R" (fx), "0" (0));
if (unlikely(err) &&
__clear_user(fx, sizeof(struct i387_fxsave_struct)))
err = -EFAULT;
@@ -165,26 +159,22 @@ static inline void fpu_fxsave(struct fpu *fpu)
/* Using "rex64; fxsave %0" is broken because, if the memory operand
uses any extended registers for addressing, a second REX prefix
will be generated (to the assembler, rex64 followed by semicolon
- is a separate instruction), and hence the 64-bitness is lost. */
-#if 0
- /* Using "fxsaveq %0" would be the ideal choice, but is only supported
- starting with gas 2.16. */
- __asm__ __volatile__("fxsaveq %0"
- : "=m" (fpu->state->fxsave));
-#elif 0
- /* Using, as a workaround, the properly prefixed form below isn't
+ is a separate instruction), and hence the 64-bitness is lost.
+ Using "fxsaveq %0" would be the ideal choice, but is only supported
+ starting with gas 2.16.
+ asm volatile("fxsaveq %0"
+ : "=m" (fpu->state->fxsave));
+ Using, as a workaround, the properly prefixed form below isn't
accepted by any binutils version so far released, complaining that
the same type of prefix is used twice if an extended register is
- needed for addressing (fix submitted to mainline 2005-11-21). */
- __asm__ __volatile__("rex64/fxsave %0"
- : "=m" (fpu->state->fxsave));
-#else
- /* This, however, we can work around by forcing the compiler to select
+ needed for addressing (fix submitted to mainline 2005-11-21).
+ asm volatile("rex64/fxsave %0"
+ : "=m" (fpu->state->fxsave));
+ This, however, we can work around by forcing the compiler to select
an addressing mode that doesn't require extended registers. */
- __asm__ __volatile__("rex64/fxsave (%1)"
- : "=m" (fpu->state->fxsave)
- : "cdaSDb" (&fpu->state->fxsave));
-#endif
+ asm volatile("rex64/fxsave (%[fx])"
+ : "=m" (fpu->state->fxsave)
+ : [fx] "R" (&fpu->state->fxsave));
}

static inline void fpu_save_init(struct fpu *fpu)
--
1.7.2.2


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