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powerpc: Avoid load hit store in __giveup_fpu() and __giveup_altivec()

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In both __giveup_fpu() and __giveup_altivec() we make two modifications
to tsk->thread.regs->msr. gcc decides to do a read/modify/write of
each change, so we end up with a load hit store:

        ld      r9,264(r10)
        rldicl  r9,r9,50,1
        rotldi  r9,r9,14
        std     r9,264(r10)
...
        ld      r9,264(r10)
        rldicl  r9,r9,40,1
        rotldi  r9,r9,24
        std     r9,264(r10)

Fix this by using a temporary.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Anton Blanchard 2016-05-29 22:03:50 +10:00 committed by Michael Ellerman
parent 5edb56491d
commit 8eb9803723
1 changed files with 12 additions and 4 deletions
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16
arch/powerpc/kernel/process.c
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@ -139,12 +139,16 @@ EXPORT_SYMBOL(__msr_check_and_clear);
#ifdef CONFIG_PPC_FPU
void __giveup_fpu(struct task_struct *tsk)
{
unsigned long msr;
save_fpu(tsk);
tsk->thread.regs->msr &= ~MSR_FP;
msr = tsk->thread.regs->msr;
msr &= ~MSR_FP;
#ifdef CONFIG_VSX
if (cpu_has_feature(CPU_FTR_VSX))
tsk->thread.regs->msr &= ~MSR_VSX;
msr &= ~MSR_VSX;
#endif
tsk->thread.regs->msr = msr;
}
void giveup_fpu(struct task_struct *tsk)
@ -219,12 +223,16 @@ static int restore_fp(struct task_struct *tsk) { return 0; }
static void __giveup_altivec(struct task_struct *tsk)
{
unsigned long msr;
save_altivec(tsk);
tsk->thread.regs->msr &= ~MSR_VEC;
msr = tsk->thread.regs->msr;
msr &= ~MSR_VEC;
#ifdef CONFIG_VSX
if (cpu_has_feature(CPU_FTR_VSX))
tsk->thread.regs->msr &= ~MSR_VSX;
msr &= ~MSR_VSX;
#endif
tsk->thread.regs->msr = msr;
}
void giveup_altivec(struct task_struct *tsk)