Hi Michael, On Mon, May 28, 2018 at 09:59:29PM +1000, Michael Ellerman wrote: > Hi Simon, > > wei.guo.si...@gmail.com writes: > > diff --git a/arch/powerpc/lib/memcmp_64.S b/arch/powerpc/lib/memcmp_64.S > > index f20e883..4ba7bb6 100644 > > --- a/arch/powerpc/lib/memcmp_64.S > > +++ b/arch/powerpc/lib/memcmp_64.S > > @@ -174,6 +235,13 @@ _GLOBAL(memcmp) > > blr > > > > .Llong: > > +#ifdef CONFIG_ALTIVEC > > + /* Try to use vmx loop if length is equal or greater than 4K */ > > + cmpldi cr6,r5,VMX_THRESH > > + bge cr6,.Lsameoffset_vmx_cmp > > + > > Here we decide to use vmx, but we don't do any CPU feature checks. > > > > @@ -332,7 +400,94 @@ _GLOBAL(memcmp) > > 8: > > blr > > > > +#ifdef CONFIG_ALTIVEC > > +.Lsameoffset_vmx_cmp: > > + /* Enter with src/dst addrs has the same offset with 8 bytes > > + * align boundary > > + */ > > + ENTER_VMX_OPS > > + beq cr1,.Llong_novmx_cmp > > + > > +3: > > + /* need to check whether r4 has the same offset with r3 > > + * for 16 bytes boundary. > > + */ > > + xor r0,r3,r4 > > + andi. r0,r0,0xf > > + bne .Ldiffoffset_vmx_cmp_start > > + > > + /* len is no less than 4KB. Need to align with 16 bytes further. > > + */ > > + andi. rA,r3,8 > > + LD rA,0,r3 > > + beq 4f > > + LD rB,0,r4 > > + cmpld cr0,rA,rB > > + addi r3,r3,8 > > + addi r4,r4,8 > > + addi r5,r5,-8 > > + > > + beq cr0,4f > > + /* save and restore cr0 */ > > + mfocrf r5,64 > > + EXIT_VMX_OPS > > + mtocrf 64,r5 > > + b .LcmpAB_lightweight > > + > > +4: > > + /* compare 32 bytes for each loop */ > > + srdi r0,r5,5 > > + mtctr r0 > > + clrldi r5,r5,59 > > + li off16,16 > > + > > +.balign 16 > > +5: > > + lvx v0,0,r3 > > + lvx v1,0,r4 > > + vcmpequd. v0,v0,v1 > > vcmpequd is only available on Power8 and later CPUs. > > Which means this will crash on Power7 or earlier. > > Something like this should fix it I think. > > diff --git a/arch/powerpc/lib/memcmp_64.S b/arch/powerpc/lib/memcmp_64.S > index 96eb08b2be2e..0a11ff14dcd9 100644 > --- a/arch/powerpc/lib/memcmp_64.S > +++ b/arch/powerpc/lib/memcmp_64.S > @@ -236,9 +236,11 @@ _GLOBAL(memcmp) > > .Llong: > #ifdef CONFIG_ALTIVEC > +BEGIN_FTR_SECTION > /* Try to use vmx loop if length is equal or greater than 4K */ > cmpldi cr6,r5,VMX_THRESH > bge cr6,.Lsameoffset_vmx_cmp > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) > > .Llong_novmx_cmp: > #endif Thanks for the good catch! I will update that. > > > There's another problem which is that old toolchains don't know about > vcmpequd. To fix that we'll need to add a macro that uses .long to > construct the instruction. Right. I will add the corresponding macros.
Thanks for your review. BR, - Simon
