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S390: Optimize __memset_z196.
It turned out that an 256b-mvc instruction which depends on the result of a previous 256b-mvc instruction is counterproductive. Therefore this patch adjusts the 256b-loop by storing the first byte with stc and setting the remaining 255b with mvc. Now the 255b-mvc instruction depends on the stc instruction.
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@ -157,28 +157,27 @@ ENTRY(MEMSET_Z196)
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# if !defined __s390x__
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llgfr %r4,%r4
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# endif /* !defined __s390x__ */
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ltgr %r4,%r4
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je .L_Z196_4
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clgfi %r4,1
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jl .L_Z196_4 # n == 0
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stc %r3,0(%r2)
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je .L_Z196_4 # n == 1
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aghi %r4,-2
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lgr %r1,%r2
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cghi %r4,1
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je .L_Z196_4
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aghi %r4,-2
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srlg %r5,%r4,8
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ltgr %r5,%r5
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jne .L_Z196_1
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risbg %r5,%r4,8,128+63,56 # r5 = n / 256
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jne .L_Z196_1 # Jump away if r5 != 0
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.L_Z196_3:
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exrl %r4,.L_Z196_17
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.L_Z196_4:
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br %r14
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.L_Z196_1:
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cgfi %r5,1048576
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jh __memset_mvcle # Switch to mvcle for >256MB
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jh __memset_mvcle # Switch to mvcle for >256MB
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.L_Z196_2:
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pfd 2,1024(%r1)
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mvc 1(256,%r1),0(%r1)
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mvc 1(255,%r1),0(%r1)
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aghi %r5,-1
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la %r1,256(%r1)
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stc %r3,0(%r1)
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jne .L_Z196_2
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j .L_Z196_3
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.L_Z196_17:
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