cmd/5g: peep.c: reactivate some optimisations

Thanks to Minux and Remy for their advice.

The EOR optimisation is applied to a few places in the stdlib.

// hash/crc32/crc32.go
func update(crc uint32, tab *Table, p []byte) uint32 {
	crc = ^crc
	for _, v := range p {
        	crc = tab[byte(crc)^v] ^ (crc >> 8)
	}
	return ^crc
}

before:

--- prog list "update" ---
0164 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:101) TEXT        update+0(SB),$12-24
0165 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:101) MOVW        tab+4(FP),R8
0166 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:102) MOVW        crc+0(FP),R0
0167 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:102) EOR         $-1,R0,R5
0168 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:103) MOVW        p+8(FP),R0
0169 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:103) MOVW        R0,autotmp_0019+-12(SP)

after:

--- prog list "update" ---
0164 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:101) TEXT        update+0(SB),$12-24
0165 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:101) MOVW        tab+4(FP),R8
0166 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:102) MOVW        crc+0(FP),R0
0167 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:102) MVN         R0,R5
0168 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:103) MOVW        p+8(FP),R0
0169 (/home/dfc/go/src/pkg/hash/crc32/crc32.go:103) MOVW        R0,autotmp_0019+-12(SP)

After 5l has done its work,

        crc = ^crc
   3d710:       e59d0014        ldr     r0, [sp, #20]
   3d714:       e3e0b000        mvn     fp, #0
   3d718:       e020500b        eor     r5, r0, fp

becomes

        crc = ^crc
   3d710:       e59d0014        ldr     r0, [sp, #20]
   3d714:       e1e05000        mvn     r5, r0

The MOVB optimisation has a small impact on the stdlib, in strconv
and gzip.

// GZIP (RFC 1952) is little-endian, unlike ZLIB (RFC 1950).
func put2(p []byte, v uint16) {
        p[0] = uint8(v >> 0)
        p[1] = uint8(v >> 8)
}

before:

--- prog list "put2" ---
1369 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:76) TEXT       put2+0(SB),$0-16
1370 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:76) MOVHU      v+12(FP),R4
1371 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVHU      R4,R0
1372 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVHU      R0,R0
1373 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVBU      R0,R1
1374 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVBU      R1,R3
1375 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVW       $p+0(FP),R1

after:

--- prog list "put2" ---
1369 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:76) TEXT       put2+0(SB),$0-16
1370 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:76) MOVHU      v+12(FP),R4
1371 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVHU      R4,R0
1372 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVBU      R0,R1
1373 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVBU      R1,R3
1374 (/home/dfc/go/src/pkg/compress/gzip/gzip.go:77) MOVW       $p+0(FP),R1

R=remyoudompheng, rsc, minux.ma
CC=golang-dev
https://golang.org/cl/6674048

diff --git a/src/cmd/5g/peep.c b/src/cmd/5g/peep.c
index 75c691c150a906d66160e0761bfa080b903e3847..f9d3dcd348deef65d986da334355379b6d4f7d21 100644 (file)
--- a/src/cmd/5g/peep.c
+++ b/src/cmd/5g/peep.c
@@ -133,26 +133,24 @@ loop1:
        if(t)
                goto loop1;
 
-return;
 
-#ifdef NOTDEF
        for(r=firstr; r!=R; r=r->link) {
                p = r->prog;
                switch(p->as) {
-//             case AEOR:
-//                     /*
-//                      * EOR -1,x,y => MVN x,y
-//                      */
-//                     if(isdconst(&p->from) && p->from.offset == -1) {
-//                             p->as = AMVN;
-//                             p->from.type = D_REG;
-//                             if(p->reg != NREG)
-//                                     p->from.reg = p->reg;
-//                             else
-//                                     p->from.reg = p->to.reg;
-//                             p->reg = NREG;
-//                     }
-//                     break;
+               case AEOR:
+                       /*
+                        * EOR -1,x,y => MVN x,y
+                        */
+                       if(isdconst(&p->from) && p->from.offset == -1) {
+                               p->as = AMVN;
+                               p->from.type = D_REG;
+                               if(p->reg != NREG)
+                                       p->from.reg = p->reg;
+                               else
+                                       p->from.reg = p->to.reg;
+                               p->reg = NREG;
+                       }
+                       break;
 
                case AMOVH:
                case AMOVHU:
@@ -161,6 +159,7 @@ return;
                        /*
                         * look for MOVB x,R; MOVB R,R
                         */
+                       r1 = r->link;
                        if(p->to.type != D_REG)
                                break;
                        if(r1 == R)
@@ -175,8 +174,8 @@ return;
                        excise(r1);
                        break;
                }
-               r1 = r->link;
        }
+#ifdef NOTDEF
 
 //     for(r=firstr; r!=R; r=r->link) {
 //             p = r->prog;