diff options
Diffstat (limited to 'src/cmd/8g/peep.c')
| -rw-r--r-- | src/cmd/8g/peep.c | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/src/cmd/8g/peep.c b/src/cmd/8g/peep.c index 580b1a922..5ad29e1b2 100644 --- a/src/cmd/8g/peep.c +++ b/src/cmd/8g/peep.c @@ -120,6 +120,25 @@ peep(void) p = p->link; } } + + // movb elimination. + // movb is simulated by the linker + // when a register other than ax, bx, cx, dx + // is used, so rewrite to other instructions + // when possible. a movb into a register + // can smash the entire 32-bit register without + // causing any trouble. + for(r=firstr; r!=R; r=r->link) { + p = r->prog; + if(p->as == AMOVB && regtyp(&p->to)) { + // movb into register. + // from another register or constant can be movl. + if(regtyp(&p->from) || p->from.type == D_CONST) + p->as = AMOVL; + else + p->as = AMOVBLZX; + } + } // constant propagation // find MOV $con,R followed by @@ -152,6 +171,8 @@ loop1: for(r=firstr; r!=R; r=r->link) { p = r->prog; switch(p->as) { + case AMOVB: + case AMOVW: case AMOVL: if(regtyp(&p->to)) if(regtyp(&p->from)) { @@ -182,6 +203,7 @@ loop1: } break; + case AADDB: case AADDL: case AADDW: if(p->from.type != D_CONST || needc(p->link)) @@ -204,6 +226,7 @@ loop1: } break; + case ASUBB: case ASUBL: case ASUBW: if(p->from.type != D_CONST || needc(p->link)) @@ -380,6 +403,8 @@ subprop(Reg *r0) case AMOVSL: return 0; + case AMOVB: + case AMOVW: case AMOVL: if(p->to.type == v1->type) goto gotit; @@ -560,6 +585,8 @@ copyu(Prog *p, Adr *v, Adr *s) case ANOP: /* rhs store */ + case AMOVB: + case AMOVW: case AMOVL: case AMOVBLSX: case AMOVBLZX: @@ -624,8 +651,6 @@ copyu(Prog *p, Adr *v, Adr *s) case AXORB: case AXORL: case AXORW: - case AMOVB: - case AMOVW: if(copyas(&p->to, v)) return 2; goto caseread; |