diff options
Diffstat (limited to 'src/cmd/6c/reg.c')
| -rw-r--r-- | src/cmd/6c/reg.c | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/src/cmd/6c/reg.c b/src/cmd/6c/reg.c index 996128f75..e40e6c8f0 100644 --- a/src/cmd/6c/reg.c +++ b/src/cmd/6c/reg.c @@ -30,6 +30,8 @@ #include "gc.h" +static void fixjmp(Reg*); + Reg* rega(void) { @@ -185,6 +187,10 @@ regopt(Prog *p) case ACMPL: case ACMPQ: case ACMPW: + case APREFETCHT0: + case APREFETCHT1: + case APREFETCHT2: + case APREFETCHNTA: case ACOMISS: case ACOMISD: case AUCOMISS: @@ -211,6 +217,7 @@ regopt(Prog *p) case AMOVWLZX: case AMOVWQSX: case AMOVWQZX: + case AMOVQL: case AMOVSS: case AMOVSD: @@ -438,6 +445,12 @@ regopt(Prog *p) } /* + * pass 2.1 + * fix jumps + */ + fixjmp(firstr); + + /* * pass 2.5 * find looping structure */ @@ -1384,3 +1397,126 @@ BtoF(int32 b) return 0; return bitno(b) - 16 + FREGMIN; } + +/* what instruction does a JMP to p eventually land on? */ +static Reg* +chasejmp(Reg *r, int *jmploop) +{ + int n; + + n = 0; + for(; r; r=r->s2) { + if(r->prog->as != AJMP || r->prog->to.type != D_BRANCH) + break; + if(++n > 10) { + *jmploop = 1; + break; + } + } + return r; +} + +/* mark all code reachable from firstp as alive */ +static void +mark(Reg *firstr) +{ + Reg *r; + Prog *p; + + for(r=firstr; r; r=r->link) { + if(r->active) + break; + r->active = 1; + p = r->prog; + if(p->as != ACALL && p->to.type == D_BRANCH) + mark(r->s2); + if(p->as == AJMP || p->as == ARET || p->as == AUNDEF) + break; + } +} + +/* + * the code generator depends on being able to write out JMP + * instructions that it can jump to now but fill in later. + * the linker will resolve them nicely, but they make the code + * longer and more difficult to follow during debugging. + * remove them. + */ +static void +fixjmp(Reg *firstr) +{ + int jmploop; + Reg *r; + Prog *p; + + if(debug['R'] && debug['v']) + print("\nfixjmp\n"); + + // pass 1: resolve jump to AJMP, mark all code as dead. + jmploop = 0; + for(r=firstr; r; r=r->link) { + p = r->prog; + if(debug['R'] && debug['v']) + print("%04d %P\n", r->pc, p); + if(p->as != ACALL && p->to.type == D_BRANCH && r->s2 && r->s2->prog->as == AJMP) { + r->s2 = chasejmp(r->s2, &jmploop); + p->to.offset = r->s2->pc; + if(debug['R'] && debug['v']) + print("->%P\n", p); + } + r->active = 0; + } + if(debug['R'] && debug['v']) + print("\n"); + + // pass 2: mark all reachable code alive + mark(firstr); + + // pass 3: delete dead code (mostly JMPs). + for(r=firstr; r; r=r->link) { + if(!r->active) { + p = r->prog; + if(p->link == P && p->as == ARET && r->p1 && r->p1->prog->as != ARET) { + // This is the final ARET, and the code so far doesn't have one. + // Let it stay. + } else { + if(debug['R'] && debug['v']) + print("del %04d %P\n", r->pc, p); + p->as = ANOP; + } + } + } + + // pass 4: elide JMP to next instruction. + // only safe if there are no jumps to JMPs anymore. + if(!jmploop) { + for(r=firstr; r; r=r->link) { + p = r->prog; + if(p->as == AJMP && p->to.type == D_BRANCH && r->s2 == r->link) { + if(debug['R'] && debug['v']) + print("del %04d %P\n", r->pc, p); + p->as = ANOP; + } + } + } + + // fix back pointers. + for(r=firstr; r; r=r->link) { + r->p2 = R; + r->p2link = R; + } + for(r=firstr; r; r=r->link) { + if(r->s2) { + r->p2link = r->s2->p2; + r->s2->p2 = r; + } + } + + if(debug['R'] && debug['v']) { + print("\n"); + for(r=firstr; r; r=r->link) + print("%04d %P\n", r->pc, r->prog); + print("\n"); + } +} + |