diff options
Diffstat (limited to 'src/cmd/8g/reg.c')
| -rw-r--r-- | src/cmd/8g/reg.c | 146 |
1 files changed, 137 insertions, 9 deletions
diff --git a/src/cmd/8g/reg.c b/src/cmd/8g/reg.c index de5fd87ac..227628226 100644 --- a/src/cmd/8g/reg.c +++ b/src/cmd/8g/reg.c @@ -39,6 +39,8 @@ static int first = 1; +static void fixjmp(Prog*); + Reg* rega(void) { @@ -89,8 +91,8 @@ setoutvar(void) ovar.b[z] |= bit.b[z]; t = structnext(&save); } -//if(bany(b)) -//print("ovars = %Q\n", &ovar); +//if(bany(ovar)) +//print("ovars = %Q\n", ovar); } static void @@ -132,6 +134,8 @@ regopt(Prog *firstp) exregoffset = D_DI; // no externals first = 0; } + + fixjmp(firstp); // count instructions nr = 0; @@ -694,9 +698,9 @@ brk: if(ostats.ndelmov) print(" %4d delmov\n", ostats.ndelmov); if(ostats.nvar) - print(" %4d delmov\n", ostats.nvar); + print(" %4d var\n", ostats.nvar); if(ostats.naddr) - print(" %4d delmov\n", ostats.naddr); + print(" %4d addr\n", ostats.naddr); memset(&ostats, 0, sizeof(ostats)); } @@ -848,10 +852,12 @@ mkvar(Reg *r, Adr *a) } node = a->node; - if(node == N || node->op != ONAME || node->orig != N) + if(node == N || node->op != ONAME || node->orig == N) goto none; node = node->orig; - if(node->sym->name[0] == '.') + if(node->orig != node) + fatal("%D: bad node", a); + if(node->sym == S || node->sym->name[0] == '.') goto none; et = a->etype; o = a->offset; @@ -1095,10 +1101,12 @@ loopit(Reg *r, int32 nr) r1 = rpo2r[i]; me = r1->rpo; d = -1; - if(r1->p1 != R && r1->p1->rpo < me) + // rpo2r[r->rpo] == r protects against considering dead code, + // which has r->rpo == 0. + if(r1->p1 != R && rpo2r[r1->p1->rpo] == r1->p1 && r1->p1->rpo < me) d = r1->p1->rpo; for(r1 = r1->p2; r1 != nil; r1 = r1->p2link) - if(r1->rpo < me) + if(rpo2r[r1->rpo] == r1 && r1->rpo < me) d = rpolca(idom, d, r1->rpo); idom[i] = d; } @@ -1482,7 +1490,7 @@ dumpone(Reg *r) if(bany(&r->refahead)) print(" ra:%Q ", r->refahead); if(bany(&r->calbehind)) - print("cb:%Q ", r->calbehind); + print(" cb:%Q ", r->calbehind); if(bany(&r->calahead)) print(" ca:%Q ", r->calahead); if(bany(&r->regdiff)) @@ -1542,3 +1550,123 @@ noreturn(Prog *p) return 1; return 0; } + +/* + * 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. + */ + +/* what instruction does a JMP to p eventually land on? */ +static Prog* +chasejmp(Prog *p, int *jmploop) +{ + int n; + + n = 0; + while(p != P && p->as == AJMP && p->to.type == D_BRANCH) { + if(++n > 10) { + *jmploop = 1; + break; + } + p = p->to.branch; + } + return p; +} + +/* + * reuse reg pointer for mark/sweep state. + * leave reg==nil at end because alive==nil. + */ +#define alive ((void*)0) +#define dead ((void*)1) + +/* mark all code reachable from firstp as alive */ +static void +mark(Prog *firstp) +{ + Prog *p; + + for(p=firstp; p; p=p->link) { + if(p->reg != dead) + break; + p->reg = alive; + if(p->as != ACALL && p->to.type == D_BRANCH && p->to.branch) + mark(p->to.branch); + if(p->as == AJMP || p->as == ARET || (p->as == ACALL && noreturn(p))) + break; + } +} + +static void +fixjmp(Prog *firstp) +{ + int jmploop; + Prog *p, *last; + + if(debug['R'] && debug['v']) + print("\nfixjmp\n"); + + // pass 1: resolve jump to AJMP, mark all code as dead. + jmploop = 0; + for(p=firstp; p; p=p->link) { + if(debug['R'] && debug['v']) + print("%P\n", p); + if(p->as != ACALL && p->to.type == D_BRANCH && p->to.branch && p->to.branch->as == AJMP) { + p->to.branch = chasejmp(p->to.branch, &jmploop); + if(debug['R'] && debug['v']) + print("->%P\n", p); + } + p->reg = dead; + } + if(debug['R'] && debug['v']) + print("\n"); + + // pass 2: mark all reachable code alive + mark(firstp); + + // pass 3: delete dead code (mostly JMPs). + last = nil; + for(p=firstp; p; p=p->link) { + if(p->reg == dead) { + if(p->link == P && p->as == ARET && last && last->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 %P\n", p); + continue; + } + } + if(last) + last->link = p; + last = p; + } + last->link = P; + + // pass 4: elide JMP to next instruction. + // only safe if there are no jumps to JMPs anymore. + if(!jmploop) { + last = nil; + for(p=firstp; p; p=p->link) { + if(p->as == AJMP && p->to.type == D_BRANCH && p->to.branch == p->link) { + if(debug['R'] && debug['v']) + print("del %P\n", p); + continue; + } + if(last) + last->link = p; + last = p; + } + last->link = P; + } + + if(debug['R'] && debug['v']) { + print("\n"); + for(p=firstp; p; p=p->link) + print("%P\n", p); + print("\n"); + } +} |