diff options
Diffstat (limited to 'src/cmd/8c/reg.c')
| -rw-r--r-- | src/cmd/8c/reg.c | 151 |
1 files changed, 150 insertions, 1 deletions
diff --git a/src/cmd/8c/reg.c b/src/cmd/8c/reg.c index 6ba07bed2..6c87d70a5 100644 --- a/src/cmd/8c/reg.c +++ b/src/cmd/8c/reg.c @@ -30,6 +30,8 @@ #include "gc.h" +static void fixjmp(Reg*); + Reg* rega(void) { @@ -148,7 +150,6 @@ regopt(Prog *p) r->p1 = R; r1->s1 = R; } - bit = mkvar(r, &p->from); if(bany(&bit)) switch(p->as) { @@ -182,6 +183,10 @@ regopt(Prog *p) case ACMPB: case ACMPL: case ACMPW: + case APREFETCHT0: + case APREFETCHT1: + case APREFETCHT2: + case APREFETCHNTA: for(z=0; z<BITS; z++) r->use2.b[z] |= bit.b[z]; break; @@ -372,6 +377,12 @@ regopt(Prog *p) } /* + * pass 2.1 + * fix jumps + */ + fixjmp(firstr); + + /* * pass 2.5 * find looping structure */ @@ -543,6 +554,13 @@ brk: if(!debug['R'] || debug['P']) peep(); + if(debug['R'] && debug['v']) { + print("after pass 7 (peep)\n"); + for(r=firstr; r; r=r->link) + print("%04d %P\n", r->pc, r->prog); + print("\n"); + } + /* * pass 8 * recalculate pc @@ -596,6 +614,14 @@ brk: while(p->link && p->link->as == ANOP) p->link = p->link->link; } + + if(debug['R'] && debug['v']) { + print("after pass 8 (fixup pc)\n"); + for(p1=firstr->prog; p1!=P; p1=p1->link) + print("%P\n", p1); + print("\n"); + } + if(r1 != R) { r1->link = freer; freer = firstr; @@ -1285,3 +1311,126 @@ BtoR(int32 b) return 0; return bitno(b) + D_AX; } + +/* 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"); + } +} + |