9456200d91
This might not be a good idea, the problem was that many spurious registers would be added to the Bits data-structures during compilation (and would always remain 0). However, doing the above modification de-uniformizes the handling of temps and regs, this makes the code longer and not really nicer. Also, additional Bits structures are required to track the registers independently. Overall this might be a bad idea to revert.
103 lines
1.9 KiB
C
103 lines
1.9 KiB
C
#include "lisc.h"
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/* For x86_64, we have to:
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*
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* - check that constants are used only in
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* places allowed by the machine
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*
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* - explicit machine register contraints
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* on instructions like division.
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*
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* - lower calls (future, I have to think
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* about their representation and the
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* way I deal with structs/unions in the
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* ABI)
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*/
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extern Ins insb[NIns], *curi; /* shared work buffer */
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static void
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emit(short op, Ref to, Ref arg0, Ref arg1)
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{
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if (curi == insb)
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diag("isel: too many instructions");
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*--curi = (Ins){op, to, {arg0, arg1}};
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}
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static int
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newtmp(int type, Fn *fn)
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{
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static int n;
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int t;
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t = fn->ntmp++;
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fn->tmp = realloc(fn->tmp, fn->ntmp * sizeof fn->tmp[0]);
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if (!fn->tmp)
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diag("isel: out of memory");
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fn->tmp[t] = (Tmp){.type = type};
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sprintf(fn->tmp[t].name, "isel%d", ++n);
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return t;
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}
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static void
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sel(Ins *i, Fn *fn)
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{
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int t;
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Ref r0, r1;
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switch (i->op) {
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case ODiv:
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r0 = REG(RAX);
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r1 = REG(RDX);
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if (0) {
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case ORem:
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r0 = REG(RDX);
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r1 = REG(RAX);
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}
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emit(OCopy, i->to, r0, R);
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emit(OCopy, R, r1, R);
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if (rtype(i->arg[1]) == RCon) {
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/* immediates not allowed for
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* divisions in x86
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*/
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t = newtmp(fn->tmp[i->to.val].type, fn);
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r0 = TMP(t);
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} else
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r0 = i->arg[1];
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emit(OXDiv, R, r0, R);
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emit(OSign, REG(RDX), REG(RAX), R);
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emit(OCopy, REG(RAX), i->arg[0], R);
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if (rtype(i->arg[1]) == RCon)
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emit(OCopy, r0, i->arg[1], R);
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break;
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case OAdd:
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case OSub:
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case OCopy:
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emit(i->op, i->to, i->arg[0], i->arg[1]);
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break;
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default:
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diag("isel: non-exhaustive implementation");
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}
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}
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/* instruction selection
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*/
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void
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isel(Fn *fn)
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{
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Blk *b;
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Ins *i;
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uint nins;
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for (b=fn->start; b; b=b->link) {
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curi = &insb[NIns];
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for (i=&b->ins[b->nins]; i!=b->ins;) {
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sel(--i, fn);
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}
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nins = &insb[NIns] - curi;
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free(b->ins);
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b->ins = alloc(nins * sizeof b->ins[0]);
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memcpy(b->ins, curi, nins * sizeof b->ins[0]);
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b->nins = nins;
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}
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}
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