135 lines
3.3 KiB
C
135 lines
3.3 KiB
C
#include "mcg.h"
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static PMAPOF(struct basicblock, struct ir) pops;
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static PMAPOF(struct basicblock, struct ir) pushes;
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static struct ir* get_last_push(struct basicblock* bb)
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{
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int i;
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for (i=bb->irs.count-1; i>=0; i--)
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{
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struct ir* ir = bb->irs.item[i];
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if (ir->opcode == IR_PUSH)
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return ir;
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if (ir_find(ir, IR_POP))
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return NULL;
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}
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return NULL;
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}
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static struct ir* get_first_pop(struct basicblock* bb)
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{
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int i;
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for (i=0; i<bb->irs.count; i++)
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{
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struct ir* irr;
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struct ir* ir = bb->irs.item[i];
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if (ir->opcode == IR_PUSH)
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return NULL;
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irr = ir_find(ir, IR_POP);
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if (irr)
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return irr;
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}
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return NULL;
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}
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static void convert_block(struct basicblock* bb)
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{
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int i, j;
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struct ir* ir;
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pushes.count = pops.count = 0;
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for (;;)
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{
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struct ir* lastpush = get_last_push(bb);
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if (!lastpush)
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return;
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/* Abort unless *every* successor block of this one starts with a pop
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* of the same size... */
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for (i=0; i<bb->nexts.count; i++)
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{
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struct basicblock* outbb = bb->nexts.item[i];
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ir = get_first_pop(outbb);
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if (!ir || (ir->size != lastpush->size))
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return;
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pmap_add(&pops, outbb, ir);
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/* Also abort unless *every* predecessor block of the one we've
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* just found *also* ends in a push of the same size. */
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for (j=0; j<outbb->prevs.count; j++)
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{
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struct basicblock* inbb = outbb->prevs.item[j];
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ir = get_last_push(inbb);
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if (!ir || (ir->size != lastpush->size))
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return;
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pmap_add(&pushes, inbb, ir);
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}
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}
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/* If we didn't actually find anything, give up. */
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if ((pushes.count == 0) || (pops.count == 0))
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return;
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/* Okay, now we can wire them all up. */
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for (i=0; i<pushes.count; i++)
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{
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struct ir* ir = pushes.item[i].right;
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ir->opcode = IR_NOP;
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}
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for (i=0; i<pops.count; i++)
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{
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struct basicblock* outbb = pops.item[i].left;
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struct ir* ir = pops.item[i].right;
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assert(pushes.count > 0);
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if (pushes.count == 1)
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{
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/* The push happened in exactly one place; that means we don't need a phi and can
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* just import the value directly. */
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struct ir* src = pushes.item[0].right;
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ir->opcode = IR_NOP;
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ir->left = src;
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}
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else
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{
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/* The push could have happened in one of several places; we need a phi. */
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struct ir* phi = new_ir0(IR_PHI, ir->size);
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for (j=0; j<pushes.count; j++)
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{
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pmap_add(&phi->u.phivalue,
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pushes.item[j].left,
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pushes.item[j].right);
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}
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phi->root = phi;
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*ir = *phi;
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}
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}
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}
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}
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void pass_convert_stack_ops(void)
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{
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int i;
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for (i=0; i<cfg.preorder.count; i++)
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convert_block(cfg.preorder.item[i]);
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}
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/* vim: set sw=4 ts=4 expandtab : */
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