89 lines
1.7 KiB
C
89 lines
1.7 KiB
C
#include "mcg.h"
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static ARRAYOF(struct ir) phis;
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static bool changed;
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static void collect_phis(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* ir = bb->irs.item[i];
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if (ir->opcode == IR_PHI)
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array_append(&phis, ir);
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}
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}
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static bool ir_walker_cb(struct ir* ir, void* user)
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{
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if (ir->left)
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array_remove(&phis, ir->left);
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if (ir->right)
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array_remove(&phis, ir->right);
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return false;
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}
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static void remove_referenced_phis(struct basicblock* bb)
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{
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int i, j;
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for (i=0; i<bb->irs.count; i++)
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{
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struct ir* ir = bb->irs.item[i];
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switch (ir->opcode)
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{
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case IR_PHI:
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for (j=0; j<ir->u.phivalue.count; j++)
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array_remove(&phis, ir->u.phivalue.item[j].right);
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break;
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default:
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ir_walk(ir, ir_walker_cb, NULL);
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break;
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}
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}
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}
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static void purge_unused_phis(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* ir = bb->irs.item[i];
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if ((ir->opcode == IR_PHI) && (array_contains(&phis, ir)))
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{
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array_remove(&bb->irs, ir);
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i--;
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changed = true;
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}
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}
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}
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void pass_remove_dead_phis(void)
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{
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int i;
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do
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{
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changed = false;
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phis.count = 0;
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for (i=0; i<cfg.preorder.count; i++)
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collect_phis(cfg.preorder.item[i]);
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for (i=0; i<cfg.preorder.count; i++)
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remove_referenced_phis(cfg.preorder.item[i]);
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for (i=0; i<cfg.preorder.count; i++)
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purge_unused_phis(cfg.preorder.item[i]);
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}
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while (changed);
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}
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/* vim: set sw=4 ts=4 expandtab : */
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