124 lines
3 KiB
C
124 lines
3 KiB
C
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#include "mcg.h"
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struct array postorder;
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struct array preorder;
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struct pmap dominators;
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static void recursively_walk_blocks(struct basicblock* bb);
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static void recursively_walk_graph(struct basicblock* bb)
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{
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static ARRAYOF(struct basicblock) pending;
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int i;
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if (array_contains(&postorder, bb) || array_contains(&pending, bb))
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return;
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array_appendu(&preorder, bb);
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array_appendu(&pending, bb);
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i = 0;
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for (i=0; i<bb->nexts.count; i++)
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recursively_walk_graph(bb->nexts.item[i]);
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array_remove(&pending, bb);
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bb->order = postorder.count;
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array_appendu(&postorder, bb);
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}
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static void walk_graph_postorder(struct basicblock* entry)
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{
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int i;
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preorder.count = 0;
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postorder.count = 0;
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recursively_walk_graph(entry);
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for (i=0; i<postorder.count; i++)
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{
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tracef('D', "D: postorder: %s\n",
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((struct basicblock*)postorder.item[i])->name);
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}
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}
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static struct basicblock* intersect(struct basicblock* p1, struct basicblock* p2)
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{
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while (p1 != p2)
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{
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while (p1->order < p2->order)
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p1 = pmap_get(&dominators, p1);
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while (p2->order < p1->order)
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p2 = pmap_get(&dominators, p2);
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}
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return p1;
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}
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void calculate_dominance_graph(struct procedure* proc)
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{
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/* This is the algorithm described here:
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*
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* Cooper, Keith D., Timothy J. Harvey, and Ken Kennedy.
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* "A simple, fast dominance algorithm."
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* Software Practice & Experience 4.1-10 (2001): 1-8.
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*
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* https://www.cs.rice.edu/~keith/EMBED/dom.pdf
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*/
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int i, j;
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bool changed;
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struct basicblock* entry = proc->blocks.item[0];
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entry = proc->blocks.item[0];
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walk_graph_postorder(entry);
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assert(postorder.count == proc->blocks.count);
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dominators.count = 0;
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/* The entry block dominates itself. */
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pmap_put(&dominators, entry, entry);
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do
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{
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changed = false;
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for (i = postorder.count-2; i >= 0; i--)
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{
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struct basicblock* b = postorder.item[i];
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struct basicblock* new_idom = NULL;
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for (j=0; j<b->prevs.count; j++)
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{
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struct basicblock* p = b->prevs.item[j];
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/* Skip unprocessed blocks. */
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if (!pmap_get(&dominators, p))
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continue;
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if (!new_idom)
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new_idom = p;
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else if (pmap_get(&dominators, p))
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new_idom = intersect(p, new_idom);
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}
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if (pmap_get(&dominators, b) != new_idom)
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{
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pmap_put(&dominators, b, new_idom);
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changed = true;
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}
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}
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}
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while (changed);
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for (i=0; i<dominators.count; i++)
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{
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tracef('D', "D: domination: %s -> %s\n",
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((struct basicblock*)dominators.item[i].left)->name,
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((struct basicblock*)dominators.item[i].right)->name);
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}
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}
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/* vim: set sw=4 ts=4 expandtab : */
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