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Add a pass to do critical edge splitting.

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This commit is contained in:
David Given 2016-10-04 23:42:00 +02:00
parent 8fedf5a0a8
commit ac62c34e19
3 changed files with 115 additions and 5 deletions
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7
mach/proto/mcg/mcg.h
View file

@ -100,13 +100,14 @@ extern void tb_fileend(void);
extern void tb_procedure(struct procedure* proc);
extern void tb_regvar(struct procedure* proc, arith offset, int size, int type, int priority);
extern void pass_convert_locals_to_ssa(struct procedure* proc);
extern void pass_convert_stack_ops(struct procedure* proc);
extern void pass_remove_dead_blocks(struct procedure* proc);
extern void pass_eliminate_trivial_blocks(struct procedure* proc);
extern void pass_group_irs(struct procedure* proc);
extern void pass_instruction_selector(struct procedure* proc);
extern void pass_promote_float_ops(struct procedure* proc);
extern void pass_group_irs(struct procedure* proc);
extern void pass_convert_locals_to_ssa(struct procedure* proc);
extern void pass_remove_dead_blocks(struct procedure* proc);
extern void pass_split_critical_edges(struct procedure* proc);
#endif

91
mach/proto/mcg/pass_splitcriticaledges.c Normal file
View file

@ -0,0 +1,91 @@
#include "mcg.h"
/* Insert empty nodes at certain places in the basic block graph so that when
* we convert out of SSA form, we have somewhere to insert copies. This is
* necessary for correctness in certain circumstances. The best explanation of
* why I've found is here, starting at the bottom of page 23.
*
* Briggs, Preston, et al.
* "Practical improvements to the construction and destruction of static single assignment form."
* Software-Practice and experience 28.8 (1998): 859-882.
*
* http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.25.749
*/
static struct procedure* current_proc;
struct rewrite_params
{
struct basicblock* find;
struct basicblock* replace;
};
static bool find_replace_cb(struct ir* ir, void* user)
{
struct rewrite_params* rwp = user;
if ((ir->opcode == IR_BLOCK) && (ir->u.bvalue == rwp->find))
ir->u.bvalue = rwp->replace;
return false;
}
static void split_edge(struct basicblock* source, struct basicblock* sink)
{
int i;
struct rewrite_params rwp;
struct basicblock* bb = bb_get(NULL);
array_append(&bb->irs,
new_ir1(
IR_JUMP, 0,
new_bbir(sink)
)
);
rwp.find = sink;
rwp.replace = bb;
for (i=0; i<source->irs.count; i++)
ir_walk(source->irs.item[i], find_replace_cb, &rwp);
array_remove(&source->nexts, sink);
array_append(&source->nexts, bb);
array_append(&bb->prevs, source);
array_append(&bb->nexts, sink);
array_remove(&sink->prevs, source);
array_append(&sink->prevs, bb);
array_append(&current_proc->blocks, bb);
}
static void consider_edges_leading_to(struct basicblock* bb)
{
if (bb->prevs.count > 1)
{
int i;
for (i=0; i<bb->prevs.count; i++)
{
struct basicblock* prev = bb->prevs.item[i];
if (prev->nexts.count > 1)
split_edge(prev, bb);
}
}
}
void pass_split_critical_edges(struct procedure* proc)
{
int i;
current_proc = proc;
for (i=0; i<proc->blocks.count; i++)
consider_edges_leading_to(proc->blocks.item[i]);
}
/* vim: set sw=4 ts=4 expandtab : */

22
mach/proto/mcg/procedure.c
View file

@ -15,7 +15,23 @@ static void print_blocks(char k, struct procedure* proc)
bb->is_fake ? "FAKE " : "",
bb->name);
for (int j=0; j<bb->irs.count; j++)
if (bb->prevs.count > 0)
{
tracef(k, "%c: FROM:", k);
for (j=0; j<bb->prevs.count; j++)
tracef(k, " %s", bb->prevs.item[j]->name);
tracef(k, "\n");
}
if (bb->nexts.count > 0)
{
tracef(k, "%c: TO:", k);
for (j=0; j<bb->nexts.count; j++)
tracef(k, " %s", bb->nexts.item[j]->name);
tracef(k, "\n");
}
for (j=0; j<bb->irs.count; j++)
ir_print(k, bb->irs.item[j]);
}
}
@ -40,8 +56,10 @@ void procedure_compile(struct procedure* proc)
print_blocks('3', proc);
pass_convert_locals_to_ssa(proc);
print_blocks('4', proc);
pass_promote_float_ops(proc);
pass_split_critical_edges(proc);
print_blocks('5', proc);
pass_promote_float_ops(proc);
print_blocks('6', proc);
pass_instruction_selector(proc);