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Perform SSA conversion of locals. Much, *much* better code now, at least

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inasmuch as it looks better before register allocation. Basic blocks now know
their own successors and predecessors (after a certain point in the IR
processing).
This commit is contained in:
David Given 2016-10-02 17:50:34 +02:00
parent b11f96e8fe
commit c079e97492
10 changed files with 458 additions and 70 deletions
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6
mach/proto/mcg/basicblock.c
View file

@ -24,7 +24,7 @@ struct basicblock* bb_get(const char* name)
p = str2idf((char*) name, 0);
if (!p->block)
{
p->block = calloc(sizeof(struct basicblock), 1);
p->block = calloc(1, sizeof(*p->block));
p->block->name = name;
}
return p->block;
@ -39,8 +39,4 @@ void bb_alias(struct basicblock* block, const char* name)
p->block = block;
}
void bb_print(char k, struct basicblock* block)
{
}
/* vim: set sw=4 ts=4 expandtab : */

25
mach/proto/mcg/basicblock.h Normal file
View file

@ -0,0 +1,25 @@
#ifndef BASICBLOCK_H
#define BASICBLOCK_H
struct basicblock
{
const char* name;
ARRAYOF(struct em) ems;
ARRAYOF(struct ir) irs;
ARRAYOF(struct hop) hops;
ARRAYOF(struct basicblock) prevs;
ARRAYOF(struct basicblock) nexts;
int order; /* used by SSA code */
bool is_fake : 1;
bool is_root : 1;
bool is_terminated : 1;
};
extern void bb_init(void);
extern struct basicblock* bb_get(const char* name);
extern void bb_alias(struct basicblock* block, const char* name);
#endif

2
mach/proto/mcg/ir.c
View file

@ -107,7 +107,7 @@ static void print_expr(char k, const struct ir* ir)
tracef(k, "%s", ir_data[ir->opcode].name);
if (ir->size)
tracef(k, "%d", ir->size);
tracef(k, ":%d(", ir->id);
tracef(k, "(");
switch (ir->opcode)
{

5
mach/proto/mcg/main.c
View file

@ -5,10 +5,15 @@ bool tracing(char k)
switch (k)
{
case 0: return true;
case 'S': return true;
case 'E': return false;
case 'G': return true;
case '0': return false;
case '1': return false;
case '2': return false;
case '3': return false;
case '4': return false;
case '5': return false;
case 'I': return true;
default: return true;
}

18
mach/proto/mcg/mcg.h
View file

@ -24,6 +24,7 @@
#include "ir.h"
#include "mcgg.h"
#include "hop.h"
#include "basicblock.h"
#include "procedure.h"
extern char em_pseu[][4];
@ -73,17 +74,6 @@ struct em
} u;
};
struct basicblock
{
const char* name;
ARRAYOF(struct em) ems;
ARRAYOF(struct ir) irs;
ARRAYOF(struct hop) hops;
bool is_fake : 1;
bool is_root : 1;
bool is_terminated : 1;
};
extern const char* aprintf(const char* fmt, ...);
extern void tracef(char k, const char* fmt, ...);
extern bool tracing(char k);
@ -104,11 +94,6 @@ extern void data_block(const uint8_t* data, size_t size, bool is_ro);
extern void data_offset(const char* label, arith offset, bool is_ro);
extern void data_bss(arith size, int init);
extern void bb_init(void);
extern struct basicblock* bb_get(const char* name);
extern void bb_alias(struct basicblock* block, const char* name);
extern void bb_print(char k, struct basicblock* block);
extern void tb_filestart(void);
extern void tb_fileend(void);
extern void tb_procedure(struct procedure* proc);
@ -120,6 +105,7 @@ extern void pass_eliminate_trivial_blocks(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);
#endif

38
mach/proto/mcg/pass_convertstackops.c
View file

@ -41,28 +41,6 @@ static struct ir* get_first_pop(struct basicblock* bb)
return NULL;
}
static bool collect_outputs_cb(struct ir* ir, void* user)
{
struct basicblock* caller = user;
if (ir->opcode == IR_BLOCK)
pmap_add(&graph, caller, ir->u.bvalue);
return false;
}
static void make_bb_graph(struct procedure* proc)
{
int i, j;
graph.count = 0;
for (i=0; i<proc->blocks.count; i++)
{
struct basicblock* bb = proc->blocks.item[i];
for (j=0; j<bb->irs.count; j++)
ir_walk(bb->irs.item[j], collect_outputs_cb, bb);
}
}
static void convert_block(struct procedure* proc, struct basicblock* bb)
{
int i, j;
@ -78,11 +56,9 @@ static void convert_block(struct procedure* proc, struct basicblock* bb)
/* Abort unless *every* successor block of this one starts with a pop
* of the same size... */
for (i=0; i<graph.count; i++)
for (i=0; i<bb->nexts.count; i++)
{
if (graph.item[i].left == bb)
{
struct basicblock* outbb = graph.item[i].right;
struct basicblock* outbb = bb->nexts.item[i];
ir = get_first_pop(outbb);
if (!ir || (ir->size != lastpush->size))
@ -92,11 +68,9 @@ static void convert_block(struct procedure* proc, struct basicblock* bb)
/* Also abort unless *every* predecessor block of the one we've
* just found *also* ends in a push of the same size. */
for (j=0; j<graph.count; j++)
for (j=0; j<outbb->prevs.count; j++)
{
if (graph.item[j].right == outbb)
{
struct basicblock* inbb = graph.item[j].left;
struct basicblock* inbb = outbb->prevs.item[j];
ir = get_last_push(inbb);
if (!ir || (ir->size != lastpush->size))
@ -104,8 +78,6 @@ static void convert_block(struct procedure* proc, struct basicblock* bb)
array_appendu(&pushes, ir);
}
}
}
}
/* If we didn't actually find anything, give up. */
@ -139,8 +111,6 @@ void pass_convert_stack_ops(struct procedure* proc)
{
int i;
make_bb_graph(proc);
for (i=0; i<proc->blocks.count; i++)
convert_block(proc, proc->blocks.item[i]);
}

340
mach/proto/mcg/pass_ssa.c Normal file
View file

@ -0,0 +1,340 @@
#include "mcg.h"
static struct basicblock* entry;
static ARRAYOF(struct basicblock) postorder;
static PMAPOF(struct basicblock, struct basicblock) dominators;
static PMAPOF(struct basicblock, struct basicblock) dominancefrontiers;
static struct local* current_local;
static ARRAYOF(struct basicblock) defining;
static ARRAYOF(struct basicblock) needsphis;
static ARRAYOF(struct ir) definitions;
static ARRAYOF(struct basicblock) rewritten;
static void recursively_walk_blocks(struct basicblock* bb);
static void recursively_walk_graph_postorder(struct basicblock* bb)
{
static ARRAYOF(struct basicblock) pending;
int i;
if (array_contains(&postorder, bb) || array_contains(&pending, bb))
return;
array_appendu(&pending, bb);
i = 0;
for (i=0; i<bb->nexts.count; i++)
recursively_walk_graph_postorder(bb->nexts.item[i]);
array_remove(&pending, bb);
bb->order = postorder.count;
array_appendu(&postorder, bb);
}
static void walk_graph_postorder()
{
int i;
postorder.count = 0;
recursively_walk_graph_postorder(entry);
for (i=0; i<postorder.count; i++)
{
tracef('S', "S: postorder: %s\n",
postorder.item[i]->name);
}
}
static struct basicblock* intersect(struct basicblock* p1, struct basicblock* p2)
{
while (p1 != p2)
{
while (p1->order < p2->order)
p1 = pmap_get(&dominators, p1);
while (p2->order < p1->order)
p2 = pmap_get(&dominators, p2);
}
return p1;
}
static void calculate_dominance_graph(void)
{
/* This is the algorithm described here:
*
* Cooper, Keith D., Timothy J. Harvey, and Ken Kennedy.
* "A simple, fast dominance algorithm."
* Software Practice & Experience 4.1-10 (2001): 1-8.
*
* https://www.cs.rice.edu/~keith/EMBED/dom.pdf
*/
int i, j;
bool changed;
dominators.count = 0;
/* The entry block dominates itself. */
pmap_put(&dominators, entry, entry);
do
{
changed = false;
for (i = postorder.count-2; i >= 0; i--)
{
struct basicblock* b = postorder.item[i];
struct basicblock* new_idom = NULL;
for (j=0; j<b->prevs.count; j++)
{
struct basicblock* p = b->prevs.item[j];
if (!new_idom)
new_idom = p;
else if (pmap_get(&dominators, p))
new_idom = intersect(p, new_idom);
}
if (pmap_get(&dominators, b) != new_idom)
{
pmap_put(&dominators, b, new_idom);
changed = true;
}
}
}
while (changed);
for (i=0; i<dominators.count; i++)
{
tracef('S', "S: domination: %s -> %s\n",
dominators.item[i].left->name,
dominators.item[i].right->name);
}
}
static void calculate_dominance_frontier_graph(void)
{
/* This is the algorithm described here:
*
* Cooper, Keith D., Timothy J. Harvey, and Ken Kennedy.
* "A simple, fast dominance algorithm."
* Software Practice & Experience 4.1-10 (2001): 1-8.
*
* https://www.cs.rice.edu/~keith/EMBED/dom.pdf
*/
int i, j;
dominancefrontiers.count = 0;
for (i=0; i<postorder.count; i++)
{
struct basicblock* b = postorder.item[i];
struct basicblock* dominator = pmap_get(&dominators, b);
if (b->prevs.count >= 2)
{
for (j=0; j<b->prevs.count; j++)
{
struct basicblock* runner = b->prevs.item[j];
while (runner != dominator)
{
tracef('S', "S: %s is in %s's dominance frontier\n",
b->name, runner->name);
pmap_add(&dominancefrontiers, runner, b);
runner = pmap_get(&dominators, runner);
}
}
}
}
}
static bool is_local(struct ir* ir)
{
return ((ir->opcode == IR_LOAD) &&
(ir->left->opcode == IR_LOCAL) &&
(ir->left->u.ivalue == current_local->offset));
}
static bool rewrite_loads_cb(struct ir* ir, void* user)
{
struct ir* definition = user;
/* Rewrite in place where possible. */
if (ir->left && is_local(ir->left))
ir->left = definition;
if (ir->right && is_local(ir->right))
ir->right = definition;
/* Otherwise, go via a IR_REG (which should, with luck, turn into no code). */
if (is_local(ir))
{
ir->opcode = IR_NOP;
ir->left = definition;
ir->right = NULL;
}
return false;
}
/* Walks the tree, rewriting IRs to push new definitions downwards. */
static void recursively_rewrite_tree(struct basicblock* bb)
{
int i;
int defcount = definitions.count;
if (array_contains(&rewritten, bb))
return;
array_appendu(&rewritten, bb);
for (i=0; i<bb->irs.count; i++)
{
struct ir* ir = bb->irs.item[i];
if (definitions.count > 0)
{
ir_walk(ir, rewrite_loads_cb, definitions.item[definitions.count-1]);
}
if (((ir->opcode == IR_STORE) &&
(ir->left->opcode == IR_LOCAL) &&
(ir->left->u.ivalue == current_local->offset)
) ||
((i == 0) &&
(ir->opcode == IR_PHI) &&
array_contains(&needsphis, bb)))
{
/* This is a definition. */
if (ir->opcode == IR_STORE)
{
ir->opcode = IR_NOP;
ir->left = ir->right;
ir->right = NULL;
}
array_push(&definitions, ir);
}
}
for (i=0; i<bb->nexts.count; i++)
{
struct basicblock* nextbb = bb->nexts.item[i];
struct ir* ir = nextbb->irs.item[0];
if ((definitions.count > 0) &&
(ir->opcode == IR_PHI) &&
array_contains(&needsphis, nextbb))
{
array_appendu(&ir->u.phivalue, definitions.item[definitions.count-1]);
}
recursively_rewrite_tree(nextbb);
}
definitions.count = defcount;
}
static void ssa_convert(void)
{
int i, j;
/* If this is a parameter, synthesise a load/store at the beginning of the
* program to force it into a register. (Unless it's written to it'll
* always be read from the frame.) */
if (current_local->offset >= 0)
{
struct ir* ir = new_ir2(
IR_STORE, current_local->size,
new_localir(current_local->offset),
new_ir1(
IR_LOAD, current_local->size,
new_localir(current_local->offset)
)
);
ir->root = ir;
ir->left->root = ir;
ir->right->root = ir;
ir->right->left->root = ir;
array_insert(&entry->irs, ir, 0);
}
defining.count = 0;
needsphis.count = 0;
/* Find everwhere where the variable is *defined*. */
for (i=0; i<postorder.count; i++)
{
struct basicblock* bb = postorder.item[i];
for (j=0; j<bb->irs.count; j++)
{
struct ir* ir = bb->irs.item[j];
if ((ir->opcode == IR_STORE) &&
(ir->left->opcode == IR_LOCAL) &&
(ir->left->u.ivalue == current_local->offset))
{
array_appendu(&defining, bb);
}
}
}
/* Every block which is in one of the defining block's dominance frontiers
* requires a phi. Remember that adding a phi also adds a definition. */
for (i=0; i<defining.count; i++)
{
struct basicblock* bb = defining.item[i];
struct basicblock* dominates = pmap_get(&dominancefrontiers, bb);
if (dominates)
{
array_appendu(&needsphis, dominates);
array_appendu(&defining, dominates);
tracef('S', "S: local %d needs phi in block %s\n", current_local->offset, dominates->name);
}
}
/* Add empty phi nodes. */
for (i=0; i<needsphis.count; i++)
{
struct basicblock* bb = needsphis.item[i];
struct ir* ir = new_ir0(IR_PHI, current_local->size);
ir->root = ir;
array_insert(&bb->irs, ir, 0);
}
/* Now do the rewriting by walking the tree, pushing definitions down the tree. */
definitions.count = 0;
rewritten.count = 0;
recursively_rewrite_tree(entry);
}
void pass_convert_locals_to_ssa(struct procedure* proc)
{
int i;
entry = proc->blocks.item[0];
walk_graph_postorder();
assert(postorder.count == proc->blocks.count);
calculate_dominance_graph();
calculate_dominance_frontier_graph();
for (i=0; i<proc->locals.count; i++)
{
current_local = proc->locals.item[i].right;
if (current_local->is_register)
ssa_convert();
}
}
/* vim: set sw=4 ts=4 expandtab : */

56
mach/proto/mcg/procedure.c
View file

@ -27,15 +27,67 @@ void procedure_compile(struct procedure* proc)
print_blocks('1', proc);
pass_group_irs(proc);
/* Passes from here on must preserve IR grouping */
pass_eliminate_trivial_blocks(proc);
pass_remove_dead_blocks(proc);
pass_convert_stack_ops(proc);
pass_promote_float_ops(proc);
procedure_update_bb_graph(proc);
/* Passes from here on can't alter the BB graph */
print_blocks('2', proc);
pass_convert_stack_ops(proc);
print_blocks('3', proc);
pass_convert_locals_to_ssa(proc);
print_blocks('4', proc);
pass_promote_float_ops(proc);
print_blocks('5', proc);
pass_instruction_selector(proc);
}
static bool collect_outputs_cb(struct ir* ir, void* user)
{
struct basicblock* caller = user;
if (ir->opcode == IR_BLOCK)
{
array_appendu(&caller->nexts, ir->u.bvalue);
array_appendu(&ir->u.bvalue->prevs, caller);
}
return false;
}
void procedure_update_bb_graph(struct procedure* proc)
{
int i, j;
for (i=0; i<proc->blocks.count; i++)
{
struct basicblock* bb = proc->blocks.item[i];
bb->prevs.count = bb->nexts.count = 0;
}
for (i=0; i<proc->blocks.count; i++)
{
struct basicblock* bb = proc->blocks.item[i];
for (j=0; j<bb->irs.count; j++)
ir_walk(bb->irs.item[j], collect_outputs_cb, bb);
}
for (i=0; i<proc->blocks.count; i++)
{
struct basicblock* bb = proc->blocks.item[i];
for (j=0; j<bb->nexts.count; j++)
{
tracef('G', "G: graph %s -> %s\n",
bb->name,
bb->nexts.item[j]->name);
}
}
}
/* vim: set sw=4 ts=4 expandtab : */

13
mach/proto/mcg/table
View file

@ -39,6 +39,7 @@ PATTERNS
int;
float;
any;
PAIR(BLOCK4, BLOCK4);
@ -69,6 +70,13 @@ PATTERNS
prefers int(in)
cost 1;
int = NOP4(in:int)
emit "mov %int, %in"
cost 1;
any = PHI4
cost 0;
float = in:REG4
prefers float(in)
cost 1;
@ -146,6 +154,11 @@ PATTERNS
emit "b $false"
cost 8;
CJUMPLT(value:cc, PAIR(true:BLOCK4, false:BLOCK4))
emit "blt $true"
emit "b $false"
cost 8;
CALL(dest:LABEL4)
emit "bl $dest"
cost 4;

1
util/mcgg/ir.dat
View file

@ -6,6 +6,7 @@
S CONST # must be followed by float form
S CONSTF
S REG
S NOP
S LABEL
S BLOCK
V PAIR