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gh-87092: in compiler, move the detection of exception handlers before the CFG optimization stage #96935

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merged 8 commits into from
Sep 20, 2022
Merged

gh-87092: in compiler, move the detection of exception handlers before the CFG optimization stage #96935

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ba5e556
add b_except_handler, calculated seprately from reachability
iritkatriel Sep 12, 2022
a5bef75
remove b_except_predecessors
iritkatriel Sep 13, 2022
dd2b3f3
move mark_except_handler to before cfg optimizations
iritkatriel Sep 13, 2022
d5ab812
move label_exception_targets to before cfg optimizations
iritkatriel Sep 13, 2022
497c8aa
Merge remote-tracking branch 'upstream/main' into resolve-exceptions-…
iritkatriel Sep 19, 2022
a3b4a33
typo in comment
iritkatriel Sep 20, 2022
afbad11
Merge remote-tracking branch 'upstream/main' into resolve-exceptions-…
iritkatriel Sep 20, 2022
2802145
asserts under #ifndef NDEBUG
iritkatriel Sep 20, 2022
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44 changes: 29 additions & 15 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -260,8 +260,6 @@ typedef struct basicblock_ {
int b_ialloc;
/* Number of predecssors that a block has. */
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int b_predecessors;
/* Number of predecssors that a block has as an exception handler. */
int b_except_predecessors;
/* depth of stack upon entry of block, computed by stackdepth() */
int b_startdepth;
/* instruction offset for block, computed by assemble_jump_offsets() */
Expand All @@ -270,6 +268,8 @@ typedef struct basicblock_ {
unsigned b_preserve_lasti : 1;
/* Used by compiler passes to mark whether they have visited a basic block. */
unsigned b_visited : 1;
/* b_except_handler is used by the cold-detection algorithm to mark exception targets */
unsigned b_except_handler : 1;
/* b_cold is true if this block is not perf critical (like an exception handler) */
unsigned b_cold : 1;
/* b_warm is used by the cold-detection algorithm to mark blocks which are definitely not cold */
Expand Down Expand Up @@ -7296,6 +7296,23 @@ label_exception_targets(basicblock *entryblock) {
return -1;
}


static int
mark_except_handlers(basicblock *entryblock) {
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
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assert(!b->b_except_handler);
}
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
for (int i=0; i < b->b_iused; i++) {
struct instr *instr = &b->b_instr[i];
if (is_block_push(instr)) {
instr->i_target->b_except_handler = 1;
}
}
}
return 0;
}

static int
mark_warm(basicblock *entryblock) {
basicblock **stack = make_cfg_traversal_stack(entryblock);
Expand All @@ -7308,7 +7325,7 @@ mark_warm(basicblock *entryblock) {
entryblock->b_visited = 1;
while (sp > stack) {
basicblock *b = *(--sp);
assert(!b->b_except_predecessors);
assert(!b->b_except_handler);
b->b_warm = 1;
basicblock *next = b->b_next;
if (next && BB_HAS_FALLTHROUGH(b) && !next->b_visited) {
Expand Down Expand Up @@ -7343,8 +7360,7 @@ mark_cold(basicblock *entryblock) {

basicblock **sp = stack;
for (basicblock *b = entryblock; b != NULL; b = b->b_next) {
if (b->b_except_predecessors) {
assert(b->b_except_predecessors == b->b_predecessors);
if (b->b_except_handler) {
assert(!b->b_warm);
*sp++ = b;
b->b_visited = 1;
Expand Down Expand Up @@ -8257,8 +8273,8 @@ static void
dump_basicblock(const basicblock *b)
{
const char *b_return = basicblock_returns(b) ? "return " : "";
fprintf(stderr, "%d: [%d %d %d %p] used: %d, depth: %d, offset: %d %s\n",
b->b_label, b->b_cold, b->b_warm, BB_NO_FALLTHROUGH(b), b, b->b_iused,
fprintf(stderr, "%d: [EH=%d CLD=%d WRM=%d NO_FT=%d %p] used: %d, depth: %d, offset: %d %s\n",
b->b_label, b->b_except_handler, b->b_cold, b->b_warm, BB_NO_FALLTHROUGH(b), b, b->b_iused,
b->b_startdepth, b->b_offset, b_return);
if (b->b_instr) {
int i;
Expand Down Expand Up @@ -8616,6 +8632,12 @@ assemble(struct compiler *c, int addNone)
if (calculate_jump_targets(g->g_entryblock)) {
goto error;
}
if (mark_except_handlers(g->g_entryblock) < 0) {
goto error;
}
if (label_exception_targets(g->g_entryblock)) {
goto error;
}
if (optimize_cfg(g, consts, c->c_const_cache)) {
goto error;
}
Expand All @@ -8634,9 +8656,6 @@ assemble(struct compiler *c, int addNone)
}
/* TO DO -- For 3.12, make sure that `maxdepth <= MAX_ALLOWED_STACK_USE` */

if (label_exception_targets(g->g_entryblock)) {
goto error;
}
convert_exception_handlers_to_nops(g->g_entryblock);

if (push_cold_blocks_to_end(g, code_flags) < 0) {
Expand Down Expand Up @@ -9353,11 +9372,6 @@ mark_reachable(basicblock *entryblock) {
*sp++ = target;
}
target->b_predecessors++;
if (is_block_push(instr)) {
target->b_except_predecessors++;
}
assert(target->b_except_predecessors == 0 ||
target->b_except_predecessors == target->b_predecessors);
}
}
}
Expand Down