summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--src/asm2wasm.h1
-rw-r--r--src/passes/RemoveUnusedBrs.cpp67
-rw-r--r--test/emcc_hello_world.fromasm17
-rw-r--r--test/emcc_hello_world.fromasm.clamp17
-rw-r--r--test/emcc_hello_world.fromasm.imprecise17
-rw-r--r--test/memorygrowth.fromasm13
-rw-r--r--test/memorygrowth.fromasm.clamp13
-rw-r--r--test/memorygrowth.fromasm.imprecise13
-rw-r--r--test/passes/bysyncify_optimize-level=1.txt11
-rw-r--r--test/passes/remove-unused-brs.txt51
-rw-r--r--test/passes/remove-unused-brs.wast48
-rw-r--r--test/unit.fromasm24
-rw-r--r--test/unit.fromasm.clamp24
-rw-r--r--test/unit.fromasm.imprecise24
14 files changed, 250 insertions, 90 deletions
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 015c43053..d4b4f8674 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -1688,6 +1688,7 @@ void Asm2WasmBuilder::processAsm(Ref ast) {
// autodrop can add some garbage
passRunner.add("vacuum");
passRunner.add("remove-unused-brs");
+ passRunner.add("vacuum");
passRunner.add("remove-unused-names");
passRunner.add("merge-blocks");
passRunner.add("optimize-instructions");
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index 1e67ecec3..7f3a9965d 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -21,6 +21,7 @@
#include <ir/branch-utils.h>
#include <ir/cost.h>
#include <ir/effects.h>
+#include <ir/literal-utils.h>
#include <ir/utils.h>
#include <parsing.h>
#include <pass.h>
@@ -49,6 +50,23 @@ static bool canTurnIfIntoBrIf(Expression* ifCondition,
return !EffectAnalyzer(options, ifCondition).invalidates(value);
}
+// Check if it is not worth it to run code unconditionally. This
+// assumes we are trying to run two expressions where previously
+// only one of the two might have executed. We assume here that
+// executing both is good for code size.
+static bool tooCostlyToRunUnconditionally(const PassOptions& passOptions,
+ Expression* one,
+ Expression* two) {
+ // If we care mostly about code size, just do it for that reason.
+ if (passOptions.shrinkLevel) {
+ return false;
+ }
+ // Consider the cost of executing all the code unconditionally.
+ const auto TOO_MUCH = 7;
+ auto total = CostAnalyzer(one).cost + CostAnalyzer(two).cost;
+ return total >= TOO_MUCH;
+}
+
struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> {
bool isFunctionParallel() override { return true; }
@@ -283,12 +301,40 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> {
void visitIf(If* curr) {
if (!curr->ifFalse) {
- // if without an else. try to reduce if (condition) br => br_if
- // (condition)
- Break* br = curr->ifTrue->dynCast<Break>();
- if (br && !br->condition) { // TODO: if there is a condition, join them
+ // if without an else. try to reduce
+ // if (condition) br => br_if (condition)
+ if (Break* br = curr->ifTrue->dynCast<Break>()) {
if (canTurnIfIntoBrIf(curr->condition, br->value, getPassOptions())) {
- br->condition = curr->condition;
+ if (!br->condition) {
+ br->condition = curr->condition;
+ } else {
+ // In this case we can replace
+ // if (condition1) br_if (condition2)
+ // =>
+ // br_if select (condition1) (condition2) (i32.const 0)
+ // In other words, we replace an if (3 bytes) with a select and a
+ // zero (also 3 bytes). The size is unchanged, but the select may
+ // be further optimizable, and if select does not branch we also
+ // avoid one branch.
+ // If running the br's condition unconditionally is too expensive,
+ // give up.
+ auto* zero = LiteralUtils::makeZero(i32, *getModule());
+ if (tooCostlyToRunUnconditionally(
+ getPassOptions(), br->condition, zero)) {
+ return;
+ }
+ // Of course we can't do this if the br's condition has side
+ // effects, as we would then execute those unconditionally.
+ if (EffectAnalyzer(getPassOptions(), br->condition)
+ .hasSideEffects()) {
+ return;
+ }
+ Builder builder(*getModule());
+ // Note that we use the br's condition as the select condition.
+ // That keeps the order of the two conditions as it was originally.
+ br->condition =
+ builder.makeSelect(br->condition, curr->condition, zero);
+ }
br->finalize();
replaceCurrent(Builder(*getModule()).dropIfConcretelyTyped(br));
anotherCycle = true;
@@ -871,14 +917,9 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> {
// This is always helpful for code size, but can be a tradeoff with
// performance as we run both code paths. So when shrinking we always
// try to do this, but otherwise must consider more carefully.
- if (!passOptions.shrinkLevel) {
- // Consider the cost of executing all the code unconditionally
- const auto MAX_COST = 7;
- auto total =
- CostAnalyzer(iff->ifTrue).cost + CostAnalyzer(iff->ifFalse).cost;
- if (total >= MAX_COST) {
- return nullptr;
- }
+ if (tooCostlyToRunUnconditionally(
+ passOptions, iff->ifTrue, iff->ifFalse)) {
+ return nullptr;
}
// Check if side effects allow this.
EffectAnalyzer condition(passOptions, iff->condition);
diff --git a/test/emcc_hello_world.fromasm b/test/emcc_hello_world.fromasm
index a9b17068e..25cbe7176 100644
--- a/test/emcc_hello_world.fromasm
+++ b/test/emcc_hello_world.fromasm
@@ -10327,13 +10327,18 @@
)
)
(block
- (if
- (local.tee $3
- (i32.load
- (i32.const 616)
+ (br_if $label$break$L279
+ (select
+ (i32.eqz
+ (i32.eqz
+ (local.tee $3
+ (i32.load
+ (i32.const 616)
+ )
+ )
+ )
)
- )
- (br_if $label$break$L279
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $12)
diff --git a/test/emcc_hello_world.fromasm.clamp b/test/emcc_hello_world.fromasm.clamp
index 212e5e8d3..8feba2827 100644
--- a/test/emcc_hello_world.fromasm.clamp
+++ b/test/emcc_hello_world.fromasm.clamp
@@ -10377,13 +10377,18 @@
)
)
(block
- (if
- (local.tee $3
- (i32.load
- (i32.const 616)
+ (br_if $label$break$L279
+ (select
+ (i32.eqz
+ (i32.eqz
+ (local.tee $3
+ (i32.load
+ (i32.const 616)
+ )
+ )
+ )
)
- )
- (br_if $label$break$L279
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $12)
diff --git a/test/emcc_hello_world.fromasm.imprecise b/test/emcc_hello_world.fromasm.imprecise
index f6fe8aca1..8bb8c257b 100644
--- a/test/emcc_hello_world.fromasm.imprecise
+++ b/test/emcc_hello_world.fromasm.imprecise
@@ -10223,13 +10223,18 @@
)
)
(block
- (if
- (local.tee $3
- (i32.load
- (i32.const 616)
+ (br_if $label$break$L279
+ (select
+ (i32.eqz
+ (i32.eqz
+ (local.tee $3
+ (i32.load
+ (i32.const 616)
+ )
+ )
+ )
)
- )
- (br_if $label$break$L279
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $12)
diff --git a/test/memorygrowth.fromasm b/test/memorygrowth.fromasm
index 13231d482..f1858e724 100644
--- a/test/memorygrowth.fromasm
+++ b/test/memorygrowth.fromasm
@@ -3152,13 +3152,14 @@
)
)
(block
- (if
- (local.tee $12
- (i32.load
- (i32.const 1648)
+ (br_if $do-once33
+ (select
+ (local.tee $12
+ (i32.load
+ (i32.const 1648)
+ )
)
- )
- (br_if $do-once33
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $8)
diff --git a/test/memorygrowth.fromasm.clamp b/test/memorygrowth.fromasm.clamp
index 13231d482..f1858e724 100644
--- a/test/memorygrowth.fromasm.clamp
+++ b/test/memorygrowth.fromasm.clamp
@@ -3152,13 +3152,14 @@
)
)
(block
- (if
- (local.tee $12
- (i32.load
- (i32.const 1648)
+ (br_if $do-once33
+ (select
+ (local.tee $12
+ (i32.load
+ (i32.const 1648)
+ )
)
- )
- (br_if $do-once33
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $8)
diff --git a/test/memorygrowth.fromasm.imprecise b/test/memorygrowth.fromasm.imprecise
index d6011b1c7..61c455725 100644
--- a/test/memorygrowth.fromasm.imprecise
+++ b/test/memorygrowth.fromasm.imprecise
@@ -3150,13 +3150,14 @@
)
)
(block
- (if
- (local.tee $12
- (i32.load
- (i32.const 1648)
+ (br_if $do-once33
+ (select
+ (local.tee $12
+ (i32.load
+ (i32.const 1648)
+ )
)
- )
- (br_if $do-once33
+ (i32.const 0)
(i32.or
(i32.le_u
(local.get $8)
diff --git a/test/passes/bysyncify_optimize-level=1.txt b/test/passes/bysyncify_optimize-level=1.txt
index 7b1093964..b2bc87f85 100644
--- a/test/passes/bysyncify_optimize-level=1.txt
+++ b/test/passes/bysyncify_optimize-level=1.txt
@@ -1244,11 +1244,12 @@
)
)
)
- (if
- (i32.eqz
- (global.get $__bysyncify_state)
- )
- (br_if $l
+ (br_if $l
+ (select
+ (i32.eqz
+ (global.get $__bysyncify_state)
+ )
+ (i32.const 0)
(local.get $0)
)
)
diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index 944828d5c..790d943c3 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -2431,4 +2431,55 @@
)
)
)
+ (func $if_br_if (; 115 ;) (type $1)
+ (local $0 i32)
+ (block $label$1
+ (br_if $label$1
+ (select
+ (local.tee $0
+ (i32.const 1024)
+ )
+ (i32.const 0)
+ (i32.eqz
+ (i32.const -4)
+ )
+ )
+ )
+ (br_if $label$1
+ (select
+ (i32.const 1025)
+ (i32.const 0)
+ (i32.eqz
+ (i32.const -5)
+ )
+ )
+ )
+ (br_if $label$1
+ (select
+ (local.tee $0
+ (i32.const 1025)
+ )
+ (i32.const 0)
+ (i32.eqz
+ (i32.const -6)
+ )
+ )
+ )
+ (if
+ (i32.const 1026)
+ (br_if $label$1
+ (local.tee $0
+ (i32.const -7)
+ )
+ )
+ )
+ (i32.store
+ (i32.const 1024)
+ (i32.add
+ (local.get $0)
+ (i32.const 1)
+ )
+ )
+ )
+ )
)
diff --git a/test/passes/remove-unused-brs.wast b/test/passes/remove-unused-brs.wast
index 15a56b2d9..c20e352f0 100644
--- a/test/passes/remove-unused-brs.wast
+++ b/test/passes/remove-unused-brs.wast
@@ -2039,5 +2039,53 @@
)
)
)
+ (func $if_br_if
+ (local $0 i32)
+ (block $label$1
+ (if
+ (local.tee $0 ;; note side effect; it's ok
+ (i32.const 1024)
+ )
+ (br_if $label$1
+ (i32.eqz
+ (i32.const -4)
+ )
+ )
+ )
+ (if
+ (i32.const 1025)
+ (br_if $label$1
+ (i32.eqz
+ (i32.const -5)
+ )
+ )
+ )
+ (if
+ (local.tee $0 ;; note side effect; it's ok
+ (i32.const 1025)
+ )
+ (br_if $label$1
+ (i32.eqz
+ (i32.const -6)
+ )
+ )
+ )
+ (if
+ (i32.const 1026)
+ (br_if $label$1
+ (local.tee $0 ;; but here it is *not* ok
+ (i32.const -7)
+ )
+ )
+ )
+ (i32.store
+ (i32.const 1024)
+ (i32.add
+ (local.get $0)
+ (i32.const 1)
+ )
+ )
+ )
+ )
)
diff --git a/test/unit.fromasm b/test/unit.fromasm
index b6065c905..748be4b8e 100644
--- a/test/unit.fromasm
+++ b/test/unit.fromasm
@@ -705,19 +705,17 @@
)
)
(func $loophi (; 45 ;) (; has Stack IR ;) (param $0 i32) (param $1 i32)
- (local $2 i32)
(loop $while-in
(block $while-out
(call $loophi
(local.get $0)
(i32.const 0)
)
- (if
- (local.tee $2
+ (br_if $while-out
+ (select
+ (local.get $0)
+ (i32.const 0)
(local.get $0)
- )
- (br_if $while-out
- (local.get $2)
)
)
(br_if $while-in
@@ -747,9 +745,10 @@
(local.set $2
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $2)
)
)
@@ -779,9 +778,10 @@
(local.set $1
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $1)
)
)
diff --git a/test/unit.fromasm.clamp b/test/unit.fromasm.clamp
index 1a905fee5..0b57f2077 100644
--- a/test/unit.fromasm.clamp
+++ b/test/unit.fromasm.clamp
@@ -753,19 +753,17 @@
)
)
(func $loophi (; 46 ;) (; has Stack IR ;) (param $0 i32) (param $1 i32)
- (local $2 i32)
(loop $while-in
(block $while-out
(call $loophi
(local.get $0)
(i32.const 0)
)
- (if
- (local.tee $2
+ (br_if $while-out
+ (select
+ (local.get $0)
+ (i32.const 0)
(local.get $0)
- )
- (br_if $while-out
- (local.get $2)
)
)
(br_if $while-in
@@ -795,9 +793,10 @@
(local.set $2
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $2)
)
)
@@ -827,9 +826,10 @@
(local.set $1
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $1)
)
)
diff --git a/test/unit.fromasm.imprecise b/test/unit.fromasm.imprecise
index bc2546b6e..f9fc294c5 100644
--- a/test/unit.fromasm.imprecise
+++ b/test/unit.fromasm.imprecise
@@ -693,19 +693,17 @@
)
)
(func $loophi (; 44 ;) (; has Stack IR ;) (param $0 i32) (param $1 i32)
- (local $2 i32)
(loop $while-in
(block $while-out
(call $loophi
(local.get $0)
(i32.const 0)
)
- (if
- (local.tee $2
+ (br_if $while-out
+ (select
+ (local.get $0)
+ (i32.const 0)
(local.get $0)
- )
- (br_if $while-out
- (local.get $2)
)
)
(br_if $while-in
@@ -735,9 +733,10 @@
(local.set $2
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $2)
)
)
@@ -767,9 +766,10 @@
(local.set $1
(local.get $0)
)
- (if
- (call $return_int)
- (br_if $label$break$L7
+ (br_if $label$break$L7
+ (select
+ (call $return_int)
+ (i32.const 0)
(local.get $1)
)
)
generated by cgit v1.2.3 (git 2.39.1) at 2025-08-06 03:42:07 +0000