summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--src/passes/MergeBlocks.cpp103
-rw-r--r--test/passes/remove-unused-names_merge-blocks.txt86
-rw-r--r--test/passes/remove-unused-names_merge-blocks.wast40
3 files changed, 171 insertions, 58 deletions
diff --git a/src/passes/MergeBlocks.cpp b/src/passes/MergeBlocks.cpp
index 7591aa50a..4fa2c651e 100644
--- a/src/passes/MergeBlocks.cpp
+++ b/src/passes/MergeBlocks.cpp
@@ -154,6 +154,15 @@ struct BreakValueDropper : public ControlFlowWalker<BreakValueDropper> {
}
};
+static bool hasUnreachableChild(Block* block) {
+ for (auto* test : block->list) {
+ if (test->type == unreachable) {
+ return true;
+ }
+ }
+ return false;
+}
+
// core block optimizer routine
static void optimizeBlock(Block* curr, Module* module, PassOptions& passOptions) {
bool more = true;
@@ -168,42 +177,37 @@ static void optimizeBlock(Block* curr, Module* module, PassOptions& passOptions)
if (drop) {
child = drop->value->dynCast<Block>();
if (child) {
- // if we move around unreachable code, type changes could occur. avoid that, as
- // anyhow it means we should have run dce before getting here
- for (auto* test : child->list) {
- if (test->type == unreachable) {
+ if (hasUnreachableChild(child)) {
+ // don't move around unreachable code, as it can change types
+ // dce should have been run anyhow
+ continue;
+ }
+ if (child->name.is()) {
+ Expression* expression = child;
+ // check if it's ok to remove the value from all breaks to us
+ ProblemFinder finder(passOptions);
+ finder.origin = child->name;
+ finder.walk(expression);
+ if (finder.found()) {
child = nullptr;
- break;
+ } else {
+ // fix up breaks
+ BreakValueDropper fixer(passOptions);
+ fixer.origin = child->name;
+ fixer.setModule(module);
+ fixer.walk(expression);
}
}
if (child) {
- if (child->name.is()) {
- Expression* expression = child;
- // check if it's ok to remove the value from all breaks to us
- ProblemFinder finder(passOptions);
- finder.origin = child->name;
- finder.walk(expression);
- if (finder.found()) {
- child = nullptr;
- } else {
- // fix up breaks
- BreakValueDropper fixer(passOptions);
- fixer.origin = child->name;
- fixer.setModule(module);
- fixer.walk(expression);
- }
- }
- if (child) {
- // we can do it!
- // reuse the drop
- drop->value = child->list.back();
- drop->finalize();
- child->list.back() = drop;
- child->finalize();
- curr->list[i] = child;
- more = true;
- changed = true;
- }
+ // we can do it!
+ // reuse the drop
+ drop->value = child->list.back();
+ drop->finalize();
+ child->list.back() = drop;
+ child->finalize();
+ curr->list[i] = child;
+ more = true;
+ changed = true;
}
}
}
@@ -251,6 +255,23 @@ struct MergeBlocks : public WalkerPass<PostWalker<MergeBlocks>> {
optimizeBlock(curr, getModule(), getPassOptions());
}
+ // given
+ // (curr
+ // (block=child
+ // (..more..)
+ // (back)
+ // )
+ // (..other..children..)
+ // )
+ // if child is a block, we can move this around to
+ // (block
+ // (..more..)
+ // (curr
+ // (back)
+ // (..other..children..)
+ // )
+ // )
+ // at which point the block is on the outside and potentially mergeable with an outer block
Block* optimize(Expression* curr, Expression*& child, Block* outer = nullptr, Expression** dependency1 = nullptr, Expression** dependency2 = nullptr) {
if (!child) return outer;
if ((dependency1 && *dependency1) || (dependency2 && *dependency2)) {
@@ -261,18 +282,28 @@ struct MergeBlocks : public WalkerPass<PostWalker<MergeBlocks>> {
}
if (auto* block = child->dynCast<Block>()) {
if (!block->name.is() && block->list.size() >= 2) {
- child = block->list.back();
+ // if we move around unreachable code, type changes could occur. avoid that, as
+ // anyhow it means we should have run dce before getting here
+ if (curr->type == none && hasUnreachableChild(block)) {
+ // moving the block to the outside would replace a none with an unreachable
+ return outer;
+ }
+ auto* back = block->list.back();
+ if (back->type == unreachable) {
+ // curr is not reachable, dce could remove it; don't try anything fancy
+ // here
+ return outer;
+ }
+ child = back;
// we modified child (which is a reference to a pointer), which modifies curr, which might change its type
// (e.g. (drop (block (result i32) .. (unreachable)))
// the child was a block of i32, and is being replaced with an unreachable, so the
// parent will likely need to be unreachable too
- auto oldType = curr->type;
- ReFinalize().walk(curr);
if (outer == nullptr) {
// reuse the block, move it out
block->list.back() = curr;
// we want the block outside to have the same type as curr had
- block->finalize(oldType);
+ block->finalize(curr->type);
replaceCurrent(block);
return block;
} else {
diff --git a/test/passes/remove-unused-names_merge-blocks.txt b/test/passes/remove-unused-names_merge-blocks.txt
index 53424063d..7769b1ac8 100644
--- a/test/passes/remove-unused-names_merge-blocks.txt
+++ b/test/passes/remove-unused-names_merge-blocks.txt
@@ -166,11 +166,13 @@
(i32.const 20)
)
)
- (drop
- (i32.const 10)
- )
(return
- (unreachable)
+ (block
+ (drop
+ (i32.const 10)
+ )
+ (unreachable)
+ )
)
)
(func $binary (type $3)
@@ -297,14 +299,16 @@
)
)
)
- (unreachable)
- (drop
- (i32.const 20)
- )
(drop
- (i32.add
- (i32.const 10)
- (i32.const 30)
+ (block (result i32)
+ (unreachable)
+ (drop
+ (i32.const 20)
+ )
+ (i32.add
+ (i32.const 10)
+ (i32.const 30)
+ )
)
)
)
@@ -460,7 +464,7 @@
(drop
(select
(i32.const 20)
- (block
+ (block (result i32)
(unreachable)
(i32.const 40)
)
@@ -478,7 +482,7 @@
(drop
(select
(i32.const 20)
- (block
+ (block (result i32)
(drop
(i32.const 30)
)
@@ -502,7 +506,7 @@
(select
(i32.const 20)
(i32.const 40)
- (block
+ (block (result i32)
(unreachable)
(i32.const 60)
)
@@ -518,7 +522,7 @@
(select
(i32.const 20)
(i32.const 40)
- (block
+ (block (result i32)
(drop
(i32.const 50)
)
@@ -639,7 +643,7 @@
)
(call $call-ii
(i32.const 20)
- (block
+ (block (result i32)
(unreachable)
(i32.const 30)
)
@@ -649,7 +653,7 @@
)
(call $call-ii
(i32.const 20)
- (block
+ (block (result i32)
(drop
(i32.const 30)
)
@@ -826,12 +830,14 @@
)
(func $return-different-type (type $4) (result i32)
(drop
- (i32.const 2)
- )
- (drop
(f64.abs
- (return
- (i32.const 1)
+ (block
+ (drop
+ (i32.const 2)
+ )
+ (return
+ (i32.const 1)
+ )
)
)
)
@@ -850,4 +856,40 @@
(unreachable)
(f64.const -1)
)
+ (func $dont-move-unreachable (type $3)
+ (loop $label$0
+ (drop
+ (block (result i32)
+ (br $label$0)
+ (i32.const 1)
+ )
+ )
+ )
+ )
+ (func $dont-move-unreachable-last (type $3)
+ (loop $label$0
+ (drop
+ (block (result i32)
+ (call $dont-move-unreachable-last)
+ (br $label$0)
+ )
+ )
+ )
+ )
+ (func $move-around-unreachable-in-middle (type $3)
+ (loop $label$0
+ (nop)
+ (drop
+ (block $label$3 (result i32)
+ (drop
+ (br_if $label$3
+ (br $label$0)
+ (i32.const 0)
+ )
+ )
+ (i32.const 1)
+ )
+ )
+ )
+ )
)
diff --git a/test/passes/remove-unused-names_merge-blocks.wast b/test/passes/remove-unused-names_merge-blocks.wast
index c249a34dd..1233ef538 100644
--- a/test/passes/remove-unused-names_merge-blocks.wast
+++ b/test/passes/remove-unused-names_merge-blocks.wast
@@ -1014,4 +1014,44 @@
(f64.const -1)
)
)
+ (func $dont-move-unreachable
+ (loop $label$0
+ (drop
+ (block $label$3 (result i32)
+ (br $label$0)
+ (i32.const 1)
+ )
+ )
+ )
+ )
+ (func $dont-move-unreachable-last
+ (loop $label$0
+ (drop
+ (block $label$3 (result i32)
+ (call $dont-move-unreachable-last)
+ (br $label$0)
+ )
+ )
+ )
+ )
+ (func $move-around-unreachable-in-middle
+ (loop $label$0
+ (drop
+ (block $label$2 (result i32)
+ (block $block2
+ (nop)
+ )
+ (block $label$3 (result i32)
+ (drop
+ (br_if $label$3
+ (br $label$0)
+ (i32.const 0)
+ )
+ )
+ (i32.const 1)
+ )
+ )
+ )
+ )
+ )
)
generated by cgit v1.2.3 (git 2.39.1) at 2025-08-06 18:04:31 +0000