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-rw-r--r--src/wasm-stack.h554
1 files changed, 57 insertions, 497 deletions
diff --git a/src/wasm-stack.h b/src/wasm-stack.h
index d80618225..ed9245d4f 100644
--- a/src/wasm-stack.h
+++ b/src/wasm-stack.h
@@ -18,6 +18,7 @@
#define wasm_stack_h
#include "ir/branch-utils.h"
+#include "ir/properties.h"
#include "pass.h"
#include "wasm-binary.h"
#include "wasm-traversal.h"
@@ -182,7 +183,7 @@ private:
// Takes binaryen IR and converts it to something else (binary or stack IR)
template<typename SubType>
-class BinaryenIRWriter : public OverriddenVisitor<BinaryenIRWriter<SubType>> {
+class BinaryenIRWriter : public Visitor<BinaryenIRWriter<SubType>> {
public:
BinaryenIRWriter(Function* func) : func(func) {}
@@ -194,50 +195,7 @@ public:
void visitBlock(Block* curr);
void visitIf(If* curr);
void visitLoop(Loop* curr);
- void visitBreak(Break* curr);
- void visitSwitch(Switch* curr);
- void visitCall(Call* curr);
- void visitCallIndirect(CallIndirect* curr);
- void visitLocalGet(LocalGet* curr);
- void visitLocalSet(LocalSet* curr);
- void visitGlobalGet(GlobalGet* curr);
- void visitGlobalSet(GlobalSet* curr);
- void visitLoad(Load* curr);
- void visitStore(Store* curr);
- void visitAtomicRMW(AtomicRMW* curr);
- void visitAtomicCmpxchg(AtomicCmpxchg* curr);
- void visitAtomicWait(AtomicWait* curr);
- void visitAtomicNotify(AtomicNotify* curr);
- void visitAtomicFence(AtomicFence* curr);
- void visitSIMDExtract(SIMDExtract* curr);
- void visitSIMDReplace(SIMDReplace* curr);
- void visitSIMDShuffle(SIMDShuffle* curr);
- void visitSIMDTernary(SIMDTernary* curr);
- void visitSIMDShift(SIMDShift* curr);
- void visitSIMDLoad(SIMDLoad* curr);
- void visitMemoryInit(MemoryInit* curr);
- void visitDataDrop(DataDrop* curr);
- void visitMemoryCopy(MemoryCopy* curr);
- void visitMemoryFill(MemoryFill* curr);
- void visitConst(Const* curr);
- void visitUnary(Unary* curr);
- void visitBinary(Binary* curr);
- void visitSelect(Select* curr);
- void visitReturn(Return* curr);
- void visitHost(Host* curr);
- void visitRefNull(RefNull* curr);
- void visitRefIsNull(RefIsNull* curr);
- void visitRefFunc(RefFunc* curr);
void visitTry(Try* curr);
- void visitThrow(Throw* curr);
- void visitRethrow(Rethrow* curr);
- void visitBrOnExn(BrOnExn* curr);
- void visitNop(Nop* curr);
- void visitUnreachable(Unreachable* curr);
- void visitDrop(Drop* curr);
- void visitPop(Pop* curr);
- void visitTupleMake(TupleMake* curr);
- void visitTupleExtract(TupleExtract* curr);
protected:
Function* func = nullptr;
@@ -275,19 +233,44 @@ void BinaryenIRWriter<SubType>::visitPossibleBlockContents(Expression* curr) {
}
for (auto* child : block->list) {
visit(child);
- }
- if (block->type == Type::unreachable &&
- block->list.back()->type != Type::unreachable) {
- // similar to in visitBlock, here we could skip emitting the block itself,
- // but must still end the 'block' (the contents, really) with an unreachable
- emitUnreachable();
+ // Since this child was unreachable, either this child or one of its
+ // descendants was a source of unreachability that was actually
+ // emitted. Subsequent children won't be reachable, so skip them.
+ if (child->type == Type::unreachable) {
+ break;
+ }
}
}
template<typename SubType>
void BinaryenIRWriter<SubType>::visit(Expression* curr) {
emitDebugLocation(curr);
- OverriddenVisitor<BinaryenIRWriter>::visit(curr);
+ // We emit unreachable instructions that create unreachability, but not
+ // unreachable instructions that just inherit unreachability from their
+ // children, since the latter won't be reached. This (together with logic in
+ // the control flow visitors) also ensures that the final instruction in each
+ // unreachable block is a source of unreachability, which means we don't need
+ // to emit an extra `unreachable` before the end of the block to prevent type
+ // errors.
+ bool hasUnreachableChild = false;
+ for (auto* child : ValueChildIterator(curr)) {
+ visit(child);
+ if (child->type == Type::unreachable) {
+ hasUnreachableChild = true;
+ break;
+ }
+ }
+ if (hasUnreachableChild) {
+ // `curr` is not reachable, so don't emit it.
+ return;
+ }
+ // Control flow requires special handling, but most instructions can be
+ // emitted directly after their children.
+ if (Properties::isControlFlowStructure(curr)) {
+ Visitor<BinaryenIRWriter>::visit(curr);
+ } else {
+ emit(curr);
+ }
}
template<typename SubType>
@@ -295,22 +278,26 @@ void BinaryenIRWriter<SubType>::visitBlock(Block* curr) {
auto visitChildren = [this](Block* curr, Index from) {
auto& list = curr->list;
while (from < list.size()) {
- visit(list[from++]);
+ auto* child = list[from];
+ visit(child);
+ if (child->type == Type::unreachable) {
+ break;
+ }
+ ++from;
}
};
auto afterChildren = [this](Block* curr) {
- if (curr->type == Type::unreachable) {
- // an unreachable block is one that cannot be exited. We cannot encode
- // this directly in wasm, where blocks must be none,i32,i64,f32,f64. Since
- // the block cannot be exited, we can emit an unreachable at the end, and
- // that will always be valid, and then the block is ok as a none
- emitUnreachable();
- }
emitScopeEnd(curr);
if (curr->type == Type::unreachable) {
- // and emit an unreachable *outside* the block too, so later things can
- // pop anything
+ // Since this block is unreachable, no instructions will be emitted after
+ // it in its enclosing scope. That means that this block will be the last
+ // instruction before the end of its parent scope, so its type must match
+ // the type of its parent. But we don't have a concrete type for this
+ // block and we don't know what type its parent expects, so we can't
+ // ensure the types match. To work around this, we insert an `unreachable`
+ // instruction after every unreachable control flow structure and depend
+ // on its polymorphic behavior to paper over any type mismatches.
emitUnreachable();
}
};
@@ -331,12 +318,16 @@ void BinaryenIRWriter<SubType>::visitBlock(Block* curr) {
emit(curr);
visitChildren(curr, 0);
afterChildren(curr);
+ bool childUnreachable = curr->type == Type::unreachable;
// Finish the later parts of all the parent blocks.
while (!parents.empty()) {
auto* parent = parents.back();
parents.pop_back();
- visitChildren(parent, 1);
+ if (!childUnreachable) {
+ visitChildren(parent, 1);
+ }
afterChildren(parent);
+ childUnreachable = parent->type == Type::unreachable;
}
return;
}
@@ -347,13 +338,6 @@ void BinaryenIRWriter<SubType>::visitBlock(Block* curr) {
}
template<typename SubType> void BinaryenIRWriter<SubType>::visitIf(If* curr) {
- visit(curr->condition);
- if (curr->condition->type == Type::unreachable) {
- // this if-else is unreachable because of the condition, i.e., the condition
- // does not exit. So don't emit the if (but do consume the condition)
- emitUnreachable();
- return;
- }
emit(curr);
visitPossibleBlockContents(curr->ifTrue);
@@ -364,11 +348,10 @@ template<typename SubType> void BinaryenIRWriter<SubType>::visitIf(If* curr) {
emitScopeEnd(curr);
if (curr->type == Type::unreachable) {
- // we already handled the case of the condition being unreachable.
- // otherwise, we may still be unreachable, if we are an if-else with both
- // sides unreachable. wasm does not allow this to be emitted directly, so we
- // must do something more. we could do better, but for now we emit an extra
- // unreachable instruction after the if, so it is not consumed itself,
+ // We already handled the case of the condition being unreachable in
+ // `visit`. Otherwise, we may still be unreachable, if we are an if-else
+ // with both sides unreachable. Just like with blocks, we emit an extra
+ // `unreachable` to work around potential type mismatches.
assert(curr->ifFalse);
emitUnreachable();
}
@@ -378,11 +361,6 @@ template<typename SubType>
void BinaryenIRWriter<SubType>::visitLoop(Loop* curr) {
emit(curr);
visitPossibleBlockContents(curr->body);
- if (curr->type == Type::unreachable) {
- // we emitted a loop without a return type, and the body might be block
- // contents, so ensure it is not consumed
- emitUnreachable();
- }
emitScopeEnd(curr);
if (curr->type == Type::unreachable) {
// we emitted a loop without a return type, so it must not be consumed
@@ -390,361 +368,6 @@ void BinaryenIRWriter<SubType>::visitLoop(Loop* curr) {
}
}
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitBreak(Break* curr) {
- if (curr->value) {
- visit(curr->value);
- }
- if (curr->condition) {
- visit(curr->condition);
- }
- emit(curr);
- if (curr->condition && curr->type == Type::unreachable) {
- // a br_if is normally none or emits a value. if it is unreachable, then
- // either the condition or the value is unreachable, which is extremely
- // rare, and may require us to make the stack polymorphic (if the block we
- // branch to has a value, we may lack one as we are not a reachable branch;
- // the wasm spec on the other hand does presume the br_if emits a value of
- // the right type, even if it popped unreachable)
- emitUnreachable();
- }
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSwitch(Switch* curr) {
- if (curr->value) {
- visit(curr->value);
- }
- visit(curr->condition);
- if (!BranchUtils::isBranchReachable(curr)) {
- // if the branch is not reachable, then it's dangerous to emit it, as wasm
- // type checking rules are different, especially in unreachable code. so
- // just don't emit that unreachable code.
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitCall(Call* curr) {
- for (auto* operand : curr->operands) {
- visit(operand);
- }
-
- // For non-control-flow value-returning instructions, if the type of an
- // expression is unreachable, we emit an unreachable and don't emit the
- // instruction itself. If we don't emit an unreachable, instructions that
- // follow can have a validation failure in wasm binary format. For example:
- // [unreachable] (f32.add
- // [unreachable] (i32.eqz
- // [unreachable] (unreachable)
- // )
- // ...
- // )
- // This is a valid prgram in binaryen IR, because the unreachable type
- // propagates out of an expression, making both i32.eqz and f32.add
- // unreachable. But in binary format, this becomes:
- // unreachable
- // i32.eqz
- // f32.add ;; validation failure; it takes an i32!
- // And here f32.add causes validation failure in wasm validation. So in this
- // case we add an unreachable to prevent following instructions to consume
- // the current value (here i32.eqz).
- //
- // The same applies for other expressions.
- if (curr->type == Type::unreachable && !curr->isReturn) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitCallIndirect(CallIndirect* curr) {
- for (auto* operand : curr->operands) {
- visit(operand);
- }
- visit(curr->target);
- if (curr->type == Type::unreachable && !curr->isReturn) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitLocalGet(LocalGet* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitLocalSet(LocalSet* curr) {
- visit(curr->value);
- if (curr->isTee() && curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitGlobalGet(GlobalGet* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitGlobalSet(GlobalSet* curr) {
- visit(curr->value);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitLoad(Load* curr) {
- visit(curr->ptr);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitStore(Store* curr) {
- visit(curr->ptr);
- visit(curr->value);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitAtomicRMW(AtomicRMW* curr) {
- visit(curr->ptr);
- visit(curr->value);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitAtomicCmpxchg(AtomicCmpxchg* curr) {
- visit(curr->ptr);
- visit(curr->expected);
- visit(curr->replacement);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitAtomicWait(AtomicWait* curr) {
- visit(curr->ptr);
- visit(curr->expected);
- visit(curr->timeout);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitAtomicNotify(AtomicNotify* curr) {
- visit(curr->ptr);
- visit(curr->notifyCount);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitAtomicFence(AtomicFence* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDExtract(SIMDExtract* curr) {
- visit(curr->vec);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDReplace(SIMDReplace* curr) {
- visit(curr->vec);
- visit(curr->value);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDShuffle(SIMDShuffle* curr) {
- visit(curr->left);
- visit(curr->right);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDTernary(SIMDTernary* curr) {
- visit(curr->a);
- visit(curr->b);
- visit(curr->c);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDShift(SIMDShift* curr) {
- visit(curr->vec);
- visit(curr->shift);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSIMDLoad(SIMDLoad* curr) {
- visit(curr->ptr);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitMemoryInit(MemoryInit* curr) {
- visit(curr->dest);
- visit(curr->offset);
- visit(curr->size);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitDataDrop(DataDrop* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitMemoryCopy(MemoryCopy* curr) {
- visit(curr->dest);
- visit(curr->source);
- visit(curr->size);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitMemoryFill(MemoryFill* curr) {
- visit(curr->dest);
- visit(curr->value);
- visit(curr->size);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitConst(Const* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitUnary(Unary* curr) {
- visit(curr->value);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitBinary(Binary* curr) {
- visit(curr->left);
- visit(curr->right);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitSelect(Select* curr) {
- visit(curr->ifTrue);
- visit(curr->ifFalse);
- visit(curr->condition);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitReturn(Return* curr) {
- if (curr->value) {
- visit(curr->value);
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitHost(Host* curr) {
- switch (curr->op) {
- case MemorySize: {
- break;
- }
- case MemoryGrow: {
- visit(curr->operands[0]);
- break;
- }
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitRefNull(RefNull* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitRefIsNull(RefIsNull* curr) {
- visit(curr->value);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitRefFunc(RefFunc* curr) {
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
template<typename SubType> void BinaryenIRWriter<SubType>::visitTry(Try* curr) {
emit(curr);
visitPossibleBlockContents(curr->body);
@@ -756,69 +379,6 @@ template<typename SubType> void BinaryenIRWriter<SubType>::visitTry(Try* curr) {
}
}
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitThrow(Throw* curr) {
- for (auto* operand : curr->operands) {
- visit(operand);
- }
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitRethrow(Rethrow* curr) {
- visit(curr->exnref);
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitBrOnExn(BrOnExn* curr) {
- visit(curr->exnref);
- emit(curr);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- }
-}
-
-template<typename SubType> void BinaryenIRWriter<SubType>::visitNop(Nop* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitUnreachable(Unreachable* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitDrop(Drop* curr) {
- visit(curr->value);
- emit(curr);
-}
-
-template<typename SubType> void BinaryenIRWriter<SubType>::visitPop(Pop* curr) {
- emit(curr);
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitTupleMake(TupleMake* curr) {
- for (auto* operand : curr->operands) {
- visit(operand);
- }
- emit(curr);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- }
-}
-
-template<typename SubType>
-void BinaryenIRWriter<SubType>::visitTupleExtract(TupleExtract* curr) {
- visit(curr->tuple);
- if (curr->type == Type::unreachable) {
- emitUnreachable();
- return;
- }
- emit(curr);
-}
-
// Binaryen IR to binary writer
class BinaryenIRToBinaryWriter
: public BinaryenIRWriter<BinaryenIRToBinaryWriter> {
generated by cgit v1.2.3 (git 2.39.1) at 2025-08-05 18:08:47 +0000