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-rw-r--r--src/passes/AlignmentLowering.cpp178
1 files changed, 160 insertions, 18 deletions
diff --git a/src/passes/AlignmentLowering.cpp b/src/passes/AlignmentLowering.cpp
index 818189056..26815b389 100644
--- a/src/passes/AlignmentLowering.cpp
+++ b/src/passes/AlignmentLowering.cpp
@@ -27,16 +27,15 @@
namespace wasm {
struct AlignmentLowering : public WalkerPass<PostWalker<AlignmentLowering>> {
- void visitLoad(Load* curr) {
+ // Core lowering of a 32-bit load: ensures it is done using aligned
+ // operations, which means we can leave it alone if it's already aligned, or
+ // else we break it up into smaller loads that are.
+ Expression* lowerLoadI32(Load* curr) {
if (curr->align == 0 || curr->align == curr->bytes) {
- return;
+ return curr;
}
Builder builder(*getModule());
- if (curr->type == Type::unreachable) {
- replaceCurrent(curr->ptr);
- return;
- }
- assert(curr->type == Type::i32); // TODO: i64, f32, f64
+ assert(curr->type == Type::i32);
auto temp = builder.addVar(getFunction(), Type::i32);
Expression* ret;
if (curr->bytes == 2) {
@@ -125,21 +124,16 @@ struct AlignmentLowering : public WalkerPass<PostWalker<AlignmentLowering>> {
} else {
WASM_UNREACHABLE("invalid size");
}
- replaceCurrent(
- builder.makeBlock({builder.makeLocalSet(temp, curr->ptr), ret}));
+ return builder.makeBlock({builder.makeLocalSet(temp, curr->ptr), ret});
}
- void visitStore(Store* curr) {
+ // Core lowering of a 32-bit store.
+ Expression* lowerStoreI32(Store* curr) {
if (curr->align == 0 || curr->align == curr->bytes) {
- return;
+ return curr;
}
Builder builder(*getModule());
- if (curr->type == Type::unreachable) {
- replaceCurrent(builder.makeBlock(
- {builder.makeDrop(curr->ptr), builder.makeDrop(curr->value)}));
- return;
- }
- assert(curr->value->type == Type::i32); // TODO: i64, f32, f64
+ assert(curr->value->type == Type::i32);
auto tempPtr = builder.addVar(getFunction(), Type::i32);
auto tempValue = builder.addVar(getFunction(), Type::i32);
auto* block =
@@ -222,7 +216,155 @@ struct AlignmentLowering : public WalkerPass<PostWalker<AlignmentLowering>> {
WASM_UNREACHABLE("invalid size");
}
block->finalize();
- replaceCurrent(block);
+ return block;
+ }
+
+ void visitLoad(Load* curr) {
+ // If unreachable, just remove the load, which removes the unaligned
+ // operation in a trivial way.
+ if (curr->type == Type::unreachable) {
+ replaceCurrent(curr->ptr);
+ return;
+ }
+ if (curr->align == 0 || curr->align == curr->bytes) {
+ // Nothing to do: leave the node unchanged. All code lower down assumes
+ // the operation is unaligned.
+ return;
+ }
+ Builder builder(*getModule());
+ auto type = curr->type.getSingle();
+ Expression* replacement;
+ switch (type) {
+ default:
+ WASM_UNREACHABLE("unhandled unaligned load");
+ case Type::i32:
+ replacement = lowerLoadI32(curr);
+ break;
+ case Type::f32:
+ curr->type = Type::i32;
+ replacement = builder.makeUnary(ReinterpretInt32, lowerLoadI32(curr));
+ break;
+ case Type::i64:
+ case Type::f64:
+ if (type == Type::i64 && curr->bytes != 8) {
+ // A load of <64 bits.
+ curr->type = Type::i32;
+ replacement = builder.makeUnary(
+ curr->signed_ ? ExtendSInt32 : ExtendUInt32, lowerLoadI32(curr));
+ break;
+ }
+ // Load two 32-bit pieces, and combine them.
+ auto temp = builder.addVar(getFunction(), Type::i32);
+ auto* set = builder.makeLocalSet(temp, curr->ptr);
+ Expression* low =
+ lowerLoadI32(builder.makeLoad(4,
+ false,
+ curr->offset,
+ curr->align,
+ builder.makeLocalGet(temp, Type::i32),
+ Type::i32));
+ low = builder.makeUnary(ExtendUInt32, low);
+ // Note that the alignment is assumed to be the same here, even though
+ // we add an offset of 4. That is because this is an unaligned load, so
+ // the alignment is 1, 2, or 4, which means it stays the same after
+ // adding 4.
+ Expression* high =
+ lowerLoadI32(builder.makeLoad(4,
+ false,
+ curr->offset + 4,
+ curr->align,
+ builder.makeLocalGet(temp, Type::i32),
+ Type::i32));
+ high = builder.makeUnary(ExtendUInt32, high);
+ high =
+ builder.makeBinary(ShlInt64, high, builder.makeConst(int64_t(32)));
+ auto* combined = builder.makeBinary(OrInt64, low, high);
+ replacement = builder.makeSequence(set, combined);
+ // Ensure the proper output type.
+ if (type == Type::f64) {
+ replacement = builder.makeUnary(ReinterpretInt64, replacement);
+ }
+ break;
+ }
+ replaceCurrent(replacement);
+ }
+
+ void visitStore(Store* curr) {
+ Builder builder(*getModule());
+ // If unreachable, just remove the store, which removes the unaligned
+ // operation in a trivial way.
+ if (curr->type == Type::unreachable) {
+ replaceCurrent(builder.makeBlock(
+ {builder.makeDrop(curr->ptr), builder.makeDrop(curr->value)}));
+ return;
+ }
+ if (curr->align == 0 || curr->align == curr->bytes) {
+ // Nothing to do: leave the node unchanged. All code lower down assumes
+ // the operation is unaligned.
+ return;
+ }
+ auto type = curr->value->type.getSingle();
+ Expression* replacement;
+ switch (type) {
+ default:
+ WASM_UNREACHABLE("unhandled unaligned store");
+ case Type::i32:
+ replacement = lowerStoreI32(curr);
+ break;
+ case Type::f32:
+ curr->type = Type::i32;
+ curr->value = builder.makeUnary(ReinterpretFloat32, curr->value);
+ replacement = lowerStoreI32(curr);
+ break;
+ case Type::i64:
+ case Type::f64:
+ if (type == Type::i64 && curr->bytes != 8) {
+ // A store of <64 bits.
+ curr->type = Type::i32;
+ curr->value = builder.makeUnary(WrapInt64, curr->value);
+ replacement = lowerStoreI32(curr);
+ break;
+ }
+ // Otherwise, fall through to f64 case for a 64-bit load.
+ // Ensure an integer input value.
+ auto* value = curr->value;
+ if (type == Type::f64) {
+ value = builder.makeUnary(ReinterpretFloat64, value);
+ }
+ // Store as two 32-bit pieces.
+ auto tempPtr = builder.addVar(getFunction(), Type::i32);
+ auto* setPtr = builder.makeLocalSet(tempPtr, curr->ptr);
+ auto tempValue = builder.addVar(getFunction(), Type::i64);
+ auto* setValue = builder.makeLocalSet(tempValue, value);
+ Expression* low = builder.makeUnary(
+ WrapInt64, builder.makeLocalGet(tempValue, Type::i64));
+ low = lowerStoreI32(
+ builder.makeStore(4,
+ curr->offset,
+ curr->align,
+ builder.makeLocalGet(tempPtr, Type::i32),
+ low,
+ Type::i32));
+ Expression* high =
+ builder.makeBinary(ShrUInt64,
+ builder.makeLocalGet(tempValue, Type::i64),
+ builder.makeConst(int64_t(32)));
+ high = builder.makeUnary(WrapInt64, high);
+ // Note that the alignment is assumed to be the same here, even though
+ // we add an offset of 4. That is because this is an unaligned store, so
+ // the alignment is 1, 2, or 4, which means it stays the same after
+ // adding 4.
+ high = lowerStoreI32(
+ builder.makeStore(4,
+ curr->offset + 4,
+ curr->align,
+ builder.makeLocalGet(tempPtr, Type::i32),
+ high,
+ Type::i32));
+ replacement = builder.makeBlock({setPtr, setValue, low, high});
+ break;
+ }
+ replaceCurrent(replacement);
}
};
generated by cgit v1.2.3 (git 2.39.1) at 2025-08-05 23:08:17 +0000