1 files changed, 106 insertions, 0 deletions
diff --git a/src/passes/RemoveCopysign.cpp b/src/passes/RemoveCopysign.cpp
new file mode 100644
index 000000000..2b57441ee
--- /dev/null
+++ b/src/passes/RemoveCopysign.cpp
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2018 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Removes the `f32.copysign` and `f64.copysign` instructions and replaces them
+// with equivalent bit operations. Primarily intended to be used with `wasm2asm`
+// where `Math.copysign` doesn't exist.
+//
+
+#include <wasm.h>
+#include <pass.h>
+
+#include "wasm-builder.h"
+
+namespace wasm {
+
+struct RemoveCopysignPass : public WalkerPass<PostWalker<RemoveCopysignPass>> {
+  bool isFunctionParallel() override { return false; }
+
+  Pass* create() override { return new RemoveCopysignPass; }
+
+  void doWalkModule(Module* module) {
+    if (!builder) builder = make_unique<Builder>(*module);
+    PostWalker<RemoveCopysignPass>::doWalkModule(module);
+  }
+
+  void doWalkFunction(Function* func) {
+    if (!builder) builder = make_unique<Builder>(*getModule());
+    PostWalker<RemoveCopysignPass>::doWalkFunction(func);
+  }
+
+  void visitBinary(Binary *curr) {
+    Literal signBit, otherBits;
+    UnaryOp int2float, float2int;
+    BinaryOp bitAnd, bitOr;
+    switch (curr->op) {
+      case CopySignFloat32:
+        float2int = ReinterpretFloat32;
+        int2float = ReinterpretInt32;
+        bitAnd = AndInt32;
+        bitOr = OrInt32;
+        signBit = Literal(uint32_t(1 << 31));
+        otherBits = Literal(uint32_t(1 << 31) - 1);
+        break;
+
+      case CopySignFloat64:
+        float2int = ReinterpretFloat64;
+        int2float = ReinterpretInt64;
+        bitAnd = AndInt64;
+        bitOr = OrInt64;
+        signBit = Literal(uint64_t(1) << 63);
+        otherBits = Literal((uint64_t(1) << 63) - 1);
+        break;
+
+      default: return;
+    }
+
+    replaceCurrent(
+      builder->makeUnary(
+        int2float,
+        builder->makeBinary(
+          bitOr,
+          builder->makeBinary(
+            bitAnd,
+            builder->makeUnary(
+              float2int,
+              curr->left
+            ),
+            builder->makeConst(otherBits)
+          ),
+          builder->makeBinary(
+            bitAnd,
+            builder->makeUnary(
+              float2int,
+              curr->right
+            ),
+            builder->makeConst(signBit)
+          )
+        )
+      )
+    );
+  }
+
+private:
+  std::unique_ptr<Builder> builder;
+};
+
+Pass *createRemoveCopysignPass() {
+  return new RemoveCopysignPass();
+}
+
+} // namespace wasm
+