notation change: AST => IR (#1245)

The IR is indeed a tree, but not an "abstract syntax tree" since there is no language for which it is the syntax (except in the most trivial and meaningless sense).

1 files changed, 141 insertions, 0 deletions

diff --git a/src/ir/properties.h b/src/ir/properties.h
new file mode 100644
index 000000000..cf481218c
--- /dev/null
+++ b/src/ir/properties.h
@@ -0,0 +1,141 @@
+/*
+ * Copyright 2016 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.
+ */
+
+#ifndef wasm_ir_properties_h
+#define wasm_ir_properties_h
+
+#include "wasm.h"
+#include "ir/bits.h"
+
+namespace wasm {
+
+struct Properties {
+  static bool emitsBoolean(Expression* curr) {
+    if (auto* unary = curr->dynCast<Unary>()) {
+      return unary->isRelational();
+    } else if (auto* binary = curr->dynCast<Binary>()) {
+      return binary->isRelational();
+    }
+    return false;
+  }
+
+  static bool isSymmetric(Binary* binary) {
+    switch (binary->op) {
+      case AddInt32:
+      case MulInt32: 
+      case AndInt32:
+      case OrInt32:
+      case XorInt32:
+      case EqInt32:
+      case NeInt32:
+
+      case AddInt64:
+      case MulInt64: 
+      case AndInt64:
+      case OrInt64:
+      case XorInt64:
+      case EqInt64:
+      case NeInt64: return true;
+
+      default: return false;
+    }
+  }
+
+  // Check if an expression is a sign-extend, and if so, returns the value
+  // that is extended, otherwise nullptr
+  static Expression* getSignExtValue(Expression* curr) {
+    if (auto* outer = curr->dynCast<Binary>()) {
+      if (outer->op == ShrSInt32) {
+        if (auto* outerConst = outer->right->dynCast<Const>()) {
+          if (outerConst->value.geti32() != 0) {
+            if (auto* inner = outer->left->dynCast<Binary>()) {
+              if (inner->op == ShlInt32) {
+                if (auto* innerConst = inner->right->dynCast<Const>()) {
+                  if (outerConst->value == innerConst->value) {
+                    return inner->left;
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    return nullptr;
+  }
+
+  // gets the size of the sign-extended value
+  static Index getSignExtBits(Expression* curr) {
+    return 32 - Bits::getEffectiveShifts(curr->cast<Binary>()->right);
+  }
+
+  // Check if an expression is almost a sign-extend: perhaps the inner shift
+  // is too large. We can split the shifts in that case, which is sometimes
+  // useful (e.g. if we can remove the signext)
+  static Expression* getAlmostSignExt(Expression* curr) {
+    if (auto* outer = curr->dynCast<Binary>()) {
+      if (outer->op == ShrSInt32) {
+        if (auto* outerConst = outer->right->dynCast<Const>()) {
+          if (outerConst->value.geti32() != 0) {
+            if (auto* inner = outer->left->dynCast<Binary>()) {
+              if (inner->op == ShlInt32) {
+                if (auto* innerConst = inner->right->dynCast<Const>()) {
+                  if (Bits::getEffectiveShifts(outerConst) <= Bits::getEffectiveShifts(innerConst)) {
+                    return inner->left;
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    return nullptr;
+  }
+
+  // gets the size of the almost sign-extended value, as well as the
+  // extra shifts, if any
+  static Index getAlmostSignExtBits(Expression* curr, Index& extraShifts) {
+    extraShifts = Bits::getEffectiveShifts(curr->cast<Binary>()->left->cast<Binary>()->right) -
+                  Bits::getEffectiveShifts(curr->cast<Binary>()->right);
+    return getSignExtBits(curr);
+  }
+
+  // Check if an expression is a zero-extend, and if so, returns the value
+  // that is extended, otherwise nullptr
+  static Expression* getZeroExtValue(Expression* curr) {
+    if (auto* binary = curr->dynCast<Binary>()) {
+      if (binary->op == AndInt32) {
+        if (auto* c = binary->right->dynCast<Const>()) {
+          if (Bits::getMaskedBits(c->value.geti32())) {
+            return binary->right;
+          }
+        }
+      }
+    }
+    return nullptr;
+  }
+
+  // gets the size of the sign-extended value
+  static Index getZeroExtBits(Expression* curr) {
+    return Bits::getMaskedBits(curr->cast<Binary>()->right->cast<Const>()->value.geti32());
+  }
+};
+
+} // wasm
+
+#endif // wams_ir_properties_h
+