[NFC] Clean up sign/zero extension code in properties.h (#3404)

Use matchers and more descriptive variable names to clarify the intent of the
functions for finding and inspecting sign extension patterns.

1 files changed, 38 insertions, 48 deletions

diff --git a/src/ir/properties.h b/src/ir/properties.h
index 7ec1701d6..1331eeb73 100644
--- a/src/ir/properties.h
+++ b/src/ir/properties.h
@@ -19,6 +19,7 @@
 
 #include "ir/bits.h"
 #include "ir/effects.h"
+#include "ir/match.h"
 #include "wasm.h"
 
 namespace wasm {
@@ -131,84 +132,73 @@ inline Literals getLiterals(const Expression* curr) {
 // Check if an expression is a sign-extend, and if so, returns the value
 // that is extended, otherwise nullptr
 inline 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;
-                }
-              }
-            }
-          }
-        }
-      }
-    }
+  using namespace Match;
+  int32_t leftShift = 0, rightShift = 0;
+  Expression* extended = nullptr;
+  if (matches(curr,
+              binary(ShrSInt32,
+                     binary(ShlInt32, any(&extended), i32(&leftShift)),
+                     i32(&rightShift))) &&
+      leftShift == rightShift && leftShift != 0) {
+    return extended;
   }
   return nullptr;
 }
 
 // gets the size of the sign-extended value
 inline Index getSignExtBits(Expression* curr) {
-  return 32 - Bits::getEffectiveShifts(curr->cast<Binary>()->right);
+  assert(curr->type == Type::i32);
+  auto* rightShift = curr->cast<Binary>()->right;
+  return 32 - Bits::getEffectiveShifts(rightShift);
 }
 
 // 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)
 inline 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;
-                }
-              }
-            }
-          }
-        }
-      }
-    }
+  using namespace Match;
+  int32_t leftShift = 0, rightShift = 0;
+  Expression* extended = nullptr;
+  if (matches(curr,
+              binary(ShrSInt32,
+                     binary(ShlInt32, any(&extended), i32(&leftShift)),
+                     i32(&rightShift))) &&
+      Bits::getEffectiveShifts(rightShift, Type::i32) <=
+        Bits::getEffectiveShifts(leftShift, Type::i32) &&
+      rightShift != 0) {
+    return extended;
   }
   return nullptr;
 }
 
 // gets the size of the almost sign-extended value, as well as the
 // extra shifts, if any
-inline Index getAlmostSignExtBits(Expression* curr, Index& extraShifts) {
-  extraShifts = Bits::getEffectiveShifts(
-                  curr->cast<Binary>()->left->cast<Binary>()->right) -
-                Bits::getEffectiveShifts(curr->cast<Binary>()->right);
+inline Index getAlmostSignExtBits(Expression* curr, Index& extraLeftShifts) {
+  auto* leftShift = curr->cast<Binary>()->left->cast<Binary>()->right;
+  auto* rightShift = curr->cast<Binary>()->right;
+  extraLeftShifts =
+    Bits::getEffectiveShifts(leftShift) - Bits::getEffectiveShifts(rightShift);
   return getSignExtBits(curr);
 }
 
 // Check if an expression is a zero-extend, and if so, returns the value
 // that is extended, otherwise nullptr
 inline 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;
-        }
-      }
-    }
+  using namespace Match;
+  int32_t mask = 0;
+  Expression* extended = nullptr;
+  if (matches(curr, binary(AndInt32, any(&extended), i32(&mask))) &&
+      Bits::getMaskedBits(mask) != 0) {
+    return extended;
   }
   return nullptr;
 }
 
 // gets the size of the sign-extended value
 inline Index getZeroExtBits(Expression* curr) {
-  return Bits::getMaskedBits(
-    curr->cast<Binary>()->right->cast<Const>()->value.geti32());
+  assert(curr->type == Type::i32);
+  int32_t mask = curr->cast<Binary>()->right->cast<Const>()->value.geti32();
+  return Bits::getMaskedBits(mask);
 }
 
 // Returns a falling-through value, that is, it looks through a local.tee