[csa] Re-introduce automatic constant folding for IntPtrAdd and IntPtrSub

src/compiler/code-assembler.cc

Index: src/compiler/code-assembler.cc
diff --git a/src/compiler/code-assembler.cc b/src/compiler/code-assembler.cc
index 4844355abb08e61a694f9ae669e201477a21cf67..e136f80558ee995445194e7cdf0869d0a4325a56 100644
--- a/src/compiler/code-assembler.cc
+++ b/src/compiler/code-assembler.cc
@@ -209,6 +209,10 @@ bool CodeAssembler::ToSmiConstant(Node* node, Smi*& out_value) {
 }
 
 bool CodeAssembler::ToIntPtrConstant(Node* node, intptr_t& out_value) {
+  if (node->opcode() == IrOpcode::kBitcastWordToTaggedSigned ||
+      node->opcode() == IrOpcode::kBitcastWordToTagged) {
+    node = node->InputAt(0);
+  }
   IntPtrMatcher m(node);
   if (m.HasValue()) out_value = m.Value();
   return m.HasValue();
@@ -269,6 +273,51 @@ Node* CodeAssembler::LoadStackPointer() {
 CODE_ASSEMBLER_BINARY_OP_LIST(DEFINE_CODE_ASSEMBLER_BINARY_OP)
 #undef DEFINE_CODE_ASSEMBLER_BINARY_OP
 
+Node* CodeAssembler::IntPtrAdd(Node* left, Node* right) {
+  intptr_t left_constant;
+  bool is_left_constant = ToIntPtrConstant(left, left_constant);
+  intptr_t right_constant;
+  bool is_right_constant = ToIntPtrConstant(right, right_constant);
+  if (is_left_constant) {
+    if (is_right_constant) {
+      intptr_t sum = left_constant + right_constant;
+      if (sum >= std::numeric_limits<int32_t>::min() &&

[Igor Sheludko, 2016/12/28 15:57:05]

I think we can always return the sum.

[danno, 2016/12/28 16:05:33]

Done.

+          sum <= std::numeric_limits<int32_t>::max()) {
+        return IntPtrConstant(sum);
+      }
+    }
+    if (left_constant == 0) {
+      return right;
+    }
+  } else if (is_right_constant) {
+    if (right_constant == 0) {
+      return left;
+    }
+  }
+  return raw_assembler()->IntPtrAdd(left, right);
+}
+
+Node* CodeAssembler::IntPtrSub(Node* left, Node* right) {
+  intptr_t left_constant;
+  bool is_left_constant = ToIntPtrConstant(left, left_constant);
+  intptr_t right_constant;
+  bool is_right_constant = ToIntPtrConstant(right, right_constant);
+  if (is_left_constant) {
+    if (is_right_constant) {
+      intptr_t diff = left_constant - right_constant;
+      if (diff >= std::numeric_limits<int32_t>::min() &&

[Igor Sheludko, 2016/12/28 15:57:05]

Same here.

[danno, 2016/12/28 16:05:33]

Done.

+          diff <= std::numeric_limits<int32_t>::max()) {
+        return IntPtrConstant(diff);
+      }
+    }
+  } else if (is_right_constant) {
+    if (right_constant == 0) {
+      return left;
+    }
+  }
+  return raw_assembler()->IntPtrSub(left, right);
+}
+
 Node* CodeAssembler::WordShl(Node* value, int shift) {
   return (shift != 0) ? raw_assembler()->WordShl(value, IntPtrConstant(shift))
                       : value;