Add support for unary plus in hydrogen compiler.

Also strength-reduction of unary minus.
Fixes issue 1248.

BUG=1248

Review URL: http://codereview.chromium.org/6685045

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7217 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -4552,7 +4552,13 @@ void HGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
       VisitForEffect(expr->expression());
     }
 
-  } else if (op == Token::BIT_NOT || op == Token::SUB) {
+  } else if (op == Token::TYPEOF) {
+    VisitForTypeOf(expr->expression());
+    if (HasStackOverflow()) return;
+    HValue* value = Pop();
+    ast_context()->ReturnInstruction(new HTypeof(value), expr->id());
+
+  } else {
     VISIT_FOR_VALUE(expr->expression());
     HValue* value = Pop();
     HInstruction* instr = NULL;
@@ -4561,20 +4567,16 @@ void HGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
         instr = new HBitNot(value);
         break;
       case Token::SUB:
-        instr = new HMul(graph_->GetConstantMinus1(), value);
+        instr = new HMul(value, graph_->GetConstantMinus1());
+        break;
+      case Token::ADD:
+        instr = new HMul(value, graph_->GetConstant1());
         break;
       default:
-        UNREACHABLE();
+        BAILOUT("Value: unsupported unary operation");
         break;
     }
     ast_context()->ReturnInstruction(instr, expr->id());
-  } else if (op == Token::TYPEOF) {
-    VisitForTypeOf(expr->expression());
-    if (HasStackOverflow()) return;
-    HValue* value = Pop();
-    ast_context()->ReturnInstruction(new HTypeof(value), expr->id());
-  } else {
-    BAILOUT("Value: unsupported unary operation");
   }
 }
 

src/ia32/lithium-codegen-ia32.cc

@@ -893,7 +893,49 @@ void LCodeGen::DoMulI(LMulI* instr) {
   }
 
   if (right->IsConstantOperand()) {
-    __ imul(left, left, ToInteger32(LConstantOperand::cast(right)));
+    // Try strength reductions on the multiplication.
+    // All replacement instructions are at most as long as the imul
+    // and have better latency.
+    int constant = ToInteger32(LConstantOperand::cast(right));
+    if (constant == -1) {
+      __ neg(left);
+    } else if (constant == 0) {
+      __ xor_(left, Operand(left));
+    } else if (constant == 2) {
+      __ add(left, Operand(left));
+    } else if (!instr->hydrogen()->CheckFlag(HValue::kCanOverflow)) {
+      // If we know that the multiplication can't overflow, it's safe to
+      // use instructions that don't set the overflow flag for the
+      // multiplication.
+      switch (constant) {
+        case 1:
+          // Do nothing.
+          break;
+        case 3:
+          __ lea(left, Operand(left, left, times_2, 0));
+          break;
+        case 4:
+          __ shl(left, 2);
+          break;
+        case 5:
+          __ lea(left, Operand(left, left, times_4, 0));
+          break;
+        case 8:
+          __ shl(left, 3);
+          break;
+        case 9:
+          __ lea(left, Operand(left, left, times_8, 0));
+          break;
+       case 16:
+         __ shl(left, 4);
+         break;
+        default:
+          __ imul(left, left, constant);
+          break;
+      }
+    } else {
+      __ imul(left, left, constant);
+    }
   } else {
     __ imul(left, ToOperand(right));
   }