ARM: Improve integer multiplication.

src/arm/lithium-codegen-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1555 matching lines @@
     __ mls(remainder, result, right, left);
     __ cmp(remainder, Operand::Zero());
     __ sub(result, result, Operand(1), LeaveCC, ne);
 
     __ bind(&done);
   }
 }
 
 
 void LCodeGen::DoMulI(LMulI* instr) {
-  Register scratch = scratch0();
   Register result = ToRegister(instr->result());
   // Note that result may alias left.
   Register left = ToRegister(instr->left());
   LOperand* right_op = instr->right();
 
-  bool can_overflow = instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
   bool bailout_on_minus_zero =
     instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero);
+  bool overflow = instr->hydrogen()->CheckFlag(HValue::kCanOverflow);
 
-  if (right_op->IsConstantOperand() && !can_overflow) {
+  if (right_op->IsConstantOperand()) {
     int32_t constant = ToInteger32(LConstantOperand::cast(right_op));
 
     if (bailout_on_minus_zero && (constant < 0)) {
       // The case of a null constant will be handled separately.
       // If constant is negative and left is null, the result should be -0.
       __ cmp(left, Operand::Zero());
       DeoptimizeIf(eq, instr->environment());
     }
 
     switch (constant) {
       case -1:
-        __ rsb(result, left, Operand::Zero());
+        if (overflow) {
+          __ rsb(result, left, Operand::Zero(), SetCC);
+          DeoptimizeIf(vs, instr->environment());
+        } else {
+          __ rsb(result, left, Operand::Zero());
+        }
         break;
       case 0:
         if (bailout_on_minus_zero) {
           // If left is strictly negative and the constant is null, the
           // result is -0. Deoptimize if required, otherwise return 0.
           __ cmp(left, Operand::Zero());
           DeoptimizeIf(mi, instr->environment());
         }
         __ mov(result, Operand::Zero());
         break;
       case 1:
         __ Move(result, left);
         break;
       default:
         // Multiplying by powers of two and powers of two plus or minus
         // one can be done faster with shifted operands.
         // For other constants we emit standard code.
         int32_t mask = constant >> 31;
         uint32_t constant_abs = (constant + mask) ^ mask;
 
-        if (IsPowerOf2(constant_abs) ||
-            IsPowerOf2(constant_abs - 1) ||
-            IsPowerOf2(constant_abs + 1)) {
-          if (IsPowerOf2(constant_abs)) {
-            int32_t shift = WhichPowerOf2(constant_abs);
-            __ mov(result, Operand(left, LSL, shift));
-          } else if (IsPowerOf2(constant_abs - 1)) {
-            int32_t shift = WhichPowerOf2(constant_abs - 1);
-            __ add(result, left, Operand(left, LSL, shift));
-          } else if (IsPowerOf2(constant_abs + 1)) {
-            int32_t shift = WhichPowerOf2(constant_abs + 1);
-            __ rsb(result, left, Operand(left, LSL, shift));
-          }
-
+        if (IsPowerOf2(constant_abs)) {
+          int32_t shift = WhichPowerOf2(constant_abs);
+          __ mov(result, Operand(left, LSL, shift));
           // Correct the sign of the result is the constant is negative.
           if (constant < 0)  __ rsb(result, result, Operand::Zero());
-
+        } else if (IsPowerOf2(constant_abs - 1)) {
+          int32_t shift = WhichPowerOf2(constant_abs - 1);
+          __ add(result, left, Operand(left, LSL, shift));
+          // Correct the sign of the result is the constant is negative.
+          if (constant < 0)  __ rsb(result, result, Operand::Zero());
+        } else if (IsPowerOf2(constant_abs + 1)) {
+          int32_t shift = WhichPowerOf2(constant_abs + 1);
+          __ rsb(result, left, Operand(left, LSL, shift));
+          // Correct the sign of the result is the constant is negative.
+          if (constant < 0)  __ rsb(result, result, Operand::Zero());
         } else {
           // Generate standard code.
           __ mov(ip, Operand(constant));
           __ mul(result, left, ip);
         }
     }
 
   } else {
-    Register right = EmitLoadRegister(right_op, scratch);
-    if (bailout_on_minus_zero) {
-      __ orr(ToRegister(instr->temp()), left, right);
-    }
+    ASSERT(right_op->IsRegister());
+    Register right = ToRegister(right_op);
 
-    if (can_overflow) {
+    if (overflow) {
+      Register scratch = scratch0();
       // scratch:result = left * right.
       if (instr->hydrogen()->representation().IsSmi()) {
         __ SmiUntag(result, left);
         __ smull(result, scratch, result, right);
       } else {
         __ smull(result, scratch, left, right);
       }
       __ cmp(scratch, Operand(result, ASR, 31));
       DeoptimizeIf(ne, instr->environment());
     } else {
       if (instr->hydrogen()->representation().IsSmi()) {
         __ SmiUntag(result, left);
         __ mul(result, result, right);
       } else {
         __ mul(result, left, right);
       }
     }
 
     if (bailout_on_minus_zero) {
-      // Bail out if the result is supposed to be negative zero.
       Label done;
+      __ teq(left, Operand(right));
+      __ b(pl, &done);
+      // Bail out if the result is minus zero.
       __ cmp(result, Operand::Zero());
-      __ b(ne, &done);
-      __ cmp(ToRegister(instr->temp()), Operand::Zero());
-      DeoptimizeIf(mi, instr->environment());
+      DeoptimizeIf(eq, instr->environment());
       __ bind(&done);
     }
   }
 }
 
 
 void LCodeGen::DoBitI(LBitI* instr) {
   LOperand* left_op = instr->left();
   LOperand* right_op = instr->right();
   ASSERT(left_op->IsRegister());
@@ skipping 4094 matching lines @@
   __ sub(scratch, result, Operand::PointerOffsetFromSmiKey(index));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal