Improve code for integral modulus calculation.

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 548da2e40904f936f6b1940d390a2fd188e70287..5bc6fa0f68df86579583aace5bddebdabb49fcd1 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1446,43 +1446,62 @@ LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
 
 
 LInstruction* LChunkBuilder::DoMod(HMod* instr) {
+  HValue* left = instr->left();
+  HValue* right = instr->right();
   if (instr->representation().IsInteger32()) {
-    ASSERT(instr->left()->representation().IsInteger32());
-    ASSERT(instr->right()->representation().IsInteger32());
-
-    LModI* mod;
+    ASSERT(left->representation().IsInteger32());
+    ASSERT(right->representation().IsInteger32());
     if (instr->HasPowerOf2Divisor()) {
-      ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
-      LOperand* value = UseRegisterAtStart(instr->left());
-      mod = new(zone()) LModI(value, UseOrConstant(instr->right()));
-    } else {
-      LOperand* dividend = UseRegister(instr->left());
-      LOperand* divisor = UseRegister(instr->right());
-      mod = new(zone()) LModI(dividend,
-                              divisor,
-                              TempRegister(),
-                              FixedTemp(d10),
-                              FixedTemp(d11));
-    }
-
-    if (instr->CheckFlag(HValue::kBailoutOnMinusZero) ||
-        instr->CheckFlag(HValue::kCanBeDivByZero) ||
-        instr->CheckFlag(HValue::kCanOverflow)) {
+      ASSERT(!right->CanBeZero());
+      LModI* mod = new(zone()) LModI(UseRegisterAtStart(left),
+                                     UseOrConstant(right));
+      LInstruction* result = DefineAsRegister(mod);
+      return (left->CanBeNegative() &&
+              instr->CheckFlag(HValue::kBailoutOnMinusZero))
+          ? AssignEnvironment(result)
+          : result;
+    } else if (instr->has_fixed_right_arg()) {
+      LModI* mod = new(zone()) LModI(UseRegisterAtStart(left),
+                                     UseRegisterAtStart(right));
       return AssignEnvironment(DefineAsRegister(mod));
+    } else if (CpuFeatures::IsSupported(SUDIV)) {
+      LModI* mod = new(zone()) LModI(UseRegister(left),
+                                     UseRegister(right));
+      LInstruction* result = DefineAsRegister(mod);
+      return (right->CanBeZero() ||
+              (left->RangeCanInclude(kMinInt) &&
+               right->RangeCanInclude(-1) &&
+               instr->CheckFlag(HValue::kBailoutOnMinusZero)) ||
+              (left->CanBeNegative() &&
+               instr->CanBeZero() &&
+               instr->CheckFlag(HValue::kBailoutOnMinusZero)))
+          ? AssignEnvironment(result)
+          : result;
     } else {
-      return DefineAsRegister(mod);
+      LModI* mod = new(zone()) LModI(UseRegister(left),
+                                     UseRegister(right),
+                                     TempRegister(),
+                                     FixedTemp(d10),
+                                     FixedTemp(d11));
+      LInstruction* result = DefineAsRegister(mod);
+      return (right->CanBeZero() ||
+              (left->CanBeNegative() &&
+               instr->CanBeZero() &&
+               instr->CheckFlag(HValue::kBailoutOnMinusZero)))
+          ? AssignEnvironment(result)
+          : result;
     }
   } else if (instr->representation().IsSmiOrTagged()) {
     return DoArithmeticT(Token::MOD, instr);
   } else {
     ASSERT(instr->representation().IsDouble());
-    // We call a C function for double modulo. It can't trigger a GC.
-    // We need to use fixed result register for the call.
+    // We call a C function for double modulo. It can't trigger a GC. We need
+    // to use fixed result register for the call.
     // TODO(fschneider): Allow any register as input registers.
-    LOperand* left = UseFixedDouble(instr->left(), d1);
-    LOperand* right = UseFixedDouble(instr->right(), d2);
-    LArithmeticD* result = new(zone()) LArithmeticD(Token::MOD, left, right);
-    return MarkAsCall(DefineFixedDouble(result, d1), instr);
+    LArithmeticD* mod = new(zone()) LArithmeticD(Token::MOD,
+                                                 UseFixedDouble(left, d1),

[Rodolph Perfetta, 2013/06/07 19:55:03]

Technically not part of your patch but why are we using d1 and d2? The hardfp
abi will use d0 and d1 so this will generate some extra moves.

The same happens on ia32 so I presume there is (was?) a reason. Note that on
ia32 right is in d1 and left in d2 so only left will be moved before the call.
We could do the same for ARM.

[Sven Panne, 2013/06/10 11:05:39]

Good questions, but I don't have immediate answers to them. I'd like to
investigate this in a follow-up CL to get this CL into the tree as quick as
possible.

+                                                 UseFixedDouble(right, d2));
+    return MarkAsCall(DefineFixedDouble(mod, d1), instr);
   }
 }