Improved modulo operation in lithium as well as bailout on -0.

TEST=none
BUG=none

Patch by Rodolph Perfetta from ARM Ltd.

Review URL: http://codereview.chromium.org/6612017


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7300 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1345,29 +1345,25 @@ LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
 
 LInstruction* LChunkBuilder::DoMod(HMod* instr) {
   if (instr->representation().IsInteger32()) {
-    // TODO(1042) The fixed register allocation
-    // is needed because we call GenericBinaryOpStub from
-    // the generated code, which requires registers r0
-    // and r1 to be used. We should remove that
-    // when we provide a native implementation.
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
 
-    LInstruction* result;
+    LModI* mod;
     if (instr->HasPowerOf2Divisor()) {
       ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
       LOperand* value = UseRegisterAtStart(instr->left());
-      LModI* mod = new LModI(value, UseOrConstant(instr->right()));
-      result = DefineSameAsFirst(mod);
-      result = AssignEnvironment(result);
+      mod = new LModI(value, UseOrConstant(instr->right()));
     } else {
-      LOperand* value = UseFixed(instr->left(), r0);
-      LOperand* divisor = UseFixed(instr->right(), r1);
-      result = DefineFixed(new LModI(value, divisor), r0);
-      result = AssignEnvironment(AssignPointerMap(result));
+      LOperand* dividend = UseRegister(instr->left());
+      LOperand* divisor = UseRegisterAtStart(instr->right());
+      mod = new LModI(dividend,
+                      divisor,
+                      TempRegister(),
+                      FixedTemp(d1),
+                      FixedTemp(d2));
     }
 
-    return result;
+    return AssignEnvironment(DefineSameAsFirst(mod));
   } else if (instr->representation().IsTagged()) {
     return DoArithmeticT(Token::MOD, instr);
   } else {

src/arm/lithium-arm.h

@@ -523,11 +523,29 @@ class LArgumentsElements: public LTemplateInstruction<1, 0, 0> {
 };
 
 
-class LModI: public LTemplateInstruction<1, 2, 0> {
+class LModI: public LTemplateInstruction<1, 2, 3> {
  public:
-  LModI(LOperand* left, LOperand* right) {
+  // Used when the right hand is a constant power of 2.
+  LModI(LOperand* left,
+        LOperand* right) {
     inputs_[0] = left;
     inputs_[1] = right;
+    temps_[0] = NULL;
+    temps_[1] = NULL;
+    temps_[2] = NULL;
+  }
+
+  // Used for the standard case.
+  LModI(LOperand* left,
+        LOperand* right,
+        LOperand* temp1,
+        LOperand* temp2,
+        LOperand* temp3) {
+    inputs_[0] = left;
+    inputs_[1] = right;
+    temps_[0] = temp1;
+    temps_[1] = temp2;
+    temps_[2] = temp3;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(ModI, "mod-i")

src/arm/lithium-codegen-arm.cc

@@ -802,7 +802,7 @@ void LCodeGen::DoModI(LModI* instr) {
     if (divisor < 0) divisor = -divisor;
 
     Label positive_dividend, done;
-    __ tst(dividend, Operand(dividend));
+    __ cmp(dividend, Operand(0));
     __ b(pl, &positive_dividend);
     __ rsb(dividend, dividend, Operand(0));
     __ and_(dividend, dividend, Operand(divisor - 1));
@@ -817,55 +817,67 @@ void LCodeGen::DoModI(LModI* instr) {
     return;
   }
 
-  class DeferredModI: public LDeferredCode {
-   public:
-    DeferredModI(LCodeGen* codegen, LModI* instr)
-        : LDeferredCode(codegen), instr_(instr) { }
-    virtual void Generate() {
-      codegen()->DoDeferredBinaryOpStub(instr_, Token::MOD);
-    }
-   private:
-    LModI* instr_;
-  };
   // These registers hold untagged 32 bit values.
   Register left = ToRegister(instr->InputAt(0));
   Register right = ToRegister(instr->InputAt(1));
   Register result = ToRegister(instr->result());
+
   Register scratch = scratch0();
+  Register scratch2 = ToRegister(instr->TempAt(0));
+  DwVfpRegister dividend = ToDoubleRegister(instr->TempAt(1));
+  DwVfpRegister divisor = ToDoubleRegister(instr->TempAt(2));
+  DwVfpRegister quotient = double_scratch0();
+
+  ASSERT(result.is(left));
+
+  ASSERT(!dividend.is(divisor));
+  ASSERT(!dividend.is(quotient));
+  ASSERT(!divisor.is(quotient));
+  ASSERT(!scratch.is(left));
+  ASSERT(!scratch.is(right));
+  ASSERT(!scratch.is(result));
+
+  Label done, vfp_modulo, both_positive, right_negative;
 
-  Label deoptimize, done;
   // Check for x % 0.
   if (instr->hydrogen()->CheckFlag(HValue::kCanBeDivByZero)) {
-    __ tst(right, Operand(right));
-    __ b(eq, &deoptimize);
+    __ cmp(right, Operand(0));
+    DeoptimizeIf(eq, instr->environment());
   }
 
-  // Check for (0 % -x) that will produce negative zero.
-  if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-    Label ok;
-    __ tst(left, Operand(left));
-    __ b(ne, &ok);
-    __ tst(right, Operand(right));
-    __ b(pl, &ok);
-    __ b(al, &deoptimize);
-    __ bind(&ok);
-  }
+  // (0 % x) must yield 0 (if x is finite, which is the case here).
+  __ cmp(left, Operand(0));
+  __ b(eq, &done);
+  // Preload right in a vfp register.
+  __ vmov(divisor.low(), right);
+  __ b(lt, &vfp_modulo);
 
-  // Try a few common cases before using the stub.
-  Label call_stub;
+  __ cmp(left, Operand(right));
+  __ b(lt, &done);
+
+  // Check for (positive) power of two on the right hand side.
+  __ JumpIfNotPowerOfTwoOrZeroAndNeg(right,
+                                     scratch,
+                                     &right_negative,
+                                     &both_positive);
+  // Perform modulo operation (scratch contains right - 1).
+  __ and_(result, scratch, Operand(left));
+  __ b(&done);
+
+  __ bind(&right_negative);
+  // Negate right. The sign of the divisor does not matter.
+  __ rsb(right, right, Operand(0));
+
+  __ bind(&both_positive);
   const int kUnfolds = 3;
-  // Skip if either side is negative.
-  __ cmp(left, Operand(0));
-  __ cmp(right, Operand(0), NegateCondition(mi));
-  __ b(mi, &call_stub);
   // If the right hand side is smaller than the (nonnegative)
-  // left hand side, it is the result. Else try a few subtractions
-  // of the left hand side.
+  // left hand side, the left hand side is the result.
+  // Else try a few subtractions of the left hand side.
   __ mov(scratch, left);
   for (int i = 0; i < kUnfolds; i++) {
     // Check if the left hand side is less or equal than the
     // the right hand side.
-    __ cmp(scratch, right);
+    __ cmp(scratch, Operand(right));
     __ mov(result, scratch, LeaveCC, lt);
     __ b(lt, &done);
     // If not, reduce the left hand side by the right hand
@@ -873,29 +885,45 @@ void LCodeGen::DoModI(LModI* instr) {
     if (i < kUnfolds - 1) __ sub(scratch, scratch, right);
   }
 
-  // Check for power of two on the right hand side.
-  __ JumpIfNotPowerOfTwoOrZero(right, scratch, &call_stub);
-  // Perform modulo operation (scratch contains right - 1).
-  __ and_(result, scratch, Operand(left));
-  __ b(&done);
-
-  __ bind(&call_stub);
-  // Call the stub. The numbers in r0 and r1 have
-  // to be tagged to Smis. If that is not possible, deoptimize.
-  DeferredModI* deferred = new DeferredModI(this, instr);
-  __ TrySmiTag(left, &deoptimize, scratch);
-  __ TrySmiTag(right, &deoptimize, scratch);
-
-  __ b(al, deferred->entry());
-  __ bind(deferred->exit());
-
-  // If the result in r0 is a Smi, untag it, else deoptimize.
-  __ JumpIfNotSmi(result, &deoptimize);
-  __ SmiUntag(result);
+  __ bind(&vfp_modulo);
+  // Load the arguments in VFP registers.
+  // The divisor value is preloaded before. Be careful that 'right' is only live
+  // on entry.
+  __ vmov(dividend.low(), left);
+  // From here on don't use right as it may have been reallocated (for example
+  // to scratch2).
+  right = no_reg;
+
+  __ vcvt_f64_s32(dividend, dividend.low());
+  __ vcvt_f64_s32(divisor, divisor.low());
+
+  // We do not care about the sign of the divisor.
+  __ vabs(divisor, divisor);
+  // Compute the quotient and round it to a 32bit integer.
+  __ vdiv(quotient, dividend, divisor);
+  __ vcvt_s32_f64(quotient.low(), quotient);
+  __ vcvt_f64_s32(quotient, quotient.low());
+
+  // Compute the remainder in result.
+  DwVfpRegister double_scratch = dividend;
+  __ vmul(double_scratch, divisor, quotient);
+  __ vcvt_s32_f64(double_scratch.low(), double_scratch);
+  __ vmov(scratch, double_scratch.low());
+
+  if (!instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
+    __ sub(result, left, scratch);
+  } else {
+    Label ok;
+    // Check for -0.
+    __ sub(scratch2, left, scratch, SetCC);
+    __ b(ne, &ok);
+    __ cmp(left, Operand(0));
+    DeoptimizeIf(mi, instr->environment());
+    __ bind(&ok);
+    // Load the result and we are done.
+    __ mov(result, scratch2);
+  }
 
-  __ b(al, &done);
-  __ bind(&deoptimize);
-  DeoptimizeIf(al, instr->environment());
   __ bind(&done);
 }
 
@@ -919,16 +947,16 @@ void LCodeGen::DoDivI(LDivI* instr) {
 
   // Check for x / 0.
   if (instr->hydrogen()->CheckFlag(HValue::kCanBeDivByZero)) {
-    __ tst(right, right);
+    __ cmp(right, Operand(0));
     DeoptimizeIf(eq, instr->environment());
   }
 
   // Check for (0 / -x) that will produce negative zero.
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     Label left_not_zero;
-    __ tst(left, Operand(left));
+    __ cmp(left, Operand(0));
     __ b(ne, &left_not_zero);
-    __ tst(right, Operand(right));
+    __ cmp(right, Operand(0));
     DeoptimizeIf(mi, instr->environment());
     __ bind(&left_not_zero);
   }
@@ -1035,7 +1063,7 @@ void LCodeGen::DoMulI(LMulI* instr) {
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     // Bail out if the result is supposed to be negative zero.
     Label done;
-    __ tst(left, Operand(left));
+    __ cmp(left, Operand(0));
     __ b(ne, &done);
     if (instr->InputAt(1)->IsConstantOperand()) {
       if (ToInteger32(LConstantOperand::cast(instr->InputAt(1))) <= 0) {
@@ -1900,8 +1928,7 @@ void LCodeGen::DoInstanceOf(LInstanceOf* instr) {
   InstanceofStub stub(InstanceofStub::kArgsInRegisters);
   CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
 
-  Label true_value, done;
-  __ tst(r0, r0);
+  __ cmp(r0, Operand(0));
   __ mov(r0, Operand(factory()->false_value()), LeaveCC, ne);
   __ mov(r0, Operand(factory()->true_value()), LeaveCC, eq);
 }
@@ -1916,7 +1943,7 @@ void LCodeGen::DoInstanceOfAndBranch(LInstanceOfAndBranch* instr) {
 
   InstanceofStub stub(InstanceofStub::kArgsInRegisters);
   CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-  __ tst(r0, Operand(r0));
+  __ cmp(r0, Operand(0));
   EmitBranch(true_block, false_block, eq);
 }
 
@@ -2406,7 +2433,7 @@ void LCodeGen::DoApplyArguments(LApplyArguments* instr) {
   // stack.
   Label invoke, loop;
   // length is a small non-negative integer, due to the test above.
-  __ tst(length, Operand(length));
+  __ cmp(length, Operand(0));
   __ b(eq, &invoke);
   __ bind(&loop);
   __ ldr(scratch, MemOperand(elements, length, LSL, 2));
@@ -2642,6 +2669,7 @@ void LCodeGen::DoMathFloor(LUnaryMathOperation* instr) {
   // Move the result back to general purpose register r0.
   __ vmov(result, single_scratch);
 
+  if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     // Test for -0.
     Label done;
     __ cmp(result, Operand(0));
@@ -2650,6 +2678,7 @@ void LCodeGen::DoMathFloor(LUnaryMathOperation* instr) {
     __ tst(scratch1, Operand(HeapNumber::kSignMask));
     DeoptimizeIf(ne, instr->environment());
     __ bind(&done);
+  }
 }
 
 
@@ -2666,6 +2695,7 @@ void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
   DeoptimizeIf(ne, instr->environment());
   __ vmov(result, double_scratch0().low());
 
+  if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     // Test for -0.
     Label done;
     __ cmp(result, Operand(0));
@@ -2674,6 +2704,7 @@ void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
     __ tst(scratch1, Operand(HeapNumber::kSignMask));
     DeoptimizeIf(ne, instr->environment());
     __ bind(&done);
+  }
 }
 
 

src/arm/macro-assembler-arm.cc

@@ -2489,6 +2489,18 @@ void MacroAssembler::JumpIfNotPowerOfTwoOrZero(
 }
 
 
+void MacroAssembler::JumpIfNotPowerOfTwoOrZeroAndNeg(
+    Register reg,
+    Register scratch,
+    Label* zero_and_neg,
+    Label* not_power_of_two) {
+  sub(scratch, reg, Operand(1), SetCC);
+  b(mi, zero_and_neg);
+  tst(scratch, reg);
+  b(ne, not_power_of_two);
+}
+
+
 void MacroAssembler::JumpIfNotBothSmi(Register reg1,
                                       Register reg2,
                                       Label* on_not_both_smi) {

src/arm/macro-assembler-arm.h

@@ -826,6 +826,16 @@ class MacroAssembler: public Assembler {
   void JumpIfNotPowerOfTwoOrZero(Register reg,
                                  Register scratch,
                                  Label* not_power_of_two_or_zero);
+  // Check whether the value of reg is a power of two and not zero.
+  // Control falls through if it is, with scratch containing the mask
+  // value (reg - 1).
+  // Otherwise control jumps to the 'zero_and_neg' label if the value of reg is
+  // zero or negative, or jumps to the 'not_power_of_two' label if the value is
+  // strictly positive but not a power of two.
+  void JumpIfNotPowerOfTwoOrZeroAndNeg(Register reg,
+                                       Register scratch,
+                                       Label* zero_and_neg,
+                                       Label* not_power_of_two);
 
   // ---------------------------------------------------------------------------
   // Smi utilities