Tweaks on Math.pow (ia32 and x64).

Review URL: http://codereview.chromium.org/8831008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10203 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/assembler.cc

@@ -1115,19 +1115,7 @@ double power_double_int(double x, int y) {
 double power_double_double(double x, double y) {
   // The checks for special cases can be dropped in ia32 because it has already
   // been done in generated code before bailing out here.
-#if !defined(V8_TARGET_ARCH_IA32)
-  int y_int = static_cast<int>(y);
-  if (y == y_int) {
-    return power_double_int(x, y_int);  // Returns 1.0 for exponent 0.
-  }
-  if (!isinf(x)) {
-    if (y == 0.5) return sqrt(x + 0.0);  // -0 must be converted to +0.
-    if (y == -0.5) return 1.0 / sqrt(x + 0.0);
-  }
-#endif
-  if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) {
-    return OS::nan_value();
-  }
+  if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) return OS::nan_value();
   return pow(x, y);
 }
 

src/ia32/code-stubs-ia32.cc

@@ -2948,8 +2948,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   const XMMRegister double_exponent = xmm1;
   const XMMRegister double_scratch = xmm4;
 
-  Label double_int_runtime, generic_runtime, done;
-  Label exponent_not_smi, int_exponent;
+  Label call_runtime, done, exponent_not_smi, int_exponent;
 
   // Save 1 in double_result - we need this several times later on.
   __ mov(scratch, Immediate(1));
@@ -2966,7 +2965,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ JumpIfSmi(base, &base_is_smi, Label::kNear);
     __ cmp(FieldOperand(base, HeapObject::kMapOffset),
            factory->heap_number_map());
-    __ j(not_equal, &generic_runtime);
+    __ j(not_equal, &call_runtime);
 
     __ movdbl(double_base, FieldOperand(base, HeapNumber::kValueOffset));
     __ jmp(&unpack_exponent, Label::kNear);
@@ -2983,7 +2982,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ bind(&exponent_not_smi);
     __ cmp(FieldOperand(exponent, HeapObject::kMapOffset),
            factory->heap_number_map());
-    __ j(not_equal, &generic_runtime);
+    __ j(not_equal, &call_runtime);
     __ movdbl(double_exponent,
               FieldOperand(exponent, HeapNumber::kValueOffset));
   } else if (exponent_type_ == TAGGED) {
@@ -3002,7 +3001,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ cvttsd2si(exponent, Operand(double_exponent));
     // Skip to runtime if possibly NaN (indicated by the indefinite integer).
     __ cmp(exponent, Immediate(0x80000000u));
-    __ j(equal, &generic_runtime);
+    __ j(equal, &call_runtime);
     __ cvtsi2sd(double_scratch, exponent);
     // Already ruled out NaNs for exponent.
     __ ucomisd(double_exponent, double_scratch);
@@ -3119,33 +3118,35 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ bind(&fast_power_failed);
     __ fninit();
     __ add(esp, Immediate(kDoubleSize));
-    __ jmp(&generic_runtime);
+    __ jmp(&call_runtime);
   }
 
   // Calculate power with integer exponent.
   __ bind(&int_exponent);
   const XMMRegister double_scratch2 = double_exponent;
-  __ mov(scratch, exponent);      // Back up exponent.
+  __ mov(scratch, exponent);  // Back up exponent.
   __ movsd(double_scratch, double_base);  // Back up base.
   __ movsd(double_scratch2, double_result);  // Load double_exponent with 1.
 
   // Get absolute value of exponent.
-  Label while_true, no_multiply;
-  const uint32_t kClearSignBitMask = 0x7FFFFFFF;
-  __ and_(exponent, Immediate(kClearSignBitMask));
+  Label no_neg, while_true, no_multiply;
+  __ test(scratch, scratch);
+  __ j(positive, &no_neg, Label::kNear);
+  __ neg(scratch);
+  __ bind(&no_neg);
 
   __ bind(&while_true);
-  __ shr(exponent, 1);
+  __ shr(scratch, 1);
   __ j(not_carry, &no_multiply, Label::kNear);
-  __ mulsd(double_result, double_base);
+  __ mulsd(double_result, double_scratch);
   __ bind(&no_multiply);
 
-  __ mulsd(double_base, double_base);
+  __ mulsd(double_scratch, double_scratch);
   __ j(not_zero, &while_true);
 
   // scratch has the original value of the exponent - if the exponent is
   // negative, return 1/result.
-  __ test(scratch, scratch);
+  __ test(exponent, exponent);
   __ j(positive, &done);
   __ divsd(double_scratch2, double_result);
   __ movsd(double_result, double_scratch2);
@@ -3153,47 +3154,36 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   // Due to subnormals, x^-y == (1/x)^y does not hold in all cases.
   __ xorps(double_scratch2, double_scratch2);
   __ ucomisd(double_scratch2, double_result);  // Result cannot be NaN.
-  __ j(equal, &double_int_runtime);
+  // double_exponent aliased as double_scratch2 has already been overwritten
+  // and may not have contained the exponent value in the first place when the
+  // exponent is a smi.  We reset it with exponent value before bailing out.
+  __ j(not_equal, &done);
+  __ cvtsi2sd(double_exponent, exponent);
 
   // Returning or bailing out.
+  Counters* counters = masm->isolate()->counters();
   if (exponent_type_ == ON_STACK) {
+    // The arguments are still on the stack.
+    __ bind(&call_runtime);
+    __ TailCallRuntime(Runtime::kMath_pow_cfunction, 2, 1);
+
     // The stub is called from non-optimized code, which expects the result
     // as heap number in exponent.
     __ bind(&done);
-    __ AllocateHeapNumber(exponent, scratch, base, &generic_runtime);
-    __ movdbl(FieldOperand(exponent, HeapNumber::kValueOffset), double_result);
+    __ AllocateHeapNumber(eax, scratch, base, &call_runtime);
+    __ movdbl(FieldOperand(eax, HeapNumber::kValueOffset), double_result);
+    __ IncrementCounter(counters->math_pow(), 1);
     __ ret(2 * kPointerSize);
-
-    // The arguments are still on the stack.
-    __ bind(&generic_runtime);
-    __ bind(&double_int_runtime);
-    __ TailCallRuntime(Runtime::kMath_pow_cfunction, 2, 1);
   } else {
-    __ jmp(&done);
-
-    Label return_from_runtime;
-    __ bind(&generic_runtime);
+    __ bind(&call_runtime);
     {
       AllowExternalCallThatCantCauseGC scope(masm);
-      __ PrepareCallCFunction(4, exponent);
+      __ PrepareCallCFunction(4, scratch);
       __ movdbl(Operand(esp, 0 * kDoubleSize), double_base);
       __ movdbl(Operand(esp, 1 * kDoubleSize), double_exponent);
       __ CallCFunction(
           ExternalReference::power_double_double_function(masm->isolate()), 4);
     }
-    __ jmp(&return_from_runtime, Label::kNear);
-
-    __ bind(&double_int_runtime);
-    {
-      AllowExternalCallThatCantCauseGC scope(masm);
-      __ PrepareCallCFunction(4, exponent);
-      __ movdbl(Operand(esp, 0 * kDoubleSize), double_scratch);
-      __ mov(Operand(esp, 1 * kDoubleSize), scratch);
-      __ CallCFunction(
-          ExternalReference::power_double_int_function(masm->isolate()), 4);
-    }
-
-    __ bind(&return_from_runtime);
     // Return value is in st(0) on ia32.
     // Store it into the (fixed) result register.
     __ sub(esp, Immediate(kDoubleSize));
@@ -3202,6 +3192,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ add(esp, Immediate(kDoubleSize));
 
     __ bind(&done);
+    __ IncrementCounter(counters->math_pow(), 1);
     __ ret(0);
   }
 }

src/runtime.cc

@@ -7398,7 +7398,8 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_log) {
   return isolate->transcendental_cache()->Get(TranscendentalCache::LOG, x);
 }
 
-
+// Slow version of Math.pow.  We check for fast paths for special cases.
+// Used if SSE2/VFP3 is not available.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_pow) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
@@ -7414,25 +7415,36 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_pow) {
   }
 
   CONVERT_DOUBLE_ARG_CHECKED(y, 1);
-  // Returning a smi would not confuse crankshaft as this part of code is only
-  // run if SSE2 was not available, in which case crankshaft is disabled.
-  if (y == 0) return Smi::FromInt(1);  // Returns 1 if exponent is 0.
-  return isolate->heap()->AllocateHeapNumber(power_double_double(x, y));
+  int y_int = static_cast<int>(y);
+  double result;
+  if (y == y_int) {
+    result = power_double_int(x, y_int);  // Returns 1 if exponent is 0.
+  } else  if (y == 0.5) {
+    result = (isinf(x)) ? V8_INFINITY : sqrt(x + 0.0);  // Convert -0 to +0.
+  } else if (y == -0.5) {
+    result = (isinf(x)) ? 0 : 1.0 / sqrt(x + 0.0);  // Convert -0 to +0.
+  } else {
+    result = power_double_double(x, y);
+  }
+  if (isnan(result)) return isolate->heap()->nan_value();
+  return isolate->heap()->AllocateHeapNumber(result);
 }
 
-// Fast version of Math.pow if we know that y is not an integer and
-// y is not -0.5 or 0.5. Used as slowcase from codegen.
+// Fast version of Math.pow if we know that y is not an integer and y is not
+// -0.5 or 0.5.  Used as slow case from fullcodegen.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_pow_cfunction) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
+  isolate->counters()->math_pow()->Increment();
+
   CONVERT_DOUBLE_ARG_CHECKED(x, 0);
   CONVERT_DOUBLE_ARG_CHECKED(y, 1);
   if (y == 0) {
     return Smi::FromInt(1);
-  } else if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) {
-    return isolate->heap()->nan_value();
   } else {
-    return isolate->heap()->AllocateHeapNumber(pow(x, y));
+    double result = power_double_double(x, y);
+    if (isnan(result)) return isolate->heap()->nan_value();
+    return isolate->heap()->AllocateHeapNumber(result);
   }
 }
 

src/x64/code-stubs-x64.cc

@@ -2004,8 +2004,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   const XMMRegister double_exponent = xmm1;
   const XMMRegister double_scratch = xmm4;
 
-  Label double_int_runtime, generic_runtime, done;
-  Label exponent_not_smi, int_exponent;
+  Label call_runtime, done, exponent_not_smi, int_exponent;
 
   // Save 1 in double_result - we need this several times later on.
   __ movq(scratch, Immediate(1));
@@ -2021,7 +2020,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ JumpIfSmi(base, &base_is_smi, Label::kNear);
     __ CompareRoot(FieldOperand(base, HeapObject::kMapOffset),
                    Heap::kHeapNumberMapRootIndex);
-    __ j(not_equal, &generic_runtime);
+    __ j(not_equal, &call_runtime);
 
     __ movsd(double_base, FieldOperand(base, HeapNumber::kValueOffset));
     __ jmp(&unpack_exponent, Label::kNear);
@@ -2038,7 +2037,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ bind(&exponent_not_smi);
     __ CompareRoot(FieldOperand(exponent, HeapObject::kMapOffset),
                    Heap::kHeapNumberMapRootIndex);
-    __ j(not_equal, &generic_runtime);
+    __ j(not_equal, &call_runtime);
     __ movsd(double_exponent, FieldOperand(exponent, HeapNumber::kValueOffset));
   } else if (exponent_type_ == TAGGED) {
     __ JumpIfNotSmi(exponent, &exponent_not_smi, Label::kNear);
@@ -2055,7 +2054,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ cvttsd2si(exponent, double_exponent);
     // Skip to runtime if possibly NaN (indicated by the indefinite integer).
     __ cmpl(exponent, Immediate(0x80000000u));
-    __ j(equal, &generic_runtime);
+    __ j(equal, &call_runtime);
     __ cvtlsi2sd(double_scratch, exponent);
     // Already ruled out NaNs for exponent.
     __ ucomisd(double_exponent, double_scratch);
@@ -2169,7 +2168,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ bind(&fast_power_failed);
     __ fninit();
     __ addq(rsp, Immediate(kDoubleSize));
-    __ jmp(&generic_runtime);
+    __ jmp(&call_runtime);
   }
 
   // Calculate power with integer exponent.
@@ -2181,9 +2180,11 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ movsd(double_scratch2, double_result);  // Load double_exponent with 1.
 
   // Get absolute value of exponent.
-  Label while_true, no_multiply;
-  const uint32_t kClearSignBitMask = 0x7FFFFFFF;
-  __ andl(scratch, Immediate(kClearSignBitMask));
+  Label no_neg, while_true, no_multiply;
+  __ testl(scratch, scratch);
+  __ j(positive, &no_neg, Label::kNear);
+  __ negl(scratch);
+  __ bind(&no_neg);
 
   __ bind(&while_true);
   __ shrl(scratch, Immediate(1));
@@ -2194,8 +2195,7 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   __ mulsd(double_scratch, double_scratch);
   __ j(not_zero, &while_true);
 
-  // scratch has the original value of the exponent - if the exponent is
-  // negative, return 1/result.
+  // If the exponent is negative, return 1/result.
   __ testl(exponent, exponent);
   __ j(greater, &done);
   __ divsd(double_scratch2, double_result);
@@ -2204,27 +2204,28 @@ void MathPowStub::Generate(MacroAssembler* masm) {
   // Due to subnormals, x^-y == (1/x)^y does not hold in all cases.
   __ xorps(double_scratch2, double_scratch2);
   __ ucomisd(double_scratch2, double_result);
-  __ j(equal, &double_int_runtime);
+  // double_exponent aliased as double_scratch2 has already been overwritten
+  // and may not have contained the exponent value in the first place when the
+  // input was a smi.  We reset it with exponent value before bailing out.
+  __ j(not_equal, &done);
+  __ cvtlsi2sd(double_exponent, exponent);
 
   // Returning or bailing out.
+  Counters* counters = masm->isolate()->counters();
   if (exponent_type_ == ON_STACK) {
+    // The arguments are still on the stack.
+    __ bind(&call_runtime);
+    __ TailCallRuntime(Runtime::kMath_pow_cfunction, 2, 1);
+
     // The stub is called from non-optimized code, which expects the result
     // as heap number in eax.
     __ bind(&done);
-    __ AllocateHeapNumber(rax, rcx, &generic_runtime);
+    __ AllocateHeapNumber(rax, rcx, &call_runtime);
     __ movsd(FieldOperand(rax, HeapNumber::kValueOffset), double_result);
+    __ IncrementCounter(counters->math_pow(), 1);
     __ ret(2 * kPointerSize);
-
-    // The arguments are still on the stack.
-    __ bind(&generic_runtime);
-    __ bind(&double_int_runtime);
-    __ TailCallRuntime(Runtime::kMath_pow_cfunction, 2, 1);
   } else {
-    __ jmp(&done);
-
-    Label return_from_runtime;
-    StubRuntimeCallHelper callhelper;
-    __ bind(&generic_runtime);
+    __ bind(&call_runtime);
     // Move base to the correct argument register.  Exponent is already in xmm1.
     __ movsd(xmm0, double_base);
     ASSERT(double_exponent.is(xmm1));
@@ -2234,27 +2235,13 @@ void MathPowStub::Generate(MacroAssembler* masm) {
       __ CallCFunction(
           ExternalReference::power_double_double_function(masm->isolate()), 2);
     }
-    __ jmp(&return_from_runtime, Label::kNear);
-
-    __ bind(&double_int_runtime);
-    // Move base to the correct argument register.
-    __ movsd(xmm0, double_base);
-    // Exponent is already in the correct argument register:
-    // edi (not rdi) on Linux and edx on Windows.
-    {
-      AllowExternalCallThatCantCauseGC scope(masm);
-      __ PrepareCallCFunction(2);
-      __ CallCFunction(
-          ExternalReference::power_double_int_function(masm->isolate()), 2);
-    }
-
-    __ bind(&return_from_runtime);
     // Return value is in xmm0.
     __ movsd(double_result, xmm0);
     // Restore context register.
     __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
 
     __ bind(&done);
+    __ IncrementCounter(counters->math_pow(), 1);
     __ ret(0);
   }
 }