Porting Math.pow changes to x64.

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 6bea2dc685c8329dcb53eab5cd7cf3b0f7d6d859..35c24e2f8989e0868be09cdd872290e8b5eedb14 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -2940,64 +2940,72 @@ void FloatingPointHelper::CheckFloatOperandsAreInt32(MacroAssembler* masm,
 void MathPowStub::Generate(MacroAssembler* masm) {
   CpuFeatures::Scope use_sse2(SSE2);
   Factory* factory = masm->isolate()->factory();
+  const Register exponent = eax;
+  const Register base = edx;
+  const Register scratch = ecx;
+  const XMMRegister double_result = xmm3;
+  const XMMRegister double_base = xmm2;
+  const XMMRegister double_exponent = xmm1;
+  const XMMRegister double_scratch = xmm4;
+
   Label double_int_runtime, generic_runtime, done;
-  Label base_is_smi, unpack_exponent, exponent_not_smi, int_exponent;
-  // Save 1 in xmm3 - we need this several times later on.
-  __ mov(ecx, Immediate(1));
-  __ cvtsi2sd(xmm3, ecx);
+  Label exponent_not_smi, int_exponent;
+
+  // Save 1 in double_result - we need this several times later on.
+  __ mov(scratch, Immediate(1));
+  __ cvtsi2sd(double_result, scratch);
 
   if (exponent_type_ == ON_STACK) {
-    // The exponent (and base) are supplied as arguments on the stack.
+    Label base_is_smi, unpack_exponent;
+    // The exponent and base are supplied as arguments on the stack.
     // This can only happen if the stub is called from non-optimized code.
-    // Load input parameters from stack
-    __ mov(edx, Operand(esp, 2 * kPointerSize));
-    __ mov(eax, Operand(esp, 1 * kPointerSize));
-    // edx: base (smi or heap number)
-    // eax: exponent (smi or heap number)
-    __ JumpIfSmi(edx, &base_is_smi, Label::kNear);
-    __ cmp(FieldOperand(edx, HeapObject::kMapOffset),
+    // Load input parameters from stack.
+    __ mov(base, Operand(esp, 2 * kPointerSize));
+    __ mov(exponent, Operand(esp, 1 * kPointerSize));
+
+    __ JumpIfSmi(base, &base_is_smi, Label::kNear);
+    __ cmp(FieldOperand(base, HeapObject::kMapOffset),
            factory->heap_number_map());
     __ j(not_equal, &generic_runtime);
 
-    __ movdbl(xmm1, FieldOperand(edx, HeapNumber::kValueOffset));
+    __ movdbl(double_base, FieldOperand(base, HeapNumber::kValueOffset));
     __ jmp(&unpack_exponent, Label::kNear);
 
     __ bind(&base_is_smi);
-    __ SmiUntag(edx);
-    __ cvtsi2sd(xmm1, edx);
+    __ SmiUntag(base);
+    __ cvtsi2sd(double_base, base);
     __ bind(&unpack_exponent);
 
-    __ JumpIfNotSmi(eax, &exponent_not_smi, Label::kNear);
-    __ SmiUntag(eax);
+    __ JumpIfNotSmi(exponent, &exponent_not_smi, Label::kNear);
+    __ SmiUntag(exponent);
     __ jmp(&int_exponent);
 
     __ bind(&exponent_not_smi);
-    __ cmp(FieldOperand(eax, HeapObject::kMapOffset),
+    __ cmp(FieldOperand(exponent, HeapObject::kMapOffset),
            factory->heap_number_map());
     __ j(not_equal, &generic_runtime);
-    __ movdbl(xmm2, FieldOperand(eax, HeapNumber::kValueOffset));
+    __ movdbl(double_exponent,
+              FieldOperand(exponent, HeapNumber::kValueOffset));
   } else if (exponent_type_ == TAGGED) {
-    // xmm1: base as double
-    // eax: exponent (smi or heap number)
-    __ JumpIfNotSmi(eax, &exponent_not_smi, Label::kNear);
-    __ SmiUntag(eax);
+    __ JumpIfNotSmi(exponent, &exponent_not_smi, Label::kNear);
+    __ SmiUntag(exponent);
     __ jmp(&int_exponent);
 
     __ bind(&exponent_not_smi);
-    __ movdbl(xmm2, FieldOperand(eax, HeapNumber::kValueOffset));
+    __ movdbl(double_exponent,
+              FieldOperand(exponent, HeapNumber::kValueOffset));
   }
 
   if (exponent_type_ != INTEGER) {
     Label fast_power;
-    // xmm1: base as double that is not +/- Infinity or NaN
-    // xmm2: exponent as double
     // Detect integer exponents stored as double.
-    __ cvttsd2si(eax, Operand(xmm2));
+    __ cvttsd2si(exponent, Operand(double_exponent));
     // Skip to runtime if possibly NaN (indicated by the indefinite integer).
-    __ cmp(eax, Immediate(0x80000000u));
+    __ cmp(exponent, Immediate(0x80000000u));
     __ j(equal, &generic_runtime);
-    __ cvtsi2sd(xmm4, eax);
-    __ ucomisd(xmm2, xmm4);  // Already ruled out NaNs for exponent.
+    __ cvtsi2sd(double_scratch, exponent);
+    // Already ruled out NaNs for exponent.
+    __ ucomisd(double_exponent, double_scratch);
     __ j(equal, &int_exponent);
 
     if (exponent_type_ == ON_STACK) {
@@ -3006,71 +3014,70 @@ void MathPowStub::Generate(MacroAssembler* masm) {
       // for non-constant cases of +/-0.5 as these hardly occur.
       Label continue_sqrt, continue_rsqrt, not_plus_half;
       // Test for 0.5.
-      // Load xmm4 with 0.5.
-      __ mov(ecx, Immediate(0x3F000000u));
-      __ movd(xmm4, ecx);
-      __ cvtss2sd(xmm4, xmm4);
-      // xmm4 now has 0.5.
-      __ ucomisd(xmm4, xmm2);  // Already ruled out NaNs for exponent.
+      // Load double_scratch with 0.5.
+      __ mov(scratch, Immediate(0x3F000000u));
+      __ movd(double_scratch, scratch);
+      __ cvtss2sd(double_scratch, double_scratch);
+      // Already ruled out NaNs for exponent.
+      __ ucomisd(double_scratch, double_exponent);
       __ j(not_equal, &not_plus_half, Label::kNear);
 
       // Calculates square root of base.  Check for the special case of
       // Math.pow(-Infinity, 0.5) == Infinity (ECMA spec, 15.8.2.13).
       // According to IEEE-754, single-precision -Infinity has the highest
       // 9 bits set and the lowest 23 bits cleared.
-      __ mov(ecx, 0xFF800000u);
-      __ movd(xmm4, ecx);
-      __ cvtss2sd(xmm4, xmm4);
-      __ ucomisd(xmm1, xmm4);
+      __ mov(scratch, 0xFF800000u);
+      __ movd(double_scratch, scratch);
+      __ cvtss2sd(double_scratch, double_scratch);
+      __ ucomisd(double_base, double_scratch);
       // Comparing -Infinity with NaN results in "unordered", which sets the
       // zero flag as if both were equal.  However, it also sets the carry flag.
       __ j(not_equal, &continue_sqrt, Label::kNear);
       __ j(carry, &continue_sqrt, Label::kNear);
 
       // Set result to Infinity in the special case.
-      __ xorps(xmm3, xmm3);
-      __ subsd(xmm3, xmm4);
+      __ xorps(double_result, double_result);
+      __ subsd(double_result, double_scratch);
       __ jmp(&done);
 
       __ bind(&continue_sqrt);
       // sqrtsd returns -0 when input is -0.  ECMA spec requires +0.
-      __ xorps(xmm4, xmm4);
-      __ addsd(xmm4, xmm1);  // Convert -0 to +0.
-      __ sqrtsd(xmm3, xmm4);
+      __ xorps(double_scratch, double_scratch);
+      __ addsd(double_scratch, double_base);  // Convert -0 to +0.
+      __ sqrtsd(double_result, double_scratch);
       __ jmp(&done);
 
       // Test for -0.5.
       __ bind(&not_plus_half);
-      // Load xmm2 with -0.5.
-      // Since xmm3 is 1 and xmm4 is 0.5 this is simply xmm4 - xmm3.
-      __ subsd(xmm4, xmm3);
-      // xmm4 now has -0.5.
-      __ ucomisd(xmm4, xmm2);  // Already ruled out NaNs for exponent.
+      // Load double_exponent with -0.5 by substracting 1.
+      __ subsd(double_scratch, double_result);
+      // Already ruled out NaNs for exponent.
+      __ ucomisd(double_scratch, double_exponent);
       __ j(not_equal, &fast_power, Label::kNear);
 
       // Calculates reciprocal of square root of base.  Check for the special
       // case of Math.pow(-Infinity, -0.5) == 0 (ECMA spec, 15.8.2.13).
       // According to IEEE-754, single-precision -Infinity has the highest
       // 9 bits set and the lowest 23 bits cleared.
-      __ mov(ecx, 0xFF800000u);
-      __ movd(xmm4, ecx);
-      __ cvtss2sd(xmm4, xmm4);
-      __ ucomisd(xmm1, xmm4);
+      __ mov(scratch, 0xFF800000u);
+      __ movd(double_scratch, scratch);
+      __ cvtss2sd(double_scratch, double_scratch);
+      __ ucomisd(double_base, double_scratch);
       // Comparing -Infinity with NaN results in "unordered", which sets the
       // zero flag as if both were equal.  However, it also sets the carry flag.
       __ j(not_equal, &continue_rsqrt, Label::kNear);
       __ j(carry, &continue_rsqrt, Label::kNear);
 
       // Set result to 0 in the special case.
-      __ xorps(xmm3, xmm3);
+      __ xorps(double_result, double_result);
       __ jmp(&done);
 
       __ bind(&continue_rsqrt);
       // sqrtsd returns -0 when input is -0.  ECMA spec requires +0.
-      __ xorps(xmm2, xmm2);
-      __ addsd(xmm2, xmm1);  // Convert -0 to +0.
-      __ sqrtsd(xmm2, xmm2);
-      __ divsd(xmm3, xmm2);
+      __ xorps(double_exponent, double_exponent);
+      __ addsd(double_exponent, double_base);  // Convert -0 to +0.
+      __ sqrtsd(double_exponent, double_exponent);
+      __ divsd(double_result, double_exponent);
       __ jmp(&done);
     }
 
@@ -3080,9 +3087,9 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ fnclex();  // Clear flags to catch exceptions later.
     // Transfer (B)ase and (E)xponent onto the FPU register stack.
     __ sub(esp, Immediate(kDoubleSize));
-    __ movdbl(Operand(esp, 0), xmm2);
+    __ movdbl(Operand(esp, 0), double_exponent);
     __ fld_d(Operand(esp, 0));  // E
-    __ movdbl(Operand(esp, 0), xmm1);
+    __ movdbl(Operand(esp, 0), double_base);
     __ fld_d(Operand(esp, 0));  // B, E
 
     // Exponent is in st(1) and base is in st(0)
@@ -3102,10 +3109,10 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ fstp(1);
     // Bail out to runtime in case of exceptions in the status word.
     __ fnstsw_ax();
-    __ test_b(eax, 0x5F);  // We check for all but precision exception.
+    __ test_b(exponent, 0x5F);  // We check for all but precision exception.
     __ j(not_zero, &fast_power_failed, Label::kNear);
     __ fstp_d(Operand(esp, 0));
-    __ movdbl(xmm3, Operand(esp, 0));
+    __ movdbl(double_result, Operand(esp, 0));
     __ add(esp, Immediate(kDoubleSize));
     __ jmp(&done);
 
@@ -3117,49 +3124,46 @@ void MathPowStub::Generate(MacroAssembler* masm) {
 
   // Calculate power with integer exponent.
   __ bind(&int_exponent);
-  // xmm1: base as double that is not +/- Infinity or NaN
-  // eax: exponent as untagged integer
-  __ mov(ecx, eax);      // Back up exponent.
-  __ movsd(xmm4, xmm1);  // Back up base.
-  __ movsd(xmm2, xmm3);  // Load xmm2 with 1.
-
+  const XMMRegister double_scratch2 = double_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 no_neg, while_true, no_multiply;
-  __ cmp(eax, 0);
+  __ cmp(exponent, 0);
   __ j(greater_equal, &no_neg, Label::kNear);
-  __ neg(eax);
+  __ neg(exponent);
   __ bind(&no_neg);
 
   __ bind(&while_true);
-  __ shr(eax, 1);
+  __ shr(exponent, 1);
   __ j(not_carry, &no_multiply, Label::kNear);
-  __ mulsd(xmm3, xmm1);
+  __ mulsd(double_result, double_base);
   __ bind(&no_multiply);
 
-  __ mulsd(xmm1, xmm1);
+  __ mulsd(double_base, double_base);
   __ j(not_zero, &while_true);
 
-  // base has the original value of the exponent - if the exponent  is
-  // negative return 1/result.
-  __ test(ecx, ecx);
+  // scratch has the original value of the exponent - if the exponent is
+  // negative, return 1/result.
+  __ test(scratch, scratch);
   __ j(positive, &done);
-  __ divsd(xmm2, xmm3);
-  __ movsd(xmm3, xmm2);
+  __ divsd(double_scratch2, double_result);
+  __ movsd(double_result, double_scratch2);
   // Test whether result is zero.  Bail out to check for subnormal result.
   // Due to subnormals, x^-y == (1/x)^y does not hold in all cases.
-  __ xorps(xmm2, xmm2);
-  __ ucomisd(xmm2, xmm3);  // Result cannot be NaN.
+  __ xorps(double_scratch2, double_scratch2);
+  __ ucomisd(double_scratch2, double_result);  // Result cannot be NaN.
   __ j(equal, &double_int_runtime);
 
   // Returning or bailing out.
   if (exponent_type_ == ON_STACK) {
     // The stub is called from non-optimized code, which expects the result
-    // as heap number in eax.
+    // as heap number in exponent.
     __ bind(&done);
-    // xmm3: result
-    __ AllocateHeapNumber(eax, ecx, edx, &generic_runtime);
-    __ movdbl(FieldOperand(eax, HeapNumber::kValueOffset), xmm3);
+    __ AllocateHeapNumber(exponent, scratch, base, &generic_runtime);
+    __ movdbl(FieldOperand(exponent, HeapNumber::kValueOffset), double_result);
     __ ret(2 * kPointerSize);
 
     // The arguments are still on the stack.
@@ -3170,28 +3174,23 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     __ jmp(&done);
 
     Label return_from_runtime;
-    StubRuntimeCallHelper callhelper;
     __ bind(&generic_runtime);
-    // xmm1: base
-    // xmm2: exponent
     {
       AllowExternalCallThatCantCauseGC scope(masm);
-      __ PrepareCallCFunction(4, eax);
-      __ movdbl(Operand(esp, 0 * kDoubleSize), xmm1);
-      __ movdbl(Operand(esp, 1 * kDoubleSize), xmm2);
+      __ PrepareCallCFunction(4, exponent);
+      __ 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);
-    // xmm4: base
-    // ecx: exponent
     {
       AllowExternalCallThatCantCauseGC scope(masm);
-      __ PrepareCallCFunction(4, eax);
-      __ movdbl(Operand(esp, 0 * kDoubleSize), xmm4);
-      __ mov(Operand(esp, 1 * kDoubleSize), ecx);
+      __ 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);
     }
@@ -3201,10 +3200,9 @@ void MathPowStub::Generate(MacroAssembler* masm) {
     // Store it into the (fixed) result register.
     __ sub(esp, Immediate(kDoubleSize));
     __ fstp_d(Operand(esp, 0));
-    __ movdbl(xmm3, Operand(esp, 0));
+    __ movdbl(double_result, Operand(esp, 0));
     __ add(esp, Immediate(kDoubleSize));
 
-    // xmm3: result
     __ bind(&done);
     __ ret(0);
   }