Revision: 10172
Author: [email protected]
Date: Tue Dec 6 03:56:56 2011
Log: Remove early NaN/Infinity check in MathPowStub.
Review URL: http://codereview.chromium.org/8817015
http://code.google.com/p/v8/source/detail?r=10172
Modified:
/branches/bleeding_edge/src/assembler.cc
/branches/bleeding_edge/src/ia32/code-stubs-ia32.cc
/branches/bleeding_edge/src/runtime.cc
=======================================
--- /branches/bleeding_edge/src/assembler.cc Mon Dec 5 01:54:15 2011
+++ /branches/bleeding_edge/src/assembler.cc Tue Dec 6 03:56:56 2011
@@ -1124,8 +1124,6 @@
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);
}
-#else
- if (y == 0) return 1.0; // Returns 1.0 for exponent 0.
#endif
if (isnan(y) || ((x == 1 || x == -1) && isinf(y))) {
return OS::nan_value();
=======================================
--- /branches/bleeding_edge/src/ia32/code-stubs-ia32.cc Tue Dec 6 01:20:28
2011
+++ /branches/bleeding_edge/src/ia32/code-stubs-ia32.cc Tue Dec 6 03:56:56
2011
@@ -2946,74 +2946,49 @@
__ mov(ecx, Immediate(1));
__ cvtsi2sd(xmm3, ecx);
- switch (exponent_type_) {
- case ON_STACK:
- // 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),
- factory->heap_number_map());
- __ j(not_equal, &generic_runtime);
-
- // Check base for NaN or +/-Infinity
- __ mov(ecx, FieldOperand(edx, HeapNumber::kExponentOffset));
- __ and_(ecx, HeapNumber::kExponentMask);
- __ cmp(ecx, Immediate(HeapNumber::kExponentMask));
- __ j(equal, &generic_runtime);
- __ movdbl(xmm1, FieldOperand(edx, HeapNumber::kValueOffset));
- __ jmp(&unpack_exponent, Label::kNear);
-
- __ bind(&base_is_smi);
- __ SmiUntag(edx);
- __ cvtsi2sd(xmm1, edx);
- __ bind(&unpack_exponent);
-
- __ JumpIfNotSmi(eax, &exponent_not_smi, Label::kNear);
- __ SmiUntag(eax);
- __ jmp(&int_exponent);
-
- __ bind(&exponent_not_smi);
- __ cmp(FieldOperand(eax, HeapObject::kMapOffset),
- factory->heap_number_map());
- __ j(not_equal, &generic_runtime);
- __ movdbl(xmm2, FieldOperand(eax, HeapNumber::kValueOffset));
- break;
-
- case TAGGED:
- // xmm1: base as double
- // eax: exponent (smi or heap number)
- __ JumpIfNotSmi(eax, &exponent_not_smi, Label::kNear);
- __ SmiUntag(eax);
- __ jmp(&int_exponent);
-
- __ bind(&exponent_not_smi);
- __ movdbl(xmm2, FieldOperand(eax, HeapNumber::kValueOffset));
- // Fall through intended
- case INTEGER:
- // xmm1: base as double
- // eax: exponent as untagged integer
- case DOUBLE:
- // xmm1: base as double
- // xmm2: exponent as double
- // Check base in xmm1 for NaN or +/-Infinity
- const int kExponentShift = kBitsPerByte *
- (HeapNumber::kExponentOffset - HeapNumber::kMantissaOffset);
- __ movsd(xmm4, xmm1);
- __ psrlq(xmm4, kExponentShift);
- __ movd(ecx, xmm4);
- __ and_(ecx, HeapNumber::kExponentMask);
- __ cmp(ecx, Immediate(HeapNumber::kExponentMask));
- __ j(equal, &generic_runtime);
- break;
+ if (exponent_type_ == ON_STACK) {
+ // 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),
+ factory->heap_number_map());
+ __ j(not_equal, &generic_runtime);
+
+ __ movdbl(xmm1, FieldOperand(edx, HeapNumber::kValueOffset));
+ __ jmp(&unpack_exponent, Label::kNear);
+
+ __ bind(&base_is_smi);
+ __ SmiUntag(edx);
+ __ cvtsi2sd(xmm1, edx);
+ __ bind(&unpack_exponent);
+
+ __ JumpIfNotSmi(eax, &exponent_not_smi, Label::kNear);
+ __ SmiUntag(eax);
+ __ jmp(&int_exponent);
+
+ __ bind(&exponent_not_smi);
+ __ cmp(FieldOperand(eax, HeapObject::kMapOffset),
+ factory->heap_number_map());
+ __ j(not_equal, &generic_runtime);
+ __ movdbl(xmm2, FieldOperand(eax, 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);
+ __ jmp(&int_exponent);
+
+ __ bind(&exponent_not_smi);
+ __ movdbl(xmm2, FieldOperand(eax, HeapNumber::kValueOffset));
}
if (exponent_type_ != INTEGER) {
- Label not_minus_half, fast_power;
+ Label fast_power;
// xmm1: base as double that is not +/- Infinity or NaN
// xmm2: exponent as double
// Detect integer exponents stored as double.
@@ -3029,37 +3004,67 @@
// Detect square root case. Crankshaft detects constant +/-0.5 at
// compile time and uses DoMathPowHalf instead. We then skip this
check
// for non-constant cases of +/-0.5 as these hardly occur.
-
- // Test for -0.5.
- // Load xmm4 with -0.5.
- __ mov(ecx, Immediate(0xBF000000u));
+ 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);
- // xmm3 now has -0.5.
+ // xmm4 now has 0.5.
__ ucomisd(xmm4, xmm2);
- __ j(not_equal, ¬_minus_half, Label::kNear);
-
- // Calculates reciprocal of square root.eax
+ __ j(not_equal, ¬_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);
+ __ j(not_equal, &continue_sqrt, Label::kNear);
+
+ // Set result to Infinity in the special case.
+ __ xorps(xmm3, xmm3);
+ __ subsd(xmm3, xmm4);
+ __ jmp(&done);
+
+ __ bind(&continue_sqrt);
// sqrtsd returns -0 when input is -0. ECMA spec requires +0.
- __ xorps(xmm2, xmm2);
- __ addsd(xmm2, xmm1);
- __ sqrtsd(xmm2, xmm2);
- __ divsd(xmm3, xmm2);
+ __ xorps(xmm4, xmm4);
+ __ addsd(xmm4, xmm1); // Convert -0 to +0.
+ __ sqrtsd(xmm3, xmm4);
__ jmp(&done);
- // Test for 0.5.
- __ bind(¬_minus_half);
- // Load xmm2 with 0.5.
- // Since xmm3 is 1 and xmm4 is -0.5 this is simply xmm4 + xmm3.
- __ addsd(xmm4, xmm3);
- // xmm2 now has 0.5.
+ // Test for -0.5.
+ __ bind(¬_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);
__ j(not_equal, &fast_power, Label::kNear);
- // Calculates square root.
+
+ // 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);
+ __ j(not_equal, &continue_rsqrt, Label::kNear);
+
+ // Set result to 0 in the special case.
+ __ xorps(xmm3, xmm3);
+ __ jmp(&done);
+
+ __ bind(&continue_rsqrt);
// sqrtsd returns -0 when input is -0. ECMA spec requires +0.
- __ xorps(xmm4, xmm4);
- __ addsd(xmm4, xmm1);
- __ sqrtsd(xmm3, xmm4);
+ __ xorps(xmm2, xmm2);
+ __ addsd(xmm2, xmm1); // Convert -0 to +0.
+ __ sqrtsd(xmm2, xmm2);
+ __ divsd(xmm3, xmm2);
__ jmp(&done);
}
=======================================
--- /branches/bleeding_edge/src/runtime.cc Fri Dec 2 04:42:35 2011
+++ /branches/bleeding_edge/src/runtime.cc Tue Dec 6 03:56:56 2011
@@ -7414,6 +7414,9 @@
}
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));
}
--
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