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Small optimization of ARM compare stub. Reverse all references to

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left and right sides of the comparison to reflect reality.  Don't
check explicitly for NaNs when using VFP3 since the compare
operation can signal this case with the v flag.  Use cmp instead
of tst in the fast compilers since tst leaves the v flag unchanged
and thus can only work by accident on non-equality comparisons.
Review URL: http://codereview.chromium.org/551048

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3625 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
erik.corry@gmail.com 2010-01-18 08:36:06 +00:00
parent 6d7ce68102
commit a5ac66628d
4 changed files with 83 additions and 59 deletions
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120
src/arm/codegen-arm.cc
View File

@ -47,7 +47,7 @@ static void EmitIdenticalObjectComparison(MacroAssembler* masm,
Condition cc,
bool never_nan_nan);
static void EmitSmiNonsmiComparison(MacroAssembler* masm,
Label* rhs_not_nan,
Label* lhs_not_nan,
Label* slow,
bool strict);
static void EmitTwoNonNanDoubleComparison(MacroAssembler* masm, Condition cc);
@ -4778,7 +4778,7 @@ static void EmitIdenticalObjectComparison(MacroAssembler* masm,
} else if (cc == gt) {
__ mov(r0, Operand(LESS)); // Things aren't greater than themselves.
} else {
__ mov(r0, Operand(0)); // Things are <=, >=, ==, === themselves.
__ mov(r0, Operand(EQUAL)); // Things are <=, >=, ==, === themselves.
}
__ mov(pc, Operand(lr)); // Return.
@ -4790,6 +4790,7 @@ static void EmitIdenticalObjectComparison(MacroAssembler* masm,
__ bind(&heap_number);
// It is a heap number, so return non-equal if it's NaN and equal if it's
// not NaN.
// The representation of NaN values has all exponent bits (52..62) set,
// and not all mantissa bits (0..51) clear.
// Read top bits of double representation (second word of value).
@ -4805,9 +4806,9 @@ static void EmitIdenticalObjectComparison(MacroAssembler* masm,
__ ldr(r3, FieldMemOperand(r0, HeapNumber::kMantissaOffset));
__ orr(r0, r3, Operand(r2), SetCC);
// For equal we already have the right value in r0: Return zero (equal)
// if all bits in mantissa are zero (it's an Infinity) and non-zero if not
// (it's a NaN). For <= and >= we need to load r0 with the failing value
// if it's a NaN.
// if all bits in mantissa are zero (it's an Infinity) and non-zero if
// not (it's a NaN). For <= and >= we need to load r0 with the failing
// value if it's a NaN.
if (cc != eq) {
// All-zero means Infinity means equal.
__ mov(pc, Operand(lr), LeaveCC, eq); // Return equal
@ -4828,7 +4829,7 @@ static void EmitIdenticalObjectComparison(MacroAssembler* masm,
// See comment at call site.
static void EmitSmiNonsmiComparison(MacroAssembler* masm,
Label* rhs_not_nan,
Label* lhs_not_nan,
Label* slow,
bool strict) {
Label lhs_is_smi;
@ -4866,7 +4867,7 @@ static void EmitSmiNonsmiComparison(MacroAssembler* masm,
// We now have both loaded as doubles but we can skip the lhs nan check
// since it's a Smi.
__ pop(lr);
__ jmp(rhs_not_nan);
__ jmp(lhs_not_nan);
__ bind(&lhs_is_smi);
// Lhs is a Smi. Check whether the non-smi is a heap number.
@ -4902,37 +4903,39 @@ static void EmitSmiNonsmiComparison(MacroAssembler* masm,
}
void EmitNanCheck(MacroAssembler* masm, Label* rhs_not_nan, Condition cc) {
void EmitNanCheck(MacroAssembler* masm, Label* lhs_not_nan, Condition cc) {
bool exp_first = (HeapNumber::kExponentOffset == HeapNumber::kValueOffset);
Register lhs_exponent = exp_first ? r0 : r1;
Register rhs_exponent = exp_first ? r2 : r3;
Register lhs_mantissa = exp_first ? r1 : r0;
Register rhs_mantissa = exp_first ? r3 : r2;
Register rhs_exponent = exp_first ? r0 : r1;
Register lhs_exponent = exp_first ? r2 : r3;
Register rhs_mantissa = exp_first ? r1 : r0;
Register lhs_mantissa = exp_first ? r3 : r2;
Label one_is_nan, neither_is_nan;
Label lhs_not_nan_exp_mask_is_loaded;
Register exp_mask_reg = r5;
__ mov(exp_mask_reg, Operand(HeapNumber::kExponentMask));
__ and_(r4, rhs_exponent, Operand(exp_mask_reg));
__ cmp(r4, Operand(exp_mask_reg));
__ b(ne, rhs_not_nan);
__ mov(r4,
Operand(rhs_exponent, LSL, HeapNumber::kNonMantissaBitsInTopWord),
SetCC);
__ b(ne, &one_is_nan);
__ cmp(rhs_mantissa, Operand(0));
__ b(ne, &one_is_nan);
__ bind(rhs_not_nan);
__ mov(exp_mask_reg, Operand(HeapNumber::kExponentMask));
__ and_(r4, lhs_exponent, Operand(exp_mask_reg));
__ cmp(r4, Operand(exp_mask_reg));
__ b(ne, &neither_is_nan);
__ b(ne, &lhs_not_nan_exp_mask_is_loaded);
__ mov(r4,
Operand(lhs_exponent, LSL, HeapNumber::kNonMantissaBitsInTopWord),
SetCC);
__ b(ne, &one_is_nan);
__ cmp(lhs_mantissa, Operand(0));
__ b(ne, &one_is_nan);
__ bind(lhs_not_nan);
__ mov(exp_mask_reg, Operand(HeapNumber::kExponentMask));
__ bind(&lhs_not_nan_exp_mask_is_loaded);
__ and_(r4, rhs_exponent, Operand(exp_mask_reg));
__ cmp(r4, Operand(exp_mask_reg));
__ b(ne, &neither_is_nan);
__ mov(r4,
Operand(rhs_exponent, LSL, HeapNumber::kNonMantissaBitsInTopWord),
SetCC);
__ b(ne, &one_is_nan);
__ cmp(rhs_mantissa, Operand(0));
__ b(eq, &neither_is_nan);
__ bind(&one_is_nan);
@ -4952,21 +4955,21 @@ void EmitNanCheck(MacroAssembler* masm, Label* rhs_not_nan, Condition cc) {
// See comment at call site.
static void EmitTwoNonNanDoubleComparison(MacroAssembler* masm, Condition cc) {
bool exp_first = (HeapNumber::kExponentOffset == HeapNumber::kValueOffset);
Register lhs_exponent = exp_first ? r0 : r1;
Register rhs_exponent = exp_first ? r2 : r3;
Register lhs_mantissa = exp_first ? r1 : r0;
Register rhs_mantissa = exp_first ? r3 : r2;
Register rhs_exponent = exp_first ? r0 : r1;
Register lhs_exponent = exp_first ? r2 : r3;
Register rhs_mantissa = exp_first ? r1 : r0;
Register lhs_mantissa = exp_first ? r3 : r2;
// r0, r1, r2, r3 have the two doubles. Neither is a NaN.
if (cc == eq) {
// Doubles are not equal unless they have the same bit pattern.
// Exception: 0 and -0.
__ cmp(lhs_mantissa, Operand(rhs_mantissa));
__ orr(r0, lhs_mantissa, Operand(rhs_mantissa), LeaveCC, ne);
__ cmp(rhs_mantissa, Operand(lhs_mantissa));
__ orr(r0, rhs_mantissa, Operand(lhs_mantissa), LeaveCC, ne);
// Return non-zero if the numbers are unequal.
__ mov(pc, Operand(lr), LeaveCC, ne);
__ sub(r0, lhs_exponent, Operand(rhs_exponent), SetCC);
__ sub(r0, rhs_exponent, Operand(lhs_exponent), SetCC);
// If exponents are equal then return 0.
__ mov(pc, Operand(lr), LeaveCC, eq);
@ -4976,12 +4979,12 @@ static void EmitTwoNonNanDoubleComparison(MacroAssembler* masm, Condition cc) {
// We start by seeing if the mantissas (that are equal) or the bottom
// 31 bits of the rhs exponent are non-zero. If so we return not
// equal.
__ orr(r4, rhs_mantissa, Operand(rhs_exponent, LSL, kSmiTagSize), SetCC);
__ orr(r4, lhs_mantissa, Operand(lhs_exponent, LSL, kSmiTagSize), SetCC);
__ mov(r0, Operand(r4), LeaveCC, ne);
__ mov(pc, Operand(lr), LeaveCC, ne); // Return conditionally.
// Now they are equal if and only if the lhs exponent is zero in its
// low 31 bits.
__ mov(r0, Operand(lhs_exponent, LSL, kSmiTagSize));
__ mov(r0, Operand(rhs_exponent, LSL, kSmiTagSize));
__ mov(pc, Operand(lr));
} else {
// Call a native function to do a comparison between two non-NaNs.
@ -5036,9 +5039,10 @@ static void EmitCheckForTwoHeapNumbers(MacroAssembler* masm,
Label* both_loaded_as_doubles,
Label* not_heap_numbers,
Label* slow) {
__ CompareObjectType(r0, r2, r2, HEAP_NUMBER_TYPE);
__ CompareObjectType(r0, r3, r2, HEAP_NUMBER_TYPE);
__ b(ne, not_heap_numbers);
__ CompareObjectType(r1, r3, r3, HEAP_NUMBER_TYPE);
__ ldr(r2, FieldMemOperand(r1, HeapObject::kMapOffset));
__ cmp(r2, r3);
__ b(ne, slow); // First was a heap number, second wasn't. Go slow case.
// Both are heap numbers. Load them up then jump to the code we have
@ -5075,7 +5079,7 @@ static void EmitCheckForSymbols(MacroAssembler* masm, Label* slow) {
// positive or negative to indicate the result of the comparison.
void CompareStub::Generate(MacroAssembler* masm) {
Label slow; // Call builtin.
Label not_smis, both_loaded_as_doubles, rhs_not_nan;
Label not_smis, both_loaded_as_doubles, lhs_not_nan;
// NOTICE! This code is only reached after a smi-fast-case check, so
// it is certain that at least one operand isn't a smi.
@ -5095,32 +5099,46 @@ void CompareStub::Generate(MacroAssembler* masm) {
// 1) Return the answer.
// 2) Go to slow.
// 3) Fall through to both_loaded_as_doubles.
// 4) Jump to rhs_not_nan.
// 4) Jump to lhs_not_nan.
// In cases 3 and 4 we have found out we were dealing with a number-number
// comparison and the numbers have been loaded into r0, r1, r2, r3 as doubles.
EmitSmiNonsmiComparison(masm, &rhs_not_nan, &slow, strict_);
EmitSmiNonsmiComparison(masm, &lhs_not_nan, &slow, strict_);
__ bind(&both_loaded_as_doubles);
// r0, r1, r2, r3 are the double representations of the left hand side
// and the right hand side.
// Checks for NaN in the doubles we have loaded. Can return the answer or
// fall through if neither is a NaN. Also binds rhs_not_nan.
EmitNanCheck(masm, &rhs_not_nan, cc_);
// r0, r1, r2, r3 are the double representations of the right hand side
// and the left hand side.
if (CpuFeatures::IsSupported(VFP3)) {
__ bind(&lhs_not_nan);
CpuFeatures::Scope scope(VFP3);
Label no_nan;
// ARMv7 VFP3 instructions to implement double precision comparison.
__ vmov(d6, r0, r1);
__ vmov(d7, r2, r3);
__ vcmp(d6, d7);
__ vmrs(pc);
__ mov(r0, Operand(0), LeaveCC, eq);
__ mov(r0, Operand(1), LeaveCC, lt);
__ mvn(r0, Operand(0), LeaveCC, gt);
__ vcmp(d7, d6);
__ vmrs(pc); // Move vector status bits to normal status bits.
Label nan;
__ b(vs, &nan);
__ mov(r0, Operand(EQUAL), LeaveCC, eq);
__ mov(r0, Operand(LESS), LeaveCC, lt);
__ mov(r0, Operand(GREATER), LeaveCC, gt);
__ mov(pc, Operand(lr));
__ bind(&nan);
// If one of the sides was a NaN then the v flag is set. Load r0 with
// whatever it takes to make the comparison fail, since comparisons with NaN
// always fail.
if (cc_ == lt || cc_ == le) {
__ mov(r0, Operand(GREATER));
} else {
__ mov(r0, Operand(LESS));
}
__ mov(pc, Operand(lr));
} else {
// Checks for NaN in the doubles we have loaded. Can return the answer or
// fall through if neither is a NaN. Also binds lhs_not_nan.
EmitNanCheck(masm, &lhs_not_nan, cc_);
// Compares two doubles in r0, r1, r2, r3 that are not NaNs. Returns the
// answer. Never falls through.
EmitTwoNonNanDoubleComparison(masm, cc_);
@ -5139,7 +5157,7 @@ void CompareStub::Generate(MacroAssembler* masm) {
// Check for heap-number-heap-number comparison. Can jump to slow case,
// or load both doubles into r0, r1, r2, r3 and jump to the code that handles
// that case. If the inputs are not doubles then jumps to check_for_symbols.
// In this case r2 will contain the type of r0.
// In this case r2 will contain the type of r0. Never falls through.
EmitCheckForTwoHeapNumbers(masm,
&both_loaded_as_doubles,
&check_for_symbols,

6
src/arm/fast-codegen-arm.cc
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@ -1592,13 +1592,13 @@ void FastCodeGenerator::VisitCompareOperation(CompareOperation* expr) {
__ pop(r1);
break;
case Token::GT:
// Reverse left and right sizes to obtain ECMA-262 conversion order.
// Reverse left and right sides to obtain ECMA-262 conversion order.
cc = lt;
__ pop(r1);
__ pop(r0);
break;
case Token::LTE:
// Reverse left and right sizes to obtain ECMA-262 conversion order.
// Reverse left and right sides to obtain ECMA-262 conversion order.
cc = ge;
__ pop(r1);
__ pop(r0);
@ -1627,7 +1627,7 @@ void FastCodeGenerator::VisitCompareOperation(CompareOperation* expr) {
__ bind(&slow_case);
CompareStub stub(cc, strict);
__ CallStub(&stub);
__ tst(r0, r0);
__ cmp(r0, Operand(0));
__ b(cc, if_true);
__ jmp(if_false);
}

7
src/arm/simulator-arm.cc
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@ -890,8 +890,13 @@ bool Simulator::OverflowFrom(int32_t alu_out,
// Support for VFP comparisons.
void Simulator::Compute_FPSCR_Flags(double val1, double val2) {
if (isnan(val1) || isnan(val2)) {
n_flag_FPSCR_ = false;
z_flag_FPSCR_ = false;
c_flag_FPSCR_ = true;
v_flag_FPSCR_ = true;
// All non-NaN cases.
if (val1 == val2) {
} else if (val1 == val2) {
n_flag_FPSCR_ = false;
z_flag_FPSCR_ = true;
c_flag_FPSCR_ = true;

9
src/assembler.cc
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@ -44,6 +44,7 @@
#include "regexp-stack.h"
#include "ast.h"
#include "regexp-macro-assembler.h"
#include "platform.h"
// Include native regexp-macro-assembler.
#ifdef V8_NATIVE_REGEXP
#if V8_TARGET_ARCH_IA32
@ -706,13 +707,13 @@ static double div_two_doubles(double x, double y) {
static double mod_two_doubles(double x, double y) {
return fmod(x, y);
return modulo(x, y);
}
static int native_compare_doubles(double x, double y) {
if (x == y) return 0;
return x < y ? 1 : -1;
static int native_compare_doubles(double y, double x) {
if (x == y) return EQUAL;
return x < y ? LESS : GREATER;
}