Reviewers: Erik Corry,
Description:
ARM: Special case for modulus of two smis in the generic binary opration
stub
When lhs and rhs are positive smis and rhs is a power of two perform
modulus by
masking.
Please review this at http://codereview.chromium.org/2873001/show
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/arm/codegen-arm.cc
Index: src/arm/codegen-arm.cc
===================================================================
--- src/arm/codegen-arm.cc (revision 4874)
+++ src/arm/codegen-arm.cc (working copy)
@@ -8164,6 +8164,28 @@
}
__ Ret();
__ bind(&smi_is_unsuitable);
+ } else if (op_ == Token::MOD &&
+ runtime_operands_type_ != BinaryOpIC::HEAP_NUMBERS &&
+ runtime_operands_type_ != BinaryOpIC::STRINGS) {
+ // Do generate a bit of smi code for modulus even though the
default for
+ // modulus is not to do it, but as the ARM processor has no
coprocessor
+ // support for modulus checking for smis makes sense.
+ Label slow;
+ ASSERT(!ShouldGenerateSmiCode());
+ ASSERT(kSmiTag == 0); // Adjust code below.
+ // Check for two positive smis.
+ __ orr(smi_test_reg, lhs, Operand(rhs));
+ __ tst(smi_test_reg, Operand(0x80000000u | kSmiTagMask));
+ __ b(ne, &slow);
+ // Check that rhs is a power of two and not zero.
+ __ sub(scratch, rhs, Operand(1), SetCC);
+ __ b(mi, &slow);
+ __ tst(rhs, scratch);
+ __ b(ne, &slow);
+ // Calculate power of two modulus.
+ __ and_(result, lhs, Operand(scratch));
+ __ Ret();
+ __ bind(&slow);
}
HandleBinaryOpSlowCases(
masm,
--
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