Author: whessev8
Date: Fri Jan 23 05:06:15 2009
New Revision: 1134
Modified:
branches/bleeding_edge/src/codegen-ia32.cc
Log:
Optimizes check for Smi range in the code generator.
The check whether a 32-bit signed integer is in the Smi
range is now Sign bit( value + 0x40000000 ) == 0,
done with a single cmp instruction.
Review URL: http://codereview.chromium.org/18710
Modified: branches/bleeding_edge/src/codegen-ia32.cc
==============================================================================
--- branches/bleeding_edge/src/codegen-ia32.cc (original)
+++ branches/bleeding_edge/src/codegen-ia32.cc Fri Jan 23 05:06:15 2009
@@ -1127,9 +1127,11 @@
__ j(not_zero, deferred->enter(), not_taken);
__ sar(ebx, kSmiTagSize);
__ shl(ebx, shift_value);
- __ lea(ecx, Operand(ebx, 0x40000000));
- __ test(ecx, Immediate(0x80000000));
- __ j(not_zero, deferred->enter(), not_taken);
+ // This is the Smi check for the shifted result.
+ // After signed subtraction of 0xc0000000, the valid
+ // Smis are positive.
+ __ cmp(ebx, 0xc0000000);
+ __ j(sign, deferred->enter(), not_taken);
// tag result and store it in TOS (eax)
ASSERT(kSmiTagSize == times_2); // adjust code if not the case
__ lea(eax, Operand(ebx, ebx, times_1, kSmiTag));
@@ -4274,9 +4276,8 @@
case Token::SHL:
__ shl(eax);
// Check that the *signed* result fits in a smi.
- __ lea(ecx, Operand(eax, 0x40000000));
- __ test(ecx, Immediate(0x80000000));
- __ j(not_zero, slow, not_taken);
+ __ cmp(eax, 0xc0000000);
+ __ j(sign, slow, not_taken);
break;
default:
UNREACHABLE();
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