Correct bug with left shift on X64 platform from change 4571 (http://code.goo...

Correct bug with left shift on X64 platform from change 4571 (http://code.google.com/p/v8/source/detail?r=4571).  Speed up left shift with a constant left hand side on X64 platform.  Add unit test for this bug.  Remove unused failure target argument from MacroAssembler::SmiShiftLeft and MacroAssembler::SmiShiftLeftConstant.

Committed: http://code.google.com/p/v8/source/detail?r=4598

[fschneider, 2010-05-05 16:30:27]

LGTM.

http://codereview.chromium.org/1934004/diff/7001/8002
File src/x64/codegen-x64.cc (right):

http://codereview.chromium.org/1934004/diff/7001/8002#newcode6558
src/x64/codegen-x64.cc:6558: __ SmiShiftLeft(answer.reg(), answer.reg(),
operand->reg(), NULL);
The last parameter (Label*) is never used in the macro assembler. You could
eliminate it completely.

[Lasse Reichstein, 2010-05-05 17:21:33]

http://codereview.chromium.org/1934004/diff/7001/8002
File src/x64/codegen-x64.cc (right):

http://codereview.chromium.org/1934004/diff/7001/8002#newcode6558
src/x64/codegen-x64.cc:6558: __ SmiShiftLeft(answer.reg(), answer.reg(),
operand->reg(), NULL);
Correct, it's a leftover from when smis were 31 bits, so the operation could
overflow. We are unlikely to ever go back to less than 32 bits again, so it
should be safe to remove.

[William Hesse, 2010-05-06 07:29:31]

Lasse's suggestions incorporated: unused argument to SmiShiftLeft{|Constant}
removed.

[Lasse Reichstein, 2010-05-06 08:00:35]

Last changes LGTM, haven't re-reviewed what Florian LGTM'ed.