ARM64: Move sign-extension to load instructions.
The SXTW extend mode is usually free when used in a load or store
operand, but it can slightly increase the latency of an arithmetic
instruction. This patch optimises some address calculations accordingly:
- PrepareKeyedExternalArrayOperand.
- BuildSeqStringOperand.
- DoStringCharFromCode.
BUG=
R=ulan@chromium.org
Review URL: https://codereview.chromium.org/
247443002
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20891
ce2b1a6d-e550-0410-aec6-
3dcde31c8c00