Issue 9723: Use shorter SIB encoding.

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Issue 9723: Use shorter SIB encoding. (Closed)

Created:
12 years, 1 month ago by Dean McNamee

Modified:
9 years, 7 months ago

Reviewers:
Kasper Lund

CC:
v8-dev

Visibility:
Public.

Description

Use shorter SIB encoding. For example, the previous: 8d044500000000 lea eax,[eax*2+0x0] Will be encoded with the much shorter: 8d0400 lea eax,[eax+eax*1]

Patch Set 1 #

Patch Set 2 : Drop unwanted changes to other files #

Created: 12 years, 1 month ago

Download [raw] [tar.bz2]

		Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+6 lines, -6 lines)			Patch
	M	src/codegen-ia32.cc	View		6 chunks	+6 lines, -6 lines	0 comments	Download

Messages

Total messages: 1 (0 generated)

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Dean McNamee

12 years, 1 month ago (2008-11-08 01:58:41 UTC) #1

Originally I had changed Operand to make this optimization when scale = times_2,
but I don't really like the idea of having lots of optimizations in the
assembler, so you can't get specific encodings if you wanted them.

Adam pointed out that lea eax,[eax+eax*1] should still be shorter as shl eax, 1,
which just happens because kSmiTag is 0.  I don't know if it's worth trying to
handle that case somehow.

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