Issue 4321: Remove x86 jump elimination.

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Issue 4321: Remove x86 jump elimination. (Closed)

Created:
12 years, 2 months ago by Dean McNamee

Modified:
9 years, 7 months ago

Reviewers:
iposva, Kasper Lund

CC:
v8-dev

Visibility:
Public.

Description

Remove x86 jump elimination. This was just complicated enough to make it annoying to support short jump encoding. I measured a code size increase of 5 bytes on the V8 benchmark, from missing one jump to next elimination possibility.

Patch Set 1 #

Created: 12 years, 2 months ago

Download [raw] [tar.bz2]

		Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+0 lines, -69 lines)			Patch
	M	src/assembler-ia32.h	View		1 chunk	+0 lines, -8 lines	0 comments	Download
	M	src/assembler-ia32.cc	View		5 chunks	+0 lines, -61 lines	0 comments	Download

Messages

Total messages: 1 (0 generated)

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Dean McNamee

12 years, 2 months ago (2008-09-28 13:07:46 UTC) #1

I realize I should probably look at ARM also, remove the jump elimination flag
all together, or make it ARM specific.  I just wanted to wait until I got some
initial feedback, maybe you think this is a bad idea.

The single jump that was being eliminated with this current code was in the fast
switch code.  I didn't track it down all the way, but it might be easy to fix
statically.  Otherwise, it's not a huge deal, we're going to save a lot more
than 5 bytes with short jumps.

I could try to keep the code and make it work with short jump encoding.  It just
seemed to be a lot of complexity for hardly ever saving a few bytes at most in
my experiments.

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