Issue 211383008: Refine a bit ClampXToUint8

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Issue 211383008: Refine a bit ClampXToUint8 (Closed)

Created:
6 years, 9 months ago by Weiliang

Modified:
6 years, 2 months ago

Reviewers:
danno, Jakob Kummerow

CC:
v8-dev

Base URL:
git://github.com/v8/v8.git@master

Visibility:
Public.

More Reviews

Description

Refactor a bit ClampXToUint8 BUG=

Patch Set 1 #

Created: 6 years, 9 months ago

Download [raw] [tar.bz2]

		Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+14 lines, -18 lines)			Patch
	M	src/ia32/macro-assembler-ia32.cc	View		2 chunks	+7 lines, -9 lines	0 comments	Download
	M	src/x64/macro-assembler-x64.cc	View		2 chunks	+7 lines, -9 lines	0 comments	Download

Messages

Total messages: 1 (0 generated)

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Weiliang

6 years, 9 months ago (2014-03-26 03:20:42 UTC) #1

As previous discuss, I split the refine of ClampXToUint8 into a separate CL. 

Currently the change seems to be safe. Actually the original version in
ClampToUint8 also leaves the high bit unchanged like below and only the low byte
change leads to false data dependency.  
setcc(negative, reg);  // 1 if negative, 0 if positive.
dec_b(reg);  // 0 if negative, 255 if positive.

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