MacroAssemblerX86 8-bit register ops unsafe on CPU(X86)

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Gavin Barraclough]

Certain ops are unsafe if the register passed is esp..edi (will instead test/set the ).

compare32/test8/test32 Call setCC, which sets an 8-bit register - we can fix this by adding a couple of xchg instructions.

branchTest8 with a register argument is also affected.  In all cases this is currently used this is testing a value that is correct to 32 or more bits, so we can simply switch these to branchTest32 & remove the corresponding branchTest8 (this is desirable anyway, since the 32-bit form is cheaper to implement on platforms that don't have an 8-bit compare instruction).

This fixes the remaining fast/js failures with the DFG JIT 32_64.

[Gavin Barraclough]

Created attachment 110773 [details]
The fix

[WebKit Review Bot]

Attachment 110773 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/JavaScriptCore/ChangeLog', u'Source..." exit_code: 1

Source/JavaScriptCore/ChangeLog:20:  Need whitespace between colon and description  [changelog/filechangedescriptionwhitespace] [5]
Total errors found: 1 in 6 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Gavin Barraclough]

Fixed in r97331