602873 - Code mis-compiled by VS2008 -favor:INTEL64 switch

Status: RESOLVED INVALID

(Core :: JavaScript Engine, defect)

Description

[Steve Snyder]

64-bit VS2008/SP1 mis-compiles (Firefox 4.0b6) source file jsinterp.cpp when the -favor:INTEL64 switch is used.  The symptom is a runtime protection fault in DefaultValue() when a pointer has a bogus value.  Omission of this switch results in a working build.

This behavior is true with optimization levels -O1 or -O2, and with debug symbols enabled or disabled.

FYI, the compiler default is -favor:blend.  Options INTEL64 or AMD64 are said to provide better code gen for 64-bit CPUs from their respective vendors.

Comment 1

[Steve Snyder]

Attachment: Filter out -favor:INTEL64 switch from jsinterp.obj build

Patch is conditional on compiler being VS2008.  No test is done for x86_64 platform because the switch is only defined for 64-bit compilers.

Comment 2

[Steve Snyder]

Attachment: ZIP archive: ASM code generated with and without switch

I'm not certain exactly what generated code causes the faults, i.e. what bad code results from the -favor:INTEL64 switch.  I suspect it's associated with lost sign bits.

For the morbidly curious, this ZIP file contains the VS2008/SP1 ASM output for jsinterp.cpp compilation, both with and without the troublesome switch.  There's actually not a lot of difference between the 2 files.

Comment 3

[Jan de Mooij [:jandem]]

VS2008 is no longer supported.