Bug 346476

Summary:	vex amd64->IR: unhandled instruction bytes: 0xC5 0xFD 0xC2 0xC1 0x10 0xC5 0xFD 0x29
Product:	[Developer tools] valgrind	Reporter:	Peter van Hoof <pvh>
Component:	memcheck	Assignee:	Julian Seward <jseward>
Status:	RESOLVED DUPLICATE
Severity:	crash
Priority:	NOR
Version:	3.10.0
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed In:
Attachments:	test case simplified test case

Description Peter van Hoof 2015-04-22 16:16:50 UTC

The attached program runs fine on my Intel Core i7-3930K, but when I run it through memcheck, I get a complaint about an illegal instruction. This happens on this line:

v4df zmask = _mm256_cmp_pd(xarg, zero, _CMP_EQ_OS);

The interesting detail is that this is not the first instance of _mm256_cmp_pd(), but the second...

Reproducible: Always

Steps to Reproduce:
1. compile with "g++ -mavx bug.cpp"
2. run with "valgrind a.out" (obviously on AVX capable hardware)


Actual Results:  
==24621== Memcheck, a memory error detector
==24621== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==24621== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info
==24621== Command: a.out
==24621== 
vex amd64->IR: unhandled instruction bytes: 0xC5 0xFD 0xC2 0xC1 0x10 0xC5 0xFD 0x29
vex amd64->IR:   REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0
vex amd64->IR:   VEX=1 VEX.L=1 VEX.nVVVV=0x0 ESC=0F
vex amd64->IR:   PFX.66=1 PFX.F2=0 PFX.F3=0
==24621== valgrind: Unrecognised instruction at address 0x401256.
==24621==    at 0x401256: v1logd(double __vector(4)) (bug.cpp:107)
==24621==    by 0x4005F6: main (bug.cpp:121)
... etc ...

Expected Results:  
A run with no complaints.

OS : openSUSE 13.2 64-bit
g++ : g++ (SUSE Linux) 4.8.3 20140627 [gcc-4_8-branch revision 212064]

Comment 1 Peter van Hoof 2015-04-22 16:17:33 UTC

Created attachment 92163 [details]
test case

Comment 2 Peter van Hoof 2015-05-14 03:27:30 UTC

Further testing shows that the failure depends on the value of the compare predicate. The following predicates fail:

_CMP_FALSE_OQ
_CMP_TRUE_UQ
_CMP_EQ_OS
_CMP_UNORD_S
_CMP_NEQ_US
_CMP_NLT_UQ
_CMP_ORD_S
_CMP_EQ_US
_CMP_NGE_UQ
_CMP_NGT_UQ
_CMP_FALSE_OS
_CMP_NEQ_OS
_CMP_GE_OQ
_CMP_TRUE_US

The rest works fine. This explains why only the second instance of _mm256_cmp_pd() failed.

Comment 3 Peter van Hoof 2015-05-14 04:24:06 UTC

Based on this I created a simplified test case bug2.cpp

Steps to Reproduce:
1. compile with "g++ -mavx bug.cpp"
2. run with "valgrind a.out <n>"

where <n> is the numeric value of the compare predicate (between 0 and 31).

Comment 4 Peter van Hoof 2015-05-14 04:25:19 UTC

Created attachment 92589 [details]
simplified test case

Comment 5 Julian Seward 2015-08-13 12:50:59 UTC

Fixed, vex r3170.

*** This bug has been marked as a duplicate of bug 342571 ***