https://bugs.kde.org/show_bug.cgi?id=411451
Bug ID: 411451
Summary: x86/amd64->IR of bt/btc/bts/btr with immediate clears
zero flag
Product: valgrind
Version: 3.15 SVN
Platform: unspecified
OS: unspecified
Status: REPORTED
Severity: minor
Priority: NOR
Component: vex
Assignee: jsew...@acm.org
Reporter: baumra...@outlook.com
Target Milestone: ---
Created attachment 122426
--> https://bugs.kde.org/attachment.cgi?id=122426&action=edit
c++ code to reproduce the issue
According to Intel's Instruction Set Reference A-Z
(https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf),
the instructions bt/btc/bts/btr leave the ZF unchanged.
However, in VEX/priv/guest_amd64_toIR.c:4016ff in function dis_Grp8_Imm
the ZF is cleared, unlike the implementation for bt/btc/bts/btr with
non-immediate argument
in VEX/priv/guest_amd64_toIR.c:8225ff in function dis_bt_G_E which conforms to
the Intel
specification.
Also it seems that the x86 implementation clears the ZF both for immediate and
non-immediate argument versions of the bt/btc/bts/btr instructions.
See the attached code to reproduce the issue:
baumratte@linux:~/tmp/valgrind-bug> g++ -omain main.cxx
baumratte@linux:~/tmp/valgrind-bug> ./main
result = 0 (expecting 0)
baumratte@linux:~/tmp/valgrind-bug> valgrind ./main
==29558== Memcheck, a memory error detector
==29558== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==29558== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==29558== Command: ./main
==29558==
result = -1 (expecting 0)
==29558==
==29558== HEAP SUMMARY:
==29558== in use at exit: 0 bytes in 0 blocks
==29558== total heap usage: 1 allocs, 1 frees, 72,704 bytes allocated
==29558==
==29558== All heap blocks were freed -- no leaks are possible
==29558==
==29558== For lists of detected and suppressed errors, rerun with: -s
==29558== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
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