https://bugs.kde.org/show_bug.cgi?id=401112
Bug ID: 401112
Summary: LLVM 5.0 generates comparison against partially
initialized data.
Product: valgrind
Version: 3.14 SVN
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: nicolas.b.pier...@nbp.name
Target Milestone: ---
Created attachment 116354
--> https://bugs.kde.org/attachment.cgi?id=116354&action=edit
Spec rule for SUBL-Cond{BE,NBE} with ((1 << N) - 1) immediate
SUMMARY
https://bugzilla.mozilla.org/show_bug.cgi?id=1489572#c47
LLVM 5.0 generates SUBL {CondBE / CondNBE} with power of 2 minus 1 immediate,
to compare the high bits of data structures, where the bottom of the data
structure might have undefined bits.
The attached patch copies the spec rule which were added previous and changes
the way N is computed, based on the ((1 << N) - 1) pattern instead. Testing on
the initial issue seems to fix the problem.
STEPS TO REPRODUCE
1. https://bugzilla.mozilla.org/show_bug.cgi?id=1489572#c47
OBSERVED RESULT
Conditional jump or move depends on uninitialised value(s)
EXPECTED RESULT
Nothing.
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