[llvm-bugs] [Bug 37970] New: clang non-deterministic DEBUG_VALUE output, armv7a-linux-androideabi -mthumb -O2 -g
llvm-bugs at lists.llvm.org
Wed Jun 27 13:42:38 PDT 2018
Bug ID: 37970
Summary: clang non-deterministic DEBUG_VALUE output,
armv7a-linux-androideabi -mthumb -O2 -g
Component: Backend: ARM
Assignee: unassignedbugs at nondot.org
Reporter: chh at google.com
CC: llvm-bugs at lists.llvm.org
Created attachment 20485
output 1.s and 2.s have different @DEBUG_VALUE sequences
To reproduce, modify and run the run.sh script in the test.zip.
Repeated compilations of the same input file produced different @DEBUG_VALUE
sequences in 1.s and 2.s.
The problem occurred with -target armv7a-linux-androideabi -mthumb -O2 -g.
Other targets, -O1, or -g1 seemed to produce deterministic output.
I traced back to llvm change https://reviews.llvm.org/rL321862,
which started to have such problem. I am not sure if that change
is buggy or just exposed an older bug.
The test case was reduced from Android open source code.
It is required in Android release process to be able to generate identical
output from the same input and compiler. We cannot release Android without a
fix or reversing rL321862.
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