Possible bug in LLC at -O1

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#1

Hi

I am seeing an issue (compiled application seg faults) when llc is
used at -O1. I first need to triage out which optimization/pass is
responsible for the seg fault. As such I am following this strategy:
disable gradually those passes at -O1 which do not exist at -O0. For
this I used -pass-debug=Structure. [ diff pasted at the end for
reference]

The problem is I have used almost all -disable-* options from llc
hidden help. Yet I could not make it equivalent to -O0. Here are my
questions:

1. For some reason, I am not able to use -regalloc=fast at -O1. Gives
the following error:

   $ llc -regalloc=fast -O1 -mcpu=bdver2 test.ll
    LLVM ERROR: regalloc=... not currently supported with -O0

  How do I switch to "fast" allocator at -O1?

2. How do I disable following passes:
      (a) Optimize for code generation
      (b) Remove dead machine instructions
      (c) Optimize machine instruction PHIs
      (d) Remove unreachable machine basic blocks

(Note that I am already using -disable-machine-dse, cse, -machine-sink
, lsr ...)

3. Is there any other better way to see which pass(es) are responsible
for the seg fault at -O1 ?

#2

Hi

I am seeing an issue (compiled application seg faults) when llc is
used at -O1. I first need to triage out which optimization/pass is
responsible for the seg fault. As such I am following this strategy:
disable gradually those passes at -O1 which do not exist at -O0. For
this I used -pass-debug=Structure. [ diff pasted at the end for
reference]

The problem is I have used almost all -disable-* options from llc
hidden help. Yet I could not make it equivalent to -O0. Here are my
questions:

1. For some reason, I am not able to use -regalloc=fast at -O1. Gives
the following error:

   $ llc -regalloc=fast -O1 -mcpu=bdver2 test.ll
    LLVM ERROR: regalloc=... not currently supported with -O0

  How do I switch to "fast" allocator at -O1?

<ping>

Not much help on register allocator issue either?

#3

For what its worth, many people in the US are out on vacation this week.

-Chris

#4

llc -optimize-regalloc=0

/jakob

#5

Thanks! In one of those trial and error methods, I was using both
optimize-regalloc=0
-regalloc=fast. Need to drop -regalloc then.