tree eec207ac9f94152abb8519ebb3c71a2d578eab9f
parent b539787af7c99b0c60c02ef802c930138c3e4fb4
author Hans Wennborg <hans@hanshq.net> 1516206824 +0000
committer Hans Wennborg <hans@hanshq.net> 1516206824 +0000

Merging r321751, r321806, and r321878:

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r321751 | arsenm | 2018-01-03 10:45:37 -0800 (Wed, 03 Jan 2018) | 25 lines

StructurizeCFG: Fix broken backedge detection

The work order was changed in r228186 from SCC order
to RPO with an arbitrary sorting function. The sorting
function attempted to move inner loop nodes earlier. This
was was apparently relying on an assumption that every block
in a given loop / the same loop depth would be seen before
visiting another loop. In the broken testcase, a block
outside of the loop was encountered before moving onto
another block in the same loop. The testcase would then
structurize such that one blocks unconditional successor
could never be reached.

Revert to plain RPO for the analysis phase. This fixes
detecting edges as backedges that aren't really.

The processing phase does use another visited set, and
I'm unclear on whether the order there is as important.
An arbitrary order doesn't work, and triggers some infinite
loops. The reversed RPO list seems to work and is closer
to the order that was used before, minus the arbitary
custom sorting.

A few of the changed tests now produce smaller code,
and a few are slightly worse looking.
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r321806 | arsenm | 2018-01-04 09:23:24 -0800 (Thu, 04 Jan 2018) | 4 lines

StructurizeCFG: xfail one of the testcases from r321751

It fails with -verify-region-info. This seems to be a issue
with RegionInfo itself which existed before.
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r321878 | arsenm | 2018-01-05 09:51:36 -0800 (Fri, 05 Jan 2018) | 4 lines

RegionInfo: Use report_fatal_error instead of llvm_unreachable

Otherwise when using -verify-region-info in a release build the
error won't be emitted.
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llvm-svn: 322686