[Bug tree-optimization/93435] [8/9/10 Regression] Hang with -O2 on innocuous looking code with GCC 8.3

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93435

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Jambor <jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:29f23ed79b60949fc60f6fdbbd931bd58090b241

commit r10-7309-g29f23ed79b60949fc60f6fdbbd931bd58090b241
Author: Martin Jambor <mjambor@suse.cz>
Date:   Sat Mar 21 00:21:02 2020 +0100

    sra: Cap number of sub-access propagations with a param (PR 93435)

    PR 93435 is a perfect SRA bomb.  It initializes an array of 16 chars
    element-wise, then uses that to initialize an aggregate that consists
    of four such arrays, that one to initialize one four times as big as
    the previous one all the way to an aggregate that has 64kb.

    This causes the sub-access propagation across assignments to create
    thousands of byte-sized artificial accesses which are then eligible to
    be replaced - they do facilitate forward propagation but there is
    enough of them for DSE to never finish.

    This patch avoids that situation by accounting how many of such
    replacements can be created per SRA candidate.  The default value of
    32 was just the largest power of two that did not slow down
    compilation of the testcase, but it should also hopefully be big
    enough for any reasonable input that might rely on the optimization.

    2020-03-20  Martin Jambor  <mjambor@suse.cz>

            PR tree-optimization/93435
            * params.opt (sra-max-propagations): New parameter.
            * tree-sra.c (propagation_budget): New variable.
            (budget_for_propagation_access): New function.
            (propagate_subaccesses_from_rhs): Use it.
            (propagate_subaccesses_from_lhs): Likewise.
            (propagate_all_subaccesses): Set up and destroy propagation_budget.

            gcc/testsuite/
            * gcc.dg/tree-ssa/pr93435.c: New test.