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To: gcc-patches@gcc.gnu.org
Subject: PR 71020: Handle abnormal PHIs in tree-call-cdce.c
From: Richard Sandiford <richard.sandiford@arm.com>
Gcc: private.sent
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The PR is about a case where tree-call-cdce.c causes two abnormal
PHIs for the same variable to be live at the same time, leading to
a coalescing failure.  It seemed like getting rid of these kinds of
input would be generally useful, so I added a utility to tree-dfa.c.

Tested on x86_64-linux-gnu.

gcc/
	PR middle-end/71020
	* tree-dfa.h (replace_abnormal_ssa_names): Declare.
	* tree-dfa.c (replace_abnormal_ssa_names): New function.
	* tree-call-cdce.c: Include tree-dfa.h.
	(can_guard_call_p): New function, extracted from...
	(can_use_internal_fn): ...here.
	(shrink_wrap_one_built_in_call_with_conds): Remove failure path
	and return void.
	(shrink_wrap_one_built_in_call): Likewise.
	(use_internal_fn): Likewise.
	(shrink_wrap_conditional_dead_built_in_calls): Update accordingly
	and return void.  Call replace_abnormal_ssa_names.
	(pass_call_cdce::execute): Check can_guard_call_p during the
	initial walk.  Assume shrink_wrap_conditional_dead_built_in_calls
	will always change something.

gcc/testsuite/
	* gcc.dg/torture/pr71020.c: New test.

From-SVN: r236393