[PATCH] tree-optimization/103345: Improved load merging

[Roger Sayle]

This patch implements PR tree-optimization/103345 to merge adjacent
loads when combined with addition or bitwise xor.  The current code
in gimple-ssa-store-merging.c's find_bswap_or_nop alreay handles ior,
so that all that's required is to treat PLUS_EXPR and BIT_XOR_EXPR in
the same way at BIT_IOR_EXPR.  Many thanks to Andrew Pinski for
pointing out that this also resolves PR target/98953.

This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check with no new failures.  The new testcases should also
pass (but haven't been tested) on other endian targets.

Ok for mainline?


2021-11-22  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR tree-optimization/98953
	PR tree-optimization/103345
	* gimple-ssa-store-merging.c (find_bswap_or_nop_1): Handle
	BIT_XOR_EXPR and PLUS_EXPR the same as BIT_IOR_EXPR.
	(pass_optimize_bswap::execute): Likewise.

gcc/testsuite/ChangeLog
	PR tree-optimization/98953
	PR tree-optimization/103345
	* gcc.dg/tree-ssa/pr98953.c: New test case.
	* gcc.dg/tree-ssa/pr103345.c: New test case.


Thanks in advance,
Roger
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