commit 329475795c6eeaa2b122672091c9119b9d6c5564
author Jakub Jelinek <jakub@redhat.com> Thu Jan 30 21:28:17 2020 +0100
committer Jakub Jelinek <jakub@redhat.com> Thu Feb 13 21:32:23 2020 +0100
tree 879fbeaaa3b9d287f0483167c2fae6d19a648fa3
parent 4b124e3c9c35121969cc23d0aea4bcb2c406fd21

combine: Punt on out of range rotate counts [PR93505]

What happens on this testcase is with the out of bounds rotate we get:
Trying 13 -> 16:
   13: r129:SI=r132:DI#0<-<0x20
      REG_DEAD r132:DI
   16: r123:DI=r129:SI<0
      REG_DEAD r129:SI
Successfully matched this instruction:
(set (reg/v:DI 123 [ <retval> ])
    (const_int 0 [0]))
during combine.  So, perhaps we could also change simplify-rtx.c to punt
if it is out of bounds rather than trying to optimize anything.
Or, but probably GCC11 material, if we decide that ROTATE/ROTATERT doesn't
have out of bounds counts or introduce targetm.rotate_truncation_mask,
we should truncate the argument instead of punting.
Punting is better for backports though.

2020-01-30  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/93505
	* combine.c (simplify_comparison) <case ROTATE>: Punt on out of range
	rotate counts.

	* gcc.c-torture/compile/pr93505.c: New test.