aarch64: Fix ICE due to aarch64_gen_compare_reg_maybe_ze [PR94435]

aarch64: Fix ICE due to aarch64_gen_compare_reg_maybe_ze [PR94435]

The following testcase ICEs, because aarch64_gen_compare_reg_maybe_ze emits
invalid RTL.
For y_mode [QH]Imode it expects y to be of that mode (or CONST_INT that fits
into that mode) and x being SImode; for non-CONST_INT y it zero extends y
into SImode and compares that against x, for CONST_INT y it zero extends y
into SImode.  The problem is that when the zero extended constant isn't
usable directly, it forces it into a REG, but with y_mode mode, and then
compares against y.  That is wrong, because it should force it into a SImode
REG and compare that way.

2020-04-02  Jakub Jelinek  <jakub@redhat.com>

	PR target/94435
	* config/aarch64/aarch64.c (aarch64_gen_compare_reg_maybe_ze): For
	y_mode E_[QH]Imode and y being a CONST_INT, change y_mode to SImode.

	* gcc.target/aarch64/pr94435.c: New test.