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Shortcut identity VEC_PERM expansion [PR94710]

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This PR is about the rs6000 backend emitting wrong assembly
for whole vector shift by 0, and while I think it is desirable
to fix the backend, I don't see a point why the expander should
try to emit that, whole vector shift by 0 is identity, we can just
return the operand.

2020-04-23  Jakub Jelinek  <jakub@redhat.com>

	PR target/94710
	* optabs.c (expand_vec_perm_const): For shift_amt const0_rtx
	just return v2.
This commit is contained in:
Jakub Jelinek 2020-04-23 21:57:50 +02:00
parent 3dbc772128
commit f51be2fb86
2 changed files with 6 additions and 0 deletions
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gcc/ChangeLog
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@ -1,5 +1,9 @@
2020-04-23 Jakub Jelinek <jakub@redhat.com>
PR target/94710
* optabs.c (expand_vec_perm_const): For shift_amt const0_rtx
just return v2.
PR middle-end/94724
* tree.c (get_narrower): Instead of creating COMPOUND_EXPRs
temporarily with non-final second operand and updating it later,

2
gcc/optabs.c
View file

@ -5627,6 +5627,8 @@ expand_vec_perm_const (machine_mode mode, rtx v0, rtx v1,
if (shift_amt)
{
class expand_operand ops[3];
if (shift_amt == const0_rtx)
return v2;
if (shift_code != CODE_FOR_nothing)
{
create_output_operand (&ops[0], target, mode);