[PATCH] i386: Save/restore recog_data in ix86_vector_duplicate_value [PR106577]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

On Tue, Aug 16, 2022 at 09:14:06AM +0100, Richard Sandiford via Gcc-patches wrote:
> IMO the correct low-effort fix is to save and restore recog_data
> in ix86_vector_duplicate_value.  It's a relatively big copy,
> but the current code is pretty wasteful anyway (allocating at
> least a new SET and INSN for every query).  Compared to the
> overhead of doing that, a copy to and from the stack shouldn't
> be too bad.

The following patch does that.
It isn't the first spot in the compiler that does that, not even the first
spot in the i386 backend.
In i386-expand.cc beyond these 2 recog_memoized calls there is one in
expand_vselect, but I think it is unlikely we'd run into these issues trying
to expand new permutations from splitters.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2022-12-02  Jakub Jelinek  <jakub@redhat.com>

	PR target/106577
	* config/i386/i386-expand.cc (ix86_vector_duplicate_value): Save/restore
	recog_data around recog_memoized calls.

	* gcc.target/i386/pr106577.c: New test.

--- gcc/config/i386/i386-expand.cc.jj	2022-12-01 09:29:15.233466321 +0100
+++ gcc/config/i386/i386-expand.cc	2022-12-01 14:05:55.901157211 +0100
@@ -15187,6 +15187,10 @@ ix86_vector_duplicate_value (machine_mod
   bool ok;
   rtx_insn *insn;
   rtx dup;
+  /* Save/restore recog_data in case this is called from splitters
+     or other routines where recog_data needs to stay valid across
+     force_reg.  See PR106577.  */
+  recog_data_d recog_data_save = recog_data;
 
   /* First attempt to recognize VAL as-is.  */
   dup = gen_vec_duplicate (mode, val);
@@ -15212,6 +15216,7 @@ ix86_vector_duplicate_value (machine_mod
       ok = recog_memoized (insn) >= 0;
       gcc_assert (ok);
     }
+  recog_data = recog_data_save;
   return true;
 }
 
--- gcc/testsuite/gcc.target/i386/pr106577.c.jj	2022-12-01 14:13:03.973872383 +0100
+++ gcc/testsuite/gcc.target/i386/pr106577.c	2022-12-01 14:13:03.973872383 +0100
@@ -0,0 +1,10 @@
+/* PR target/106577 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -mavx" } */
+
+int i;
+void
+foo (void)
+{
+  i ^= !(((unsigned __int128)0xf0f0f0f0f0f0f0f0 << 64 | 0xf0f0f0f0f0f0f0f0) & i);
+}


	Jakub