[PATCH] bitint, v2: Avoid rewriting large/huge _BitInt vars into SSA after bitint lowering [PR114278]

[Jakub Jelinek <jakub@redhat.com>]

On Sat, Mar 09, 2024 at 12:25:42PM +0100, Richard Biener wrote:
> Ideally we’d clear TREE_ADDRESSABLE but set DECL_NOT_GIMPLE_REG,
> I think the analysis where we check the base would be a more
> appropriate place to enforce that.

So like this?

Bootstrapped/regtested on x86_64-linux and i686-linux.

2024-03-11  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/114278
	* tree-ssa.cc (maybe_optimize_var): If large/huge _BitInt vars are no
	longer addressable, set DECL_NOT_GIMPLE_REG_P on them.

	* gcc.dg/bitint-99.c: New test.

--- gcc/tree-ssa.cc.jj	2024-01-03 11:51:39.902615009 +0100
+++ gcc/tree-ssa.cc	2024-03-09 23:34:12.469223987 +0100
@@ -1785,6 +1785,20 @@ maybe_optimize_var (tree var, bitmap add
 	      fprintf (dump_file, "\n");
 	    }
 	}
+      else if (TREE_CODE (TREE_TYPE (var)) == BITINT_TYPE
+	       && (cfun->curr_properties & PROP_gimple_lbitint) != 0
+	       && TYPE_PRECISION (TREE_TYPE (var)) > MAX_FIXED_MODE_SIZE)
+	{
+	  /* Don't rewrite large/huge _BitInt vars after _BitInt lowering
+	     into SSA form.  */
+	  DECL_NOT_GIMPLE_REG_P (var) = 1;
+	  if (dump_file)
+	    {
+	      fprintf (dump_file, "_BitInt var after its lowering: ");
+	      print_generic_expr (dump_file, var);
+	      fprintf (dump_file, "\n");
+	    }
+	}
       else if (DECL_NOT_GIMPLE_REG_P (var))
 	{
 	  maybe_reg = true;
--- gcc/testsuite/gcc.dg/bitint-99.c.jj	2024-03-08 14:26:17.658069942 +0100
+++ gcc/testsuite/gcc.dg/bitint-99.c	2024-03-08 14:25:36.292645965 +0100
@@ -0,0 +1,26 @@
+/* PR tree-optimization/114278 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-O2 -fno-tree-dce -fno-tree-dse -fno-tree-ccp" } */
+/* { dg-additional-options "-mavx2" { target i?86-*-* x86_64-*-* } } */
+
+void
+foo (void *p)
+{
+  _BitInt(64) b = *(_BitInt(64) *) __builtin_memmove (&b, p, sizeof (_BitInt(64)));
+}
+
+#if __BITINT_MAXWIDTH__ >= 128
+void
+bar (void *p)
+{
+  _BitInt(128) b = *(_BitInt(128) *) __builtin_memmove (&b, p, sizeof (_BitInt(128)));
+}
+#endif
+
+#if __BITINT_MAXWIDTH__ >= 256
+void
+baz (void *p)
+{
+  _BitInt(256) b = *(_BitInt(256) *) __builtin_memmove (&b, p, sizeof (_BitInt(256)));
+}
+#endif

	Jakub