[PATCH] Fix up handling of bool BIT_NOT_EXPRs in store-merging (PR tree-optimization/84982, take 2)

[Jakub Jelinek]

On Wed, Mar 21, 2018 at 09:20:40AM +0100, Richard Biener wrote:
> > +	  tree lhs = gimple_assign_lhs (info->stmt);
> > +	  if (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE && info->bitsize > 1)
> 
> So I'm slightly uncomfortable with keying this just on BOOLEAN_TYPE.
> Do you think anything would go wrong with simply using
> 
>  if (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
>      && TYPE_PRECISION (TREE_TYPE (lhs)) < info->bitsize)
> 
> ?
> 
> It would then be any_padding rather than any_bool.

So like this?  The assembly for the testcase is still identical to previous
patch on both x86_64-linux and powerpc-linux.
I've tried to reproduce the case with non-bool integral types with precision
smaller than size, but even with C++ -fstrict-enums haven't succeeded, those
enums have different TYPE_*_VALUE, but TYPE_PRECISION is still equal to the
TYPE_SIZE, in the end I've just changed in gdb TYPE_PRECISION of the
enumerated type and checked that there is (without store merging) xor with
the mask of only precision bits emitted.  Perhaps in Ada one can construct
something?  I don't speak Ada though...

2018-03-21  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/84982
	* gimple-ssa-store-merging.c (invert_op): Handle boolean inversion
	by flipping the least significant bit rather than all bits from
	bitpos to bitpos + bitsize - 1.

	* c-c++-common/pr84982.c: New test.

--- gcc/gimple-ssa-store-merging.c.jj	2018-03-20 22:05:54.368430762 +0100
+++ gcc/gimple-ssa-store-merging.c	2018-03-21 10:45:39.919458647 +0100
@@ -3248,16 +3248,23 @@ invert_op (split_store *split_store, int
   unsigned int i;
   store_immediate_info *info;
   unsigned int cnt = 0;
+  bool any_paddings = false;
   FOR_EACH_VEC_ELT (split_store->orig_stores, i, info)
     {
       bool bit_not_p = idx < 2 ? info->ops[idx].bit_not_p : info->bit_not_p;
       if (bit_not_p)
-	++cnt;
+	{
+	  ++cnt;
+	  tree lhs = gimple_assign_lhs (info->stmt);
+	  if (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+	      && TYPE_PRECISION (TREE_TYPE (lhs)) < info->bitsize)
+	    any_paddings = true;
+	}
     }
   mask = NULL_TREE;
   if (cnt == 0)
     return NOP_EXPR;
-  if (cnt == split_store->orig_stores.length ())
+  if (cnt == split_store->orig_stores.length () && !any_paddings)
     return BIT_NOT_EXPR;
 
   unsigned HOST_WIDE_INT try_bitpos = split_store->bytepos * BITS_PER_UNIT;
@@ -3274,14 +3281,42 @@ invert_op (split_store *split_store, int
 	 clear regions with !bit_not_p, so that gaps in between stores aren't
 	 set in the mask.  */
       unsigned HOST_WIDE_INT bitsize = info->bitsize;
+      unsigned HOST_WIDE_INT prec = bitsize;
       unsigned int pos_in_buffer = 0;
+      if (any_paddings)
+	{
+	  tree lhs = gimple_assign_lhs (info->stmt);
+	  if (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+	      && TYPE_PRECISION (TREE_TYPE (lhs)) < bitsize)
+	    prec = TYPE_PRECISION (TREE_TYPE (lhs));
+	}
       if (info->bitpos < try_bitpos)
 	{
 	  gcc_assert (info->bitpos + bitsize > try_bitpos);
-	  bitsize -= (try_bitpos - info->bitpos);
+	  if (!BYTES_BIG_ENDIAN)
+	    {
+	      if (prec <= try_bitpos - info->bitpos)
+		continue;
+	      prec -= try_bitpos - info->bitpos;
+	    }
+	  bitsize -= try_bitpos - info->bitpos;
+	  if (BYTES_BIG_ENDIAN && prec > bitsize)
+	    prec = bitsize;
 	}
       else
 	pos_in_buffer = info->bitpos - try_bitpos;
+      if (prec < bitsize)
+	{
+	  /* If this is a bool inversion, invert just the least significant
+	     prec bits rather than all bits of it.  */
+	  if (BYTES_BIG_ENDIAN)
+	    {
+	      pos_in_buffer += bitsize - prec;
+	      if (pos_in_buffer >= split_store->size)
+		continue;
+	    }
+	  bitsize = prec;
+	}
       if (pos_in_buffer + bitsize > split_store->size)
 	bitsize = split_store->size - pos_in_buffer;
       unsigned char *p = buf + (pos_in_buffer / BITS_PER_UNIT);
--- gcc/testsuite/c-c++-common/pr84982.c.jj	2018-03-20 14:49:00.259744750 +0100
+++ gcc/testsuite/c-c++-common/pr84982.c	2018-03-20 12:27:34.111363552 +0100
@@ -0,0 +1,38 @@
+/* PR tree-optimization/84982 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#ifndef __cplusplus
+#define bool _Bool
+#define true 1
+#define false 0
+#endif
+
+struct S { bool a, b, c, d; };
+
+__attribute__((noipa)) void
+bar (bool *x)
+{
+  if (x[0] || !x[1] || !x[2] || x[3])
+    __builtin_abort ();
+}
+
+__attribute__((noipa)) void
+foo (struct S *x)
+{
+  bool a[4];
+  a[0] = !x->a;
+  a[1] = !x->b;
+  a[2] = x->c;
+  a[3] = !x->d;
+  bar (a);
+} 
+
+int
+main ()
+{
+  struct S s;
+  s.a = true; s.b = false; s.c = true; s.d = true;
+  foo (&s);
+  return 0;
+}


	Jakub