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

[Jakub Jelinek]

Hi!

Boolean !x is often expanded as ^ 1, but store merging it actually merges
as ^ 255 (for 8-bit bool), which is incorrect.

The following patch fixes it to do that ^ 1 instead.

Bootstrapped/regtested on x86_64-linux and i686-linux and checked on the
testcase with -> powerpc64-linux cross, ok for trunk?

2018-03-20  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 13:53:31.701938584 +0100
+++ gcc/gimple-ssa-store-merging.c	2018-03-20 14:39:50.925657339 +0100
@@ -3248,16 +3248,22 @@ invert_op (split_store *split_store, int
   unsigned int i;
   store_immediate_info *info;
   unsigned int cnt = 0;
+  bool any_bools = 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 (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE && info->bitsize > 1)
+	    any_bools = 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_bools)
     return BIT_NOT_EXPR;
 
   unsigned HOST_WIDE_INT try_bitpos = split_store->bytepos * BITS_PER_UNIT;
@@ -3275,13 +3281,34 @@ invert_op (split_store *split_store, int
 	 set in the mask.  */
       unsigned HOST_WIDE_INT bitsize = info->bitsize;
       unsigned int pos_in_buffer = 0;
+      bool is_bool = false;
+      if (any_bools && bitsize > 1)
+	{
+	  tree lhs = gimple_assign_lhs (info->stmt);
+	  if (TREE_CODE (TREE_TYPE (lhs)) == BOOLEAN_TYPE)
+	    is_bool = true;
+	}
       if (info->bitpos < try_bitpos)
 	{
 	  gcc_assert (info->bitpos + bitsize > try_bitpos);
 	  bitsize -= (try_bitpos - info->bitpos);
+	  if (is_bool && !BYTES_BIG_ENDIAN)
+	    continue;
 	}
       else
 	pos_in_buffer = info->bitpos - try_bitpos;
+      if (is_bool && bitsize)
+	{
+	  /* If this is a bool inversion, invert just the LSB
+	     rather than all bits of it.  */
+	  if (BYTES_BIG_ENDIAN)
+	    {
+	      pos_in_buffer += bitsize - 1;
+	      if (pos_in_buffer >= split_store->size)
+		continue;
+	    }
+	  bitsize = 1;
+	}
       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