[committed] Another 6.x backport (PR testsuite/80678)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

Apparently one of the testcases in my recent 6.x backports
ICEs on powerpc64le-linux and doesn't on the trunk/7.x.

The following backports fix that, bootstrapped/regtested
on x86_64-linux and i686-linux and additionally tested with
a cross-compiler on the constexpr-77* and pr71310.c testcases,
committed to 6.x branch.

2017-05-09  Jakub Jelinek  <jakub@redhat.com>

	PR testsuite/80678
	2016-06-14  Richard Biener  <rguenther@suse.de>

	PR middle-end/71310
	PR bootstrap/71510
	* expr.h (get_bit_range): Declare.
	* expr.c (get_bit_range): Export.
	* fold-const.c (optimize_bit_field_compare): Use get_bit_range and
	word_mode again to constrain the bitfield access.

	2016-06-11  Segher Boessenkool  <segher@kernel.crashing.org>

	PR middle-end/71310
	* fold-const.c (optimize_bit_field_compare): Don't try to use
	word_mode unconditionally for reading the bit field, look at
	DECL_BIT_FIELD_REPRESENTATIVE instead.

	* gcc.target/powerpc/pr71310.c: New testcase.

--- gcc/fold-const.c	(revision 237318)
+++ gcc/fold-const.c	(revision 237426)
@@ -3902,9 +3902,19 @@
        return 0;
    }
 
+  /* Honor the C++ memory model and mimic what RTL expansion does.  */
+  unsigned HOST_WIDE_INT bitstart = 0;
+  unsigned HOST_WIDE_INT bitend = 0;
+  if (TREE_CODE (lhs) == COMPONENT_REF)
+    {
+      get_bit_range (&bitstart, &bitend, lhs, &lbitpos, &offset);
+      if (offset != NULL_TREE)
+	return 0;
+    }
+
   /* See if we can find a mode to refer to this field.  We should be able to,
      but fail if we can't.  */
-  nmode = get_best_mode (lbitsize, lbitpos, 0, 0,
+  nmode = get_best_mode (lbitsize, lbitpos, bitstart, bitend,
 			 const_p ? TYPE_ALIGN (TREE_TYPE (linner))
 			 : MIN (TYPE_ALIGN (TREE_TYPE (linner)),
 				TYPE_ALIGN (TREE_TYPE (rinner))),
--- gcc/expr.c	(revision 237425)
+++ gcc/expr.c	(revision 237426)
@@ -4795,7 +4795,7 @@ optimize_bitfield_assignment_op (unsigne
    If the access does not need to be restricted, 0 is returned in both
    *BITSTART and *BITEND.  */
 
-static void
+void
 get_bit_range (unsigned HOST_WIDE_INT *bitstart,
 	       unsigned HOST_WIDE_INT *bitend,
 	       tree exp,
--- gcc/expr.h	(revision 237425)
+++ gcc/expr.h	(revision 237426)
@@ -242,6 +242,10 @@ extern rtx push_block (rtx, int, int);
 extern bool emit_push_insn (rtx, machine_mode, tree, rtx, unsigned int,
 			    int, rtx, int, rtx, rtx, int, rtx, bool);
 
+/* Extract the accessible bit-range from a COMPONENT_REF.  */
+extern void get_bit_range (unsigned HOST_WIDE_INT *, unsigned HOST_WIDE_INT *,
+			   tree, HOST_WIDE_INT *, tree *);
+
 /* Expand an assignment that stores the value of FROM into TO.  */
 extern void expand_assignment (tree, tree, bool);
 
--- gcc/testsuite/gcc.target/powerpc/pr71310.c	(nonexistent)
+++ gcc/testsuite/gcc.target/powerpc/pr71310.c	(revision 237319)
@@ -0,0 +1,23 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-options "-O2" } */
+
+/* { dg-final { scan-assembler-not {\mld} } } */
+/* { dg-final { scan-assembler-not {\mlwz} } } */
+/* { dg-final { scan-assembler-times {\mlbz} 2 } } */
+
+struct mmu_gather {
+        long end;
+        int fullmm : 1;
+};
+
+void __tlb_reset_range(struct mmu_gather *p1)
+{
+        if (p1->fullmm)
+                p1->end = 0;
+}
+
+void tlb_gather_mmu(struct mmu_gather *p1)
+{
+        p1->fullmm = 1;
+        __tlb_reset_range(p1);
+}

	Jakub