Backport from mainline

	2016-11-07  Bernd Schmidt  <bschmidt@redhat.com>

        PR rtl-optimization/77309
        * combine.c (make_compound_operation): Allow EQ for IN_CODE, and
        don't assume an equality comparison for plain COMPARE.
        (simplify_comparison): Pass a more accurate code to
        make_compound_operation.

        PR rtl-optimization/77309
        * gcc.dg/torture/pr77309.c: New test.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-6-branch@243549 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 51 insertions, 6 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d64cbfdd19a..3911e187ae3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2016-12-12  Bernd Schmidt  <bschmidt@redhat.com>
+
+	Backport from mainline
+	2016-11-07  Bernd Schmidt  <bschmidt@redhat.com>
+
+        PR rtl-optimization/77309
+        * combine.c (make_compound_operation): Allow EQ for IN_CODE, and
+        don't assume an equality comparison for plain COMPARE.
+        (simplify_comparison): Pass a more accurate code to
+        make_compound_operation.
+
 2016-12-12 Thomas Preud'homme <thomas.preudhomme@arm.com>
 
 	Backport from mainline
diff --git a/gcc/combine.c b/gcc/combine.c
index 480e8819606..75c6229766c 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -7755,7 +7755,8 @@ extract_left_shift (rtx x, int count)
 
    IN_CODE says what kind of expression we are processing.  Normally, it is
    SET.  In a memory address it is MEM.  When processing the arguments of
-   a comparison or a COMPARE against zero, it is COMPARE.  */
+   a comparison or a COMPARE against zero, it is COMPARE, or EQ if more
+   precisely it is an equality comparison against zero.  */
 
 rtx
 make_compound_operation (rtx x, enum rtx_code in_code)
@@ -7769,11 +7770,17 @@ make_compound_operation (rtx x, enum rtx_code in_code)
   rtx new_rtx = 0;
   rtx tem;
   const char *fmt;
+  bool equality_comparison = false;
 
   /* Select the code to be used in recursive calls.  Once we are inside an
      address, we stay there.  If we have a comparison, set to COMPARE,
      but once inside, go back to our default of SET.  */
 
+  if (in_code == EQ)
+    {
+      equality_comparison = true;
+      in_code = COMPARE;
+    }
   next_code = (code == MEM ? MEM
 	       : ((code == COMPARE || COMPARISON_P (x))
 		  && XEXP (x, 1) == const0_rtx) ? COMPARE
@@ -7982,11 +7989,12 @@ make_compound_operation (rtx x, enum rtx_code in_code)
       /* If we are in a comparison and this is an AND with a power of two,
 	 convert this into the appropriate bit extract.  */
       else if (in_code == COMPARE
-	       && (i = exact_log2 (UINTVAL (XEXP (x, 1)))) >= 0)
+	       && (i = exact_log2 (UINTVAL (XEXP (x, 1)))) >= 0
+	       && (equality_comparison || i < GET_MODE_PRECISION (mode) - 1))
 	new_rtx = make_extraction (mode,
-			       make_compound_operation (XEXP (x, 0),
-							next_code),
-			       i, NULL_RTX, 1, 1, 0, 1);
+				   make_compound_operation (XEXP (x, 0),
+							    next_code),
+				   i, NULL_RTX, 1, 1, 0, 1);
 
       break;
 
@@ -12391,7 +12399,11 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
      We can never remove a SUBREG for a non-equality comparison because
      the sign bit is in a different place in the underlying object.  */
 
-  op0 = make_compound_operation (op0, op1 == const0_rtx ? COMPARE : SET);
+  rtx_code op0_mco_code = SET;
+  if (op1 == const0_rtx)
+    op0_mco_code = code == NE || code == EQ ? EQ : COMPARE;
+
+  op0 = make_compound_operation (op0, op0_mco_code);
   op1 = make_compound_operation (op1, SET);
 
   if (GET_CODE (op0) == SUBREG && subreg_lowpart_p (op0)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 6b7896a59b6..0336b2486f0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2016-12-12  Bernd Schmidt  <bschmidt@redhat.com>
+
+	Backport from mainline
+	2016-11-07  Bernd Schmidt  <bschmidt@redhat.com>
+
+        PR rtl-optimization/77309
+        * gcc.dg/torture/pr77309.c: New test.
+
 2016-12-12 Thomas Preud'homme <thomas.preudhomme@arm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/gcc.dg/torture/pr77309.c b/gcc/testsuite/gcc.dg/torture/pr77309.c
new file mode 100644
index 00000000000..5bdbc0a0b83
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr77309.c
@@ -0,0 +1,14 @@
+/* { dg-do run } */
+
+int a, b;
+
+int main ()
+{
+  long c = 1 % (2 ^ b);
+  c = -c & ~(~(b ^ ~b) || a);
+
+  if (c >= 0)
+    __builtin_abort ();
+
+  return 0;
+}