re PR c/83844 (ICE with warn_if_not_aligned attribute)

	PR c/83844
	* stor-layout.c (handle_warn_if_not_align): Use byte_position and
	multiple_of_p instead of unchecked tree_to_uhwi and UHWI check.
	If off is not INTEGER_CST, issue a may not be aligned warning
	rather than isn't aligned.  Use isn%'t rather than isn't.
	* fold-const.c (multiple_of_p) <case BIT_AND_EXPR>: Don't fall through
	into MULT_EXPR.
	<case MULT_EXPR>: Improve the case when bottom and one of the
	MULT_EXPR operands are INTEGER_CSTs and bottom is multiple of that
	operand, in that case check if the other operand is multiple of
	bottom divided by the INTEGER_CST operand.

	* gcc.dg/pr83844.c: New test.

From-SVN: r256745

5 files changed, 91 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index abe3295..9b7bf83 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,17 @@
+2018-01-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/83844
+	* stor-layout.c (handle_warn_if_not_align): Use byte_position and
+	multiple_of_p instead of unchecked tree_to_uhwi and UHWI check.
+	If off is not INTEGER_CST, issue a may not be aligned warning
+	rather than isn't aligned.  Use isn%'t rather than isn't.
+	* fold-const.c (multiple_of_p) <case BIT_AND_EXPR>: Don't fall through
+	into MULT_EXPR.
+	<case MULT_EXPR>: Improve the case when bottom and one of the
+	MULT_EXPR operands are INTEGER_CSTs and bottom is multiple of that
+	operand, in that case check if the other operand is multiple of
+	bottom divided by the INTEGER_CST operand.
+
 2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR target/83858
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 5cf2052..1ea3766 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -12595,9 +12595,34 @@ multiple_of_p (tree type, const_tree top, const_tree bottom)
 	 a multiple of BOTTOM then TOP is a multiple of BOTTOM.  */
       if (!integer_pow2p (bottom))
 	return 0;
-      /* FALLTHRU */
+      return (multiple_of_p (type, TREE_OPERAND (top, 1), bottom)
+	      || multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
 
     case MULT_EXPR:
+      if (TREE_CODE (bottom) == INTEGER_CST)
+	{
+	  op1 = TREE_OPERAND (top, 0);
+	  op2 = TREE_OPERAND (top, 1);
+	  if (TREE_CODE (op1) == INTEGER_CST)
+	    std::swap (op1, op2);
+	  if (TREE_CODE (op2) == INTEGER_CST)
+	    {
+	      if (multiple_of_p (type, op2, bottom))
+		return 1;
+	      /* Handle multiple_of_p ((x * 2 + 2) * 4, 8).  */
+	      if (multiple_of_p (type, bottom, op2))
+		{
+		  widest_int w = wi::sdiv_trunc (wi::to_widest (bottom),
+						 wi::to_widest (op2));
+		  if (wi::fits_to_tree_p (w, TREE_TYPE (bottom)))
+		    {
+		      op2 = wide_int_to_tree (TREE_TYPE (bottom), w);
+		      return multiple_of_p (type, op1, op2);
+		    }
+		}
+	      return multiple_of_p (type, op1, bottom);
+	    }
+	}
       return (multiple_of_p (type, TREE_OPERAND (top, 1), bottom)
 	      || multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
 
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 0f65e16..8c415ebb 100644
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -1150,12 +1150,16 @@ handle_warn_if_not_align (tree field, unsigned int record_align)
     warning (opt_w, "alignment %u of %qT is less than %u",
 	     record_align, context, warn_if_not_align);
 
-  unsigned HOST_WIDE_INT off
-    = (tree_to_uhwi (DECL_FIELD_OFFSET (field))
-       + tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)) / BITS_PER_UNIT);
-  if ((off % warn_if_not_align) != 0)
-    warning (opt_w, "%q+D offset %wu in %qT isn't aligned to %u",
-	     field, off, context, warn_if_not_align);
+  tree off = byte_position (field);
+  if (!multiple_of_p (TREE_TYPE (off), off, size_int (warn_if_not_align)))
+    {
+      if (TREE_CODE (off) == INTEGER_CST)
+	warning (opt_w, "%q+D offset %E in %qT isn%'t aligned to %u",
+		 field, off, context, warn_if_not_align);
+      else
+	warning (opt_w, "%q+D offset %E in %qT may not be aligned to %u",
+		 field, off, context, warn_if_not_align);
+    }
 }
 
 /* Called from place_field to handle unions.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9bc4d7b..ec9f469 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-01-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/83844
+	* gcc.dg/pr83844.c: New test.
+
 2018-01-16  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	* gcc.dg/torture/pr83847.c: New test.
diff --git a/gcc/testsuite/gcc.dg/pr83844.c b/gcc/testsuite/gcc.dg/pr83844.c
new file mode 100644
index 0000000..c6db68a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr83844.c
@@ -0,0 +1,36 @@
+/* PR c/83844 */
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wall" } */
+
+typedef unsigned long long __u64 __attribute__((aligned(4),warn_if_not_aligned(8)));
+void bar (void *, void *, void *);
+
+void
+foo (int n)
+{
+  struct A
+  {
+    int i1;
+    int i2;
+    int i3[n];
+    __u64 x;	/* { dg-warning "in 'struct A' may not be aligned to 8" } */
+  } __attribute__((aligned (8)));
+  struct B
+  {
+    int i1;
+    int i2;
+    long long i3[n];
+    __u64 x;
+  } __attribute__((aligned (8)));
+  struct C
+  {
+    int i1;
+    int i2;
+    int i3[2 * n];
+    __u64 x;
+  } __attribute__((aligned (8)));
+  struct A a;
+  struct B b;
+  struct C c;
+  bar (&a, &b, &c);
+}