[PATCH] tree-optimization/110243 - IVOPTs introducing undefined overflow

[Richard Biener]

The following addresses IVOPTs rewriting expressions in its
strip_offset without caring for definedness of overflow.  Rather
than the earlier attempt of just using the proper
split_constant_offset from data-ref analysis the following adjusts
IVOPTs helper trying to minimize changes from this fix, possibly
easing backports.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

        PR tree-optimization/110243
        PR tree-optimization/111336
        * tree-ssa-loop-ivopts.cc (strip_offset_1): Rewrite
        operations with undefined behavior on overflow to
        unsigned arithmetic.

        * gcc.dg/torture/pr110243.c: New testcase.
        * gcc.dg/torture/pr111336.c: Likewise.
---
 gcc/testsuite/gcc.dg/torture/pr110243.c | 22 ++++++++++++++++++
 gcc/testsuite/gcc.dg/torture/pr111336.c | 25 ++++++++++++++++++++
 gcc/tree-ssa-loop-ivopts.cc             | 31 ++++++++++++++++++++++---
 3 files changed, 75 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr110243.c
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr111336.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr110243.c 
b/gcc/testsuite/gcc.dg/torture/pr110243.c
new file mode 100644
index 00000000000..07dffd95d4d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr110243.c
@@ -0,0 +1,22 @@
+/* { dg-do run } */
+/* { dg-require-effective-target lp64 } */
+
+#define X 1100000000
+unsigned char a;
+long b = X;
+int c[9][1];
+unsigned d;
+static long *e = &b, *f = &b;
+int g() {
+  if (a && a <= '9')
+    return '0';
+  if (a)
+    return 10;
+  return -1;
+}
+int main() {
+  d = 0;
+  for (; (int)*f -(X-1) + d < 9; d++)
+    c[g() + (int)*f + ((int)*e - X) -(X-1) + d]
+     [0] = 0;
+}
diff --git a/gcc/testsuite/gcc.dg/torture/pr111336.c 
b/gcc/testsuite/gcc.dg/torture/pr111336.c
new file mode 100644
index 00000000000..a2fa12258df
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr111336.c
@@ -0,0 +1,25 @@
+/* { dg-do run } */
+/* { dg-require-effective-target lp64 } */
+
+extern void abort (void);
+int a, b;
+long c = 3521733542;
+int d[2];
+int e(int f, int g) {
+  if (f == 0)
+    return 0;
+  if (f > 200)
+    return 0;
+  if (g)
+    return 5 * f;
+  return 0;
+}
+int main()
+{
+  int h = 0;
+  for (; e((int)c + 773233762, c + 60) + 773163185 + h < 2; h++)
+    d[h] = b;
+  if (a != 0)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 2c1f0846c88..98e5b3024db 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -2829,12 +2829,29 @@ strip_offset_1 (tree expr, bool inside_addr, bool 
top_compref,
       else if (integer_zerop (op0))
        {
          if (code == MINUS_EXPR)
-           expr = fold_build1 (NEGATE_EXPR, type, op1);
+           {
+             if (TYPE_OVERFLOW_UNDEFINED (type))
+               {
+                 type = unsigned_type_for (type);
+                 op1 = fold_convert (type, op1);
+               }
+             expr = fold_build1 (NEGATE_EXPR, type, op1);
+           }
          else
            expr = op1;
        }
       else
-       expr = fold_build2 (code, type, op0, op1);
+       {
+         if (TYPE_OVERFLOW_UNDEFINED (type))
+           {
+             type = unsigned_type_for (type);
+             if (code == POINTER_PLUS_EXPR)
+               code = PLUS_EXPR;
+             op0 = fold_convert (type, op0);
+             op1 = fold_convert (type, op1);
+           }
+         expr = fold_build2 (code, type, op0, op1);
+       }
 
       return fold_convert (orig_type, expr);
 
@@ -2852,7 +2869,15 @@ strip_offset_1 (tree expr, bool inside_addr, bool 
top_compref,
       if (integer_zerop (op0))
        expr = op0;
       else
-       expr = fold_build2 (MULT_EXPR, type, op0, op1);
+       {
+         if (TYPE_OVERFLOW_UNDEFINED (type))
+           {
+             type = unsigned_type_for (type);
+             op0 = fold_convert (type, op0);
+             op1 = fold_convert (type, op1);
+           }
+         expr = fold_build2 (MULT_EXPR, type, op0, op1);
+       }
 
       return fold_convert (orig_type, expr);
 
-- 
2.35.3