[gcc r11-6232] Fix trap in pointer conversion in op1_range.

[gcc r11-6232] Fix trap in pointer conversion in op1_range.

[Andrew Macleod]

https://gcc.gnu.org/g:c25b504636fec7bf8f181a84af83a52757ba7e89

commit r11-6232-gc25b504636fec7bf8f181a84af83a52757ba7e89
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Thu Dec 17 09:24:11 2020 -0500

    Fix trap in pointer conversion in op1_range.
    
    Processing op1_range for conversion between a non-pointer and pointer
    shouldnt do any fancy math.
    
            gcc/
            PR tree-optimization/97750
            * range-op.cc (operator_cast::op1_range): Handle pointers better.
            gcc/testsuite/
            * gcc.dg/pr97750.c: New.

Diff:
---
 gcc/range-op.cc                | 25 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/pr97750.c | 21 +++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 36f9fd66cb3..a473f33169d 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1850,6 +1850,31 @@ operator_cast::op1_range (irange &r, tree type,
   tree lhs_type = lhs.type ();
   gcc_checking_assert (types_compatible_p (op2.type(), type));
 
+  // If we are calculating a pointer, shortcut to what we really care about.
+  if (POINTER_TYPE_P (type))
+    {
+      // Conversion from other pointers or a constant (including 0/NULL)
+      // are straightforward.
+      if (POINTER_TYPE_P (lhs.type ())
+	  || (lhs.singleton_p ()
+	      && TYPE_PRECISION (lhs.type ()) >= TYPE_PRECISION (type)))
+	{
+	  r = lhs;
+	  range_cast (r, type);
+	}
+      else
+	{
+	  // If the LHS is not a pointer nor a singleton, then it is
+	  // either VARYING or non-zero.
+	  if (!lhs.contains_p (build_zero_cst (lhs.type ())))
+	    r.set_nonzero (type);
+	  else
+	    r.set_varying (type);
+	}
+      r.intersect (op2);
+      return true;
+    }
+
   if (truncating_cast_p (op2, lhs))
     {
       if (lhs.varying_p ())
diff --git a/gcc/testsuite/gcc.dg/pr97750.c b/gcc/testsuite/gcc.dg/pr97750.c
new file mode 100644
index 00000000000..822b53abcff
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97750.c
@@ -0,0 +1,21 @@
+/* PR tree-optimization/97750 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wall -Wextra" } */
+
+char CopyPlane_src;
+long CopyPlane_copy_pitch;
+char *CopyFromUswc_src;
+int CopyFromUswc_height;
+void CopyPlane(char *dst) {
+  __builtin_memcpy(dst, &CopyPlane_src, CopyPlane_copy_pitch);
+}
+void CopyFromUswc(long src_pitch) {
+  char *dst;
+  for (; CopyFromUswc_height;) {
+    unsigned unaligned = (long)CopyFromUswc_src;
+    if (unaligned)
+      CopyPlane(&dst[unaligned]);  /* { dg-warning "may be used uninitialized" } */
+    CopyFromUswc_src += src_pitch;
+  }
+}
+