[PATCH] middle-end/94206 fix memset folding to avoid types with padding

[Richard Biener]

This makes sure that the store a memset is folded to uses a type
covering all bits.

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

Richard.

2020-03-18   Richard Biener  <rguent...@suse.de>

        PR middle-end/94206
        * gimple-fold.c (gimple_fold_builtin_memset): Avoid using
        partial int modes or not mode-precision integer types for
        the store.

        * gcc.dg/torture/pr94206.c: New testcase.
---
 gcc/gimple-fold.c                      |  6 ++++++
 gcc/testsuite/gcc.dg/torture/pr94206.c | 17 +++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr94206.c

diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 3f17de974ed..c5939f19f59 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -1235,12 +1235,18 @@ gimple_fold_builtin_memset (gimple_stmt_iterator *gsi, 
tree c, tree len)
 
   length = tree_to_uhwi (len);
   if (GET_MODE_SIZE (SCALAR_INT_TYPE_MODE (etype)) != length
+      || (GET_MODE_PRECISION (SCALAR_INT_TYPE_MODE (etype))
+         != GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE (etype)))
       || get_pointer_alignment (dest) / BITS_PER_UNIT < length)
     return NULL_TREE;
 
   if (length > HOST_BITS_PER_WIDE_INT / BITS_PER_UNIT)
     return NULL_TREE;
 
+  if (!type_has_mode_precision_p (etype))
+    etype = lang_hooks.types.type_for_mode (SCALAR_INT_TYPE_MODE (etype),
+                                           TYPE_UNSIGNED (etype));
+
   if (integer_zerop (c))
     cval = 0;
   else
diff --git a/gcc/testsuite/gcc.dg/torture/pr94206.c 
b/gcc/testsuite/gcc.dg/torture/pr94206.c
new file mode 100644
index 00000000000..9e54bba4ed4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr94206.c
@@ -0,0 +1,17 @@
+/* { dg-do run { target lp64 } } */
+
+struct {
+    unsigned long x:33;
+} s;
+typedef __typeof__(s.x + 0) uint33;
+
+int main()
+{
+  uint33 x;
+  __builtin_memset(&x, -1, sizeof x);
+  unsigned long u;
+  __builtin_memcpy(&u, &x, sizeof u);
+  if (u != -1ul)
+    __builtin_abort ();
+  return 0;
+}
-- 
2.16.4