store-merging: Fix up >= 64 bit insertion [PR111015]

The following testcase shows that we mishandle bit insertion for
info->bitsize >= 64.  The problem is in using unsigned HOST_WIDE_INT
shift + subtraction + build_int_cst to compute mask, the shift invokes
UB at compile time for info->bitsize 64 and larger and e.g. on the testcase
with info->bitsize happens to compute mask of 0x3f rather than
0x3f'ffffffff'ffffffff.

The patch fixes that by using wide_int wi::mask + wide_int_to_tree, so it
handles masks in any precision (up to WIDE_INT_MAX_PRECISION ;) ).

2023-08-30  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/111015
	* gimple-ssa-store-merging.c
	(imm_store_chain_info::output_merged_store): Use wi::mask and
	wide_int_to_tree instead of unsigned HOST_WIDE_INT shift and
	build_int_cst to build BIT_AND_EXPR mask.

	* gcc.dg/pr111015.c: New test.

(cherry picked from commit 49a3b35c4068091900b657cd36e5cffd41ef0c47)

diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index 629d9ad9ab600ef969e96de97b58f6f68cdfb63a..288a73d68a6ae6dd4044faaada61e6e98b75ac1e 100644 (file)
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -4519,12 +4519,13 @@ imm_store_chain_info::output_merged_store (merged_store_group *group)
                    }
                  else if ((BYTES_BIG_ENDIAN ? start_gap : end_gap) > 0)
                    {
-                     const unsigned HOST_WIDE_INT imask
-                       = (HOST_WIDE_INT_1U << info->bitsize) - 1;
+                     wide_int imask
+                       = wi::mask (info->bitsize, false,
+                                   TYPE_PRECISION (TREE_TYPE (tem)));
                      tem = gimple_build (&seq, loc,
                                          BIT_AND_EXPR, TREE_TYPE (tem), tem,
-                                         build_int_cst (TREE_TYPE (tem),
-                                                        imask));
+                                         wide_int_to_tree (TREE_TYPE (tem),
+                                                           imask));
                    }
                  const HOST_WIDE_INT shift
                    = (BYTES_BIG_ENDIAN ? end_gap : start_gap);

diff --git a/gcc/testsuite/gcc.dg/pr111015.c b/gcc/testsuite/gcc.dg/pr111015.c
new file mode 100644 (file)
index 0000000..599a14e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111015.c
@@ -0,0 +1,28 @@
+/* PR tree-optimization/111015 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O2" } */
+
+struct S { unsigned a : 4, b : 4; unsigned __int128 c : 70; } d;
+
+__attribute__((noipa)) void
+foo (unsigned __int128 x, unsigned char y, unsigned char z)
+{
+  d.a = y;
+  d.b = z;
+  d.c = x;
+}
+
+int
+main ()
+{
+  foo (-1, 12, 5);
+  if (d.a != 12
+      || d.b != 5
+      || d.c != (-1ULL | (((unsigned __int128) 0x3f) << 64)))
+    __builtin_abort ();
+  foo (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64), 7, 11);
+  if (d.a != 7
+      || d.b != 11
+      || d.c != (0x123456789abcdef0ULL | (((unsigned __int128) 26) << 64)))
+    __builtin_abort ();
+}