The following makes sure to set alignment information on the LHS
of __builtin_assume_alignment calls even when not optimizing so
uses as arguments to builtin functions like memcpy or __atomic_load_n
can be reflected at RTL expansion time.
Bootstrap and regtest running on x86_64-unknown-linux-gnu, OK?
Thanks,
Richard.
PR tree-optimization/107389
* gimple-low.cc (lower_builtin_assume_aligned): New.
(lower_stmt): Call it.
* gcc.dg/pr107389.c: New testcase.
---
gcc/gimple-low.cc | 41 +++++++++++++++++++++++++++++++++
gcc/testsuite/gcc.dg/pr107389.c | 13 +++++++++++
2 files changed, 54 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/pr107389.c
diff --git a/gcc/gimple-low.cc b/gcc/gimple-low.cc
index 512aa9feada..f9bcb772163 100644
--- a/gcc/gimple-low.cc
+++ b/gcc/gimple-low.cc
@@ -84,6 +84,7 @@ static void lower_try_catch (gimple_stmt_iterator *, struct
lower_data *);
static void lower_gimple_return (gimple_stmt_iterator *, struct lower_data *);
static void lower_builtin_setjmp (gimple_stmt_iterator *);
static void lower_builtin_posix_memalign (gimple_stmt_iterator *);
+static void lower_builtin_assume_aligned (gimple_stmt_iterator *);
/* Lower the body of current_function_decl from High GIMPLE into Low
@@ -768,6 +769,13 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data
*data)
lower_builtin_posix_memalign (gsi);
return;
}
+ else if (DECL_FUNCTION_CODE (decl) == BUILT_IN_ASSUME_ALIGNED
+ && !optimize)
+ {
+ lower_builtin_assume_aligned (gsi);
+ data->cannot_fallthru = false;
+ return;
+ }
}
if (decl && (flags_from_decl_or_type (decl) & ECF_NORETURN))
@@ -1310,6 +1318,39 @@ lower_builtin_posix_memalign (gimple_stmt_iterator *gsi)
gsi_insert_after (gsi, stmt, GSI_NEW_STMT);
gsi_insert_after (gsi, gimple_build_label (noalign_label), GSI_NEW_STMT);
}
+
+/* Lower calls to __builtin_assume_aligned when not optimizing. */
+
+static void
+lower_builtin_assume_aligned (gimple_stmt_iterator *gsi)
+{
+ gcall *call = as_a <gcall *> (gsi_stmt (*gsi));
+
+ tree lhs = gimple_call_lhs (call);
+ if (!lhs || !POINTER_TYPE_P (TREE_TYPE (lhs)))
+ return;
+
+ tree align = gimple_call_arg (call, 1);
+ tree misalign = (gimple_call_num_args (call) > 2
+ ? gimple_call_arg (call, 2) : NULL_TREE);
+ if (!tree_fits_uhwi_p (align)
+ || (misalign && !tree_fits_uhwi_p (misalign)))
+ return;
+
+ unsigned aligni = TREE_INT_CST_LOW (align);
+ unsigned misaligni = misalign ? TREE_INT_CST_LOW (misalign) : 0;
+ if (aligni <= 1
+ || (aligni & (aligni - 1)) != 0
+ || (misaligni & ~(aligni - 1)) != 0)
+ return;
+
+ /* For lowering we simply transfer alignment information to the
+ result and leave the call otherwise unchanged, it will be elided
+ at RTL expansion time. */
+ ptr_info_def *pi = get_ptr_info (lhs);
+ set_ptr_info_alignment (pi, aligni, misaligni);
+ gsi_next (gsi);
+}
/* Record the variables in VARS into function FN. */
diff --git a/gcc/testsuite/gcc.dg/pr107389.c b/gcc/testsuite/gcc.dg/pr107389.c
new file mode 100644
index 00000000000..deb63380704
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107389.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-optimized-alias" } */
+
+unsigned foo (void *p)
+{
+ unsigned i;
+ __builtin_memcpy (&i, __builtin_assume_aligned (p, 4), sizeof (unsigned));
+ return i;
+}
+
+/* Even when not optimizing we should have alignment info on the temporary
+ feeding the memcpy. */
+/* { dg-final { scan-tree-dump "ALIGN = 4" "optimized" } } */
--
2.35.3
