[gcc r13-6083] tree-ssa-dse: Fix up handling of lhs of internal calls [PR108657]

[gcc r13-6083] tree-ssa-dse: Fix up handling of lhs of internal calls [PR108657]

[Jakub Jelinek]

https://gcc.gnu.org/g:866555b170016c49beb869a78cbecdeb07c63135

commit r13-6083-g866555b170016c49beb869a78cbecdeb07c63135
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Feb 16 15:35:05 2023 +0100

    tree-ssa-dse: Fix up handling of lhs of internal calls [PR108657]
    
    The r13-1778 PR106378 tree-ssa-dse change didn't just add special support
    for IFN_LEN_STORE and IFN_MASK_STORE internal function calls as I believe
    was intended, but given that the function was
    if (is builtin) { ... }
    else if (lhs present and non-SSA_NAME) { ... }
    return false;
    and it added a new
    else if (is internal builtin) { ... }
    in between the two, the last if used to be done before on all stmts
    with non-SSA_NAME lhs except for calls to builtin functions, but newly
    isn't done also for calls to internal functions.  In the testcase
    the important internal function is .DEFERRED_INIT, which often has
    non-SSA_NAME lhs, and the change resulted in them no longer being DSEd,
    so a block with nothing in it left but var = .DEFERRED_INIT () and
    var = {CLOBBER} was unrolled several times.
    
    The following patch does the lhs handling for all stmts with non-SSA_NAME lhs
    unless initialize_ao_ref_for_dse handled those specially already and
    returned (which is the case for various mem* builtins which don't have
    such lhs, for some cases of calloc which again is fine,and since r13-1778
    also for IFN_LEN_STORE call and some IFN_MASK_STORE calls.
    As IFN_MASK_STORE doesn't have a lhs, the break for the !may_def_ok case
    doesn't seem to change anything, and because we've handled internal fns
    that way in the past, I think it is the right thing to do that again.
    That said, if it is inappropriate for some new ifn, I guess it could
    be added to the switch and just return false; for it instead of break;.
    
    2023-02-16  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/108657
            * tree-ssa-dse.cc (initialize_ao_ref_for_dse): If lhs of stmt
            exists and is not a SSA_NAME, call ao_ref_init even if the stmt
            is a call to internal or builtin function.
    
            * gcc.dg/pr108657.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/pr108657.c | 31 +++++++++++++++++++++++++++++++
 gcc/tree-ssa-dse.cc             |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/pr108657.c b/gcc/testsuite/gcc.dg/pr108657.c
new file mode 100644
index 00000000000..37d0b8e863f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108657.c
@@ -0,0 +1,31 @@
+/* PR tree-optimization/108657 */
+/* { dg-do run } */
+/* { dg-options "-O3 -ftrivial-auto-var-init=zero" } */
+
+int c, e, f;
+static int *d = &c;
+
+__attribute__((noipa)) void
+foo (void)
+{
+  if (c != 1)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  for (c = 1; c >= 0; c--)
+    {
+      e = 0;
+      for (int j = 0; j <= 2; j++)
+	{
+	  short k[1];
+	  if (e)
+	    break;
+	  e ^= f;
+	}
+    }
+  *d = 1;
+  foo ();
+}
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 46ab57d5754..4f8a44fbba0 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -177,7 +177,7 @@ initialize_ao_ref_for_dse (gimple *stmt, ao_ref *write, bool may_def_ok = false)
 	default:;
 	}
     }
-  else if (tree lhs = gimple_get_lhs (stmt))
+  if (tree lhs = gimple_get_lhs (stmt))
     {
       if (TREE_CODE (lhs) != SSA_NAME)
 	{