Do not check gimple_call_chain in tree-ssa-alias

Jan Hubicka
Thu Nov 25 13:11:05 GMT 2021

this pach removes gimple_call_cahin checkin ref_maybe_used_by_call_p that
disables check for CONST functions.  I suppose it was meant to allow consts
to read variables from the static chain but this is not what other places
do.  The testcase:

        int a =0;
        __attribute__ ((noinline,const))
        int reta ()
                return a;
        int val = reta();
        return val+reta ();

Gets optimized to single call of reta since at least gcc 4.1.

LTO bootstrapped and regtested x86_64-linux all languages. OK?

	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): Do not check
	gimple_call_call when treating const functions.

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index cd6a0b2f67b..3c253e2843f 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -2743,9 +2743,7 @@ ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref, bool tbaa_p)
   unsigned i;
   int flags = gimple_call_flags (call);
-  /* Const functions without a static chain do not implicitly use memory.  */
-  if (!gimple_call_chain (call)
-      && (flags & (ECF_CONST|ECF_NOVOPS)))
+  if (flags & (ECF_CONST|ECF_NOVOPS))
     goto process_args;
   /* A call that is not without side-effects might involve volatile

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