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Re: [PATCH, AARCH64] Enable fuse-caller-save for AARCH64


On 19-06-14 05:53, Richard Henderson wrote:
Do we in fact make sure this isn't an ifunc resolver?  I don't immediately see
how those get wired up in the cgraph...

Richard,

using the patch below I changed the gcc/testsuite/gcc.target/i386/fuse-caller-save.c testcase to use an ifunc resolver, and observed that the fuse-caller-save optimization didn't work.

The reason the optimization doesn't work in this case is that default_binds_local_p_1 checks the ifunc attribute:
...
  /* Weakrefs may not bind locally, even though the weakref itself is always
     static and therefore local.  Similarly, the resolver for ifunc functions
     might resolve to a non-local function.
     FIXME: We can resolve the weakref case more curefuly by looking at the
     weakref alias.  */
  else if (lookup_attribute ("weakref", DECL_ATTRIBUTES (exp))
	   || (TREE_CODE (exp) == FUNCTION_DECL
	       && lookup_attribute ("ifunc", DECL_ATTRIBUTES (exp))))
    local_p = false;
...

The default_binds_local_p_1 function is used via this path in the optimization:
get_call_reg_set_usage -> get_call_cgraph_rtl_info -> decl_binds_to_current_def_p -> default_binds_local_p -> default_binds_local_p_1 .

Thanks,
- Tom


diff --git a/gcc/testsuite/gcc.target/i386/fuse-caller-save.c b/gcc/testsuite/gcc.target/i386/fuse-caller-save.c
index 4ec4995..012dc12 100644
--- a/gcc/testsuite/gcc.target/i386/fuse-caller-save.c
+++ b/gcc/testsuite/gcc.target/i386/fuse-caller-save.c
@@ -5,11 +5,18 @@
 /* Testing -fuse-caller-save optimization option.  */
 
 static int __attribute__((noinline))
-bar (int x)
+my_bar (int x)
 {
   return x + 3;
 }
 
+static void (*resolve_bar (void)) (void)
+{
+  return (void*) my_bar;
+}
+
+static int __attribute__((noinline)) __attribute__((ifunc ("resolve_bar"))) bar (int x);
+
 int __attribute__((noinline))
 foo (int y)
 {
-- 
1.9.1


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