From: Richard Sandiford <richard.sandiford@arm.com>
Date: Wed, 21 Feb 2024 11:12:28 +0000 (+0000)
Subject: aarch64: Fix sibcalls involving shared-ZT0 functions
X-Git-Tag: basepoints/gcc-15~1038
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d56f590483b17c538e332097807a6c5a9225ea3;p=thirdparty%2Fgcc.git

aarch64: Fix sibcalls involving shared-ZT0 functions

In:

  void bar() __arm_inout("za");
  void foo() __arm_inout("za", "zt0") { bar(); }

foo cannot tail-call bar because foo needs to restore ZT0 after
the call.  I'd forgotten to update the ok_for_sibcall rules
to handle this when adding SME2.

Thanks to Sander de Smalen for the spot.

gcc/
	* config/aarch64/aarch64.cc (aarch64_function_ok_for_sibcall):
	Check that each individual piece of state is shared in the same
	way, rather than using an aggregate check for PSTATE.ZA.

gcc/testsuite/
	* gcc.target/aarch64/sme/sibcall_9.c: New test.
---

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index de746e28ca5a..f9cedd31bc1b 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -6334,8 +6334,10 @@ aarch64_function_ok_for_sibcall (tree, tree exp)
   tree fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
   if (aarch64_fntype_pstate_sm (fntype) & ~aarch64_cfun_incoming_pstate_sm ())
     return false;
-  if (aarch64_fntype_pstate_za (fntype) != aarch64_cfun_incoming_pstate_za ())
-    return false;
+  for (auto state : { "za", "zt0" })
+    if (bool (aarch64_cfun_shared_flags (state))
+	!= bool (aarch64_fntype_shared_flags (fntype, state)))
+      return false;
   return true;
 }
 
diff --git a/gcc/testsuite/gcc.target/aarch64/sme/sibcall_9.c b/gcc/testsuite/gcc.target/aarch64/sme/sibcall_9.c
new file mode 100644
index 000000000000..2e133c881a8a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sme/sibcall_9.c
@@ -0,0 +1,51 @@
+// { dg-options "-O2 -fno-schedule-insns -fno-schedule-insns2" }
+// { dg-final { check-function-bodies "**" "" } }
+
+#pragma GCC target "+sme2"
+
+void gen_zt0() __arm_preserves("za") __arm_out("zt0");
+void callee() __arm_inout("za");
+
+/*
+** caller_inout:
+**	...
+**	str	zt0, \[[^\n]+\]
+**	bl	callee
+**	ldr	zt0, \[[^\n]+\]
+**	...
+**	ret
+*/
+void caller_inout() __arm_inout("za", "zt0") { callee(); }
+
+/*
+** caller_in:
+**	...
+**	str	zt0, \[[^\n]+\]
+**	bl	callee
+**	ldr	zt0, \[[^\n]+\]
+**	...
+**	ret
+*/
+void caller_in() __arm_inout("za") __arm_in("zt0") { callee(); }
+
+/*
+** caller_out:
+**	...
+**	str	zt0, \[[^\n]+\]
+**	bl	callee
+**	ldr	zt0, \[[^\n]+\]
+**	...
+**	ret
+*/
+void caller_out() __arm_inout("za") __arm_in("zt0") { gen_zt0(); callee(); }
+
+/*
+** caller_preserves:
+**	...
+**	str	zt0, \[[^\n]+\]
+**	bl	callee
+**	ldr	zt0, \[[^\n]+\]
+**	...
+**	ret
+*/
+void caller_preserves() __arm_inout("za") __arm_preserves("zt0") { callee(); }