From: Daniel Cederman <cederman@gaisler.com>
Date: Mon, 12 Oct 2020 06:50:35 +0000 (+0200)
Subject: sparc: Prevent atomic instructions in beginning of functions for UT700
X-Git-Tag: basepoints/gcc-13~4738
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d4aa16699d4bcf9d335a206d3d8f6c1a80142aab;p=thirdparty%2Fgcc.git

sparc: Prevent atomic instructions in beginning of functions for UT700

A call to the function might have a load instruction in the delay slot
and a load followed by an atomic function could cause a deadlock.

gcc/ChangeLog:

	* config/sparc/sparc.c (sparc_do_work_around_errata): Do not begin
	functions with atomic instruction in the UT700 errata workaround.
---

diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index 94061e111bdf..7c9b347254cf 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -1116,6 +1116,7 @@ static unsigned int
 sparc_do_work_around_errata (void)
 {
   rtx_insn *insn, *next;
+  bool find_first_useful = true;
 
   /* Force all instructions to be split into their final form.  */
   split_all_insns_noflow ();
@@ -1140,6 +1141,16 @@ sparc_do_work_around_errata (void)
       else
 	jump = NULL;
 
+      /* Do not begin function with atomic instruction.  */
+      if (sparc_fix_ut700
+	  && find_first_useful
+	  && USEFUL_INSN_P (insn))
+	{
+	  find_first_useful = false;
+	  if (atomic_insn_for_leon3_p (insn))
+	    emit_insn_before (gen_nop (), insn);
+	}
+
       /* Place a NOP at the branch target of an integer branch if it is a
 	 floating-point operation or a floating-point branch.  */
       if (sparc_fix_gr712rc