[nvptx] Add -mptx-comment

Add functionality that indicates which insns are added by -minit-regs, such
that for instance we have for pr53465.s:
...
        // #APP
// 9 "gcc/testsuite/gcc.c-torture/execute/pr53465.c" 1
        // Start: Added by -minit-regs=3:
        // #NO_APP
                mov.u32 %r26, 0;
        // #APP
// 9 "gcc/testsuite/gcc.c-torture/execute/pr53465.c" 1
        // End: Added by -minit-regs=3:
        // #NO_APP
...

Can be switched off using -mno-ptx-comment.

Tested on nvptx.

gcc/ChangeLog:

2022-02-21  Tom de Vries  <tdevries@suse.de>

	* config/nvptx/nvptx.cc (gen_comment): New function.
	(workaround_uninit_method_1, workaround_uninit_method_2)
	(workaround_uninit_method_3): : Use gen_comment.
	* config/nvptx/nvptx.opt (mptx-comment): New option.

2 files changed, 45 insertions, 0 deletions

diff --git a/gcc/config/nvptx/nvptx.cc b/gcc/config/nvptx/nvptx.cc
index a37a6c7..981b91f 100644
--- a/gcc/config/nvptx/nvptx.cc
+++ b/gcc/config/nvptx/nvptx.cc
@@ -5372,6 +5372,17 @@ workaround_barsyncs (void)
 }
 #endif
 
+static rtx
+gen_comment (const char *s)
+{
+  const char *sep = " ";
+  size_t len = strlen (ASM_COMMENT_START) + strlen (sep) + strlen (s) + 1;
+  char *comment = (char *) alloca (len);
+  snprintf (comment, len, "%s%s%s", ASM_COMMENT_START, sep, s);
+  return gen_rtx_ASM_INPUT_loc (VOIDmode, ggc_strdup (comment),
+				cfun->function_start_locus);
+}
+
 /* Initialize all declared regs at function entry.
    Advantage   : Fool-proof.
    Disadvantage: Potentially creates a lot of long live ranges and adds a lot
@@ -5394,6 +5405,8 @@ workaround_uninit_method_1 (void)
       gcc_assert (CONST0_RTX (GET_MODE (reg)));
 
       start_sequence ();
+      if (nvptx_comment && first != NULL)
+	emit_insn (gen_comment ("Start: Added by -minit-regs=1"));
       emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
       rtx_insn *inits = get_insns ();
       end_sequence ();
@@ -5411,6 +5424,9 @@ workaround_uninit_method_1 (void)
       else
 	insert_here = emit_insn_after (inits, insert_here);
     }
+
+  if (nvptx_comment && insert_here != NULL)
+    emit_insn_after (gen_comment ("End: Added by -minit-regs=1"), insert_here);
 }
 
 /* Find uses of regs that are not defined on all incoming paths, and insert a
@@ -5446,6 +5462,8 @@ workaround_uninit_method_2 (void)
       gcc_assert (CONST0_RTX (GET_MODE (reg)));
 
       start_sequence ();
+      if (nvptx_comment && first != NULL)
+	emit_insn (gen_comment ("Start: Added by -minit-regs=2:"));
       emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
       rtx_insn *inits = get_insns ();
       end_sequence ();
@@ -5463,6 +5481,9 @@ workaround_uninit_method_2 (void)
       else
 	insert_here = emit_insn_after (inits, insert_here);
     }
+
+  if (nvptx_comment && insert_here != NULL)
+    emit_insn_after (gen_comment ("End: Added by -minit-regs=2"), insert_here);
 }
 
 /* Find uses of regs that are not defined on all incoming paths, and insert a
@@ -5531,6 +5552,27 @@ workaround_uninit_method_3 (void)
 	}
     }
 
+  if (nvptx_comment)
+    FOR_EACH_BB_FN (bb, cfun)
+      {
+	if (single_pred_p (bb))
+	  continue;
+
+	edge e;
+	edge_iterator ei;
+	FOR_EACH_EDGE (e, ei, bb->preds)
+	  {
+	    if (e->insns.r == NULL_RTX)
+	      continue;
+	    start_sequence ();
+	    emit_insn (gen_comment ("Start: Added by -minit-regs=3:"));
+	    emit_insn (e->insns.r);
+	    emit_insn (gen_comment ("End: Added by -minit-regs=3:"));
+	    e->insns.r = get_insns ();
+	    end_sequence ();
+	  }
+      }
+
   commit_edge_insertions ();
 }
 
diff --git a/gcc/config/nvptx/nvptx.opt b/gcc/config/nvptx/nvptx.opt
index 0858007..e56ec92 100644
--- a/gcc/config/nvptx/nvptx.opt
+++ b/gcc/config/nvptx/nvptx.opt
@@ -95,3 +95,6 @@ Specify the version of the ptx version to use.
 minit-regs=
 Target Var(nvptx_init_regs) IntegerRange(0, 3) Joined UInteger Init(3)
 Initialize ptx registers.
+
+mptx-comment
+Target Var(nvptx_comment) Init(1) Undocumented