[committed] [PR target/111362] Fix compare-debug issue with mode switching

The issue here is the code we emit for mode-switching can change when -g is
added to the command line.  This is caused by processing debug notes occurring
after a call which is the last real statement in a basic block.

Without -g the CALL_INSN is literally the last insn in the block and the loop
exits.  If mode switching after the call is needed, it'll be handled as we
process outgoing edges.

With -g the loop iterates again and in the processing of the node the backend
signals that a mode switch is necessary.

I pondered fixing this in the target, but the better fix is to ignore the debug
notes in the insn stream.

I did a cursory review of some of the other compare-debug failures, but did not
immediately see others which would likely be fixed by this change.  Sigh.

Anyway, bootstrapped and regression tested on x86.  Regression tested on rv64
as well.

	PR target/111362
gcc/
	* mode-switching.cc (optimize_mode_switching): Only process
	NONDEBUG insns.

gcc/testsuite

	* gcc.target/riscv/compare-debug-1.c: New test.
	* gcc.target/riscv/compare-debug-2.c: New test.

gcc/mode-switching.cc

@@ -959,7 +959,7 @@ optimize_mode_switching (void)
 
 	  FOR_BB_INSNS (bb, insn)
 	    {
-	      if (INSN_P (insn))
+	      if (NONDEBUG_INSN_P (insn))
 		{
 		  int mode = targetm.mode_switching.needed (e, insn, live_now);
 		  rtx link;

gcc/testsuite/gcc.target/riscv/compare-debug-1.c

@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-ch --param=max-completely-peel-times=0 -march=rv64iv -mabi=lp64d -fcompare-debug" } */
+
+
+void
+foo(void) {
+  for (unsigned i = 0; i < sizeof(foo); i++)
+    __builtin_printf("%d", i);
+}

gcc/testsuite/gcc.target/riscv/compare-debug-2.c

@@ -0,0 +1,3 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-ch --param=max-completely-peel-times=0 -march=rv64iv -mabi=lp64d -fno-dce -fschedule-insns -fcompare-debug" } */
+#include "compare-debug-1.c"