[PATCH] Fix up remove_partial_avx_dependency (PR target/89474)

[Jakub Jelinek]

Hi!

The following patch fixes two issues in the new rpad pass.
One is that the insertion at the start of a basic block didn't work properly
if the basic block didn't contain any non-NOTE/non-DEBUG_INSN instructions.
next_nonnote_nondebug_insn hapilly turns through into another basic block
and the insertion can insert an instruction in between basic blocks or into
a different basic block from where we wanted to emit it.
I believe we want to emit it after CODE_LABEL, after NOTE_INSN_BASIC_BLOCK
and if possible, after debug insns in there, the patch emits it before the
first normal insn in the bb if any, or after the BB_END (thus extending
BB_END).

Another issue is that it is quite weird/dangerous to add the v4sf_const0
pseudo uses in lots of places in the IL, register those changes with df,
then do df_analyze with different flags and finally emit the setter.
I understand the goal was not to do df_analyze etc. in the usual case where
there are no instructions that need this treatment.  This patch does the
df_analyze at the spot we find the first insn, but before we actually change
that instruction, so the changes are after the df_analyze.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2019-02-25  Jakub Jelinek  <jakub@redhat.com>

	PR target/89474
	* config/i386/i386.c (remove_partial_avx_dependency): Call
	df_analyze etc. before creation of the v4sf_const0 pseudo, rather than
	after changing possibly many instructions to use that pseudo.  Fix up
	insertion of v4sf_const0 setter at the start of bb.

	* gcc.target/i386/pr89474.c: New test.

--- gcc/config/i386/i386.c.jj	2019-02-22 23:02:47.805117610 +0100
+++ gcc/config/i386/i386.c	2019-02-25 14:20:05.793608879 +0100
@@ -2835,7 +2835,14 @@ remove_partial_avx_dependency (void)
 	    continue;
 
 	  if (!v4sf_const0)
-	    v4sf_const0 = gen_reg_rtx (V4SFmode);
+	    {
+	      calculate_dominance_info (CDI_DOMINATORS);
+	      df_set_flags (DF_DEFER_INSN_RESCAN);
+	      df_chain_add_problem (DF_DU_CHAIN | DF_UD_CHAIN);
+	      df_md_add_problem ();
+	      df_analyze ();
+	      v4sf_const0 = gen_reg_rtx (V4SFmode);
+	    }
 
 	  /* Convert PARTIAL_XMM_UPDATE_TRUE insns, DF -> SF, SF -> DF,
 	     SI -> SF, SI -> DF, DI -> SF, DI -> DF, to vec_dup and
@@ -2883,12 +2890,6 @@ remove_partial_avx_dependency (void)
 
   if (v4sf_const0)
     {
-      calculate_dominance_info (CDI_DOMINATORS);
-      df_set_flags (DF_DEFER_INSN_RESCAN);
-      df_chain_add_problem (DF_DU_CHAIN | DF_UD_CHAIN);
-      df_md_add_problem ();
-      df_analyze ();
-
       /* (Re-)discover loops so that bb->loop_father can be used in the
 	 analysis below.  */
       loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
@@ -2904,11 +2905,23 @@ remove_partial_avx_dependency (void)
 	bb = get_immediate_dominator (CDI_DOMINATORS,
 				      bb->loop_father->header);
 
-      insn = BB_HEAD (bb);
-      if (!NONDEBUG_INSN_P (insn))
-	insn = next_nonnote_nondebug_insn (insn);
       set = gen_rtx_SET (v4sf_const0, CONST0_RTX (V4SFmode));
-      set_insn = emit_insn_before (set, insn);
+
+      insn = BB_HEAD (bb);
+      while (insn && !NONDEBUG_INSN_P (insn))
+	{
+	  if (insn == BB_END (bb))
+	    {
+	      insn = NULL;
+	      break;
+	    }
+	  insn = NEXT_INSN (insn);
+	}
+      if (insn == BB_HEAD (bb))
+        set_insn = emit_insn_before (set, insn);
+      else
+	set_insn = emit_insn_after (set,
+				    insn ? PREV_INSN (insn) : BB_END (bb));
       df_insn_rescan (set_insn);
       df_process_deferred_rescans ();
       loop_optimizer_finalize ();
--- gcc/testsuite/gcc.target/i386/pr89474.c.jj	2019-02-25 14:21:51.651867104 +0100
+++ gcc/testsuite/gcc.target/i386/pr89474.c	2019-02-25 14:21:34.373151405 +0100
@@ -0,0 +1,14 @@
+/* PR target/89474 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -mavx" } */
+
+int a;
+void foo (double);
+int baz (void);
+
+void
+bar (void)
+{
+  while (baz ())
+    foo (a);
+}

	Jakub