From 1fce5932a3af575cd02c1d2b786dd1b39b922ebe Mon Sep 17 00:00:00 2001
From: Richard Sandiford <richard.sandiford@arm.com>
Date: Wed, 14 Apr 2021 20:06:44 +0100
Subject: [PATCH] Better const_vector printing

Looking at PR99929 showed that we weren't dumping enough information
about variable-length CONST_VECTORs.  Something like:

  (const_vector:VNx4SI [(const_int 1) (const_int 0)])

could be either:

(a) 1, 0, 1, 0, repeating
(b) 1 followed by all zeros

This patch adds more information to the dumps.  There are four cases:

(a) above:

    (const_vector:VNx4SI repeat [
      (const_int 1)
      (const_int 0)
    ])

(b) above:

    (const_vector:VNx4SI [
      (const_int 1)
      repeat [
        (const_int 0)
      ]
    ])

a single stepped sequence:

    (const_vector:VNx4SI [
      (const_int 0)
      stepped [
        (const_int 1)
        (const_int 2)
      ]
    ])

interleaved stepped sequences:

    (const_vector:VNx4SI [
      (const_int 0)
      (const_int 40)
      stepped (interleave 2) [
        (const_int 1)
        (const_int 41)
        (const_int 2)
        (const_int 42)
      ]
    ])

There are probably better syntaxes, but hopefully this is at least
an improvement on the status quo.

gcc/
	* print-rtl.c (rtx_writer::print_rtx_operand_codes_E_and_V): Print
	more information about variable-length CONST_VECTORs.
---
 gcc/print-rtl.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/gcc/print-rtl.c b/gcc/print-rtl.c
index c7982bce507..081fc50fab8 100644
--- a/gcc/print-rtl.c
+++ b/gcc/print-rtl.c
@@ -370,6 +370,10 @@ rtx_writer::print_rtx_operand_codes_E_and_V (const_rtx in_rtx, int idx)
       print_rtx_head, m_indent * 2, "");
       m_sawclose = 0;
     }
+  if (GET_CODE (in_rtx) == CONST_VECTOR
+      && !GET_MODE_NUNITS (GET_MODE (in_rtx)).is_constant ()
+      && CONST_VECTOR_DUPLICATE_P (in_rtx))
+    fprintf (m_outfile, " repeat");
   fputs (" [", m_outfile);
   if (XVEC (in_rtx, idx) != NULL)
     {
@@ -377,12 +381,32 @@ rtx_writer::print_rtx_operand_codes_E_and_V (const_rtx in_rtx, int idx)
       if (XVECLEN (in_rtx, idx))
 	m_sawclose = 1;
 
+      int barrier = XVECLEN (in_rtx, idx);
+      if (GET_CODE (in_rtx) == CONST_VECTOR
+	  && !GET_MODE_NUNITS (GET_MODE (in_rtx)).is_constant ())
+	barrier = CONST_VECTOR_NPATTERNS (in_rtx);
+
       for (int j = 0; j < XVECLEN (in_rtx, idx); j++)
 	{
 	  int j1;
 
+	  if (j == barrier)
+	    {
+	      fprintf (m_outfile, "\n%s%*s",
+		       print_rtx_head, m_indent * 2, "");
+	      if (!CONST_VECTOR_STEPPED_P (in_rtx))
+		fprintf (m_outfile, "repeat [");
+	      else if (CONST_VECTOR_NPATTERNS (in_rtx) == 1)
+		fprintf (m_outfile, "stepped [");
+	      else
+		fprintf (m_outfile, "stepped (interleave %d) [",
+			 CONST_VECTOR_NPATTERNS (in_rtx));
+	      m_indent += 2;
+	    }
+
 	  print_rtx (XVECEXP (in_rtx, idx, j));
-	  for (j1 = j + 1; j1 < XVECLEN (in_rtx, idx); j1++)
+	  int limit = MIN (barrier, XVECLEN (in_rtx, idx));
+	  for (j1 = j + 1; j1 < limit; j1++)
 	    if (XVECEXP (in_rtx, idx, j) != XVECEXP (in_rtx, idx, j1))
 	      break;
 
@@ -393,6 +417,12 @@ rtx_writer::print_rtx_operand_codes_E_and_V (const_rtx in_rtx, int idx)
 	    }
 	}
 
+      if (barrier < XVECLEN (in_rtx, idx))
+	{
+	  m_indent -= 2;
+	  fprintf (m_outfile, "\n%s%*s]", print_rtx_head, m_indent * 2, "");
+	}
+
       m_indent -= 2;
     }
   if (m_sawclose)