From: Kewen Lin <linkw@linux.ibm.com>
Date: Wed, 22 Sep 2021 00:13:57 +0000 (-0500)
Subject: ipa-fnsummary: Remove inconsistent bp_pack_value
X-Git-Tag: releases/gcc-11.3.0~869
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cc11a171eee059b645870f2e208c530f301239c9;p=thirdparty%2Fgcc.git

ipa-fnsummary: Remove inconsistent bp_pack_value

There is one inconsistent bit-field streaming out and in.
On the side of streaming in:

    bp_pack_value (&bp, info->inlinable, 1);
    bp_pack_value (&bp, false, 1);
    bp_pack_value (&bp, info->fp_expressions, 1);

while on the side of the streaming out:

    info->inlinable = bp_unpack_value (&bp, 1);
    info->fp_expressions = bp_unpack_value (&bp, 1)

The removal of Cilk Plus support r8-4956 missed to remove
the streaming out of the bit, instead just change the value
for streaming out to be always false.

By hacking fp_expression_p to always return true, I can see
it reads the wrong fp_expressions value (false) out in wpa.

GCC12 adopts commit 63c6446f77b9001d26f973114450d790749f282b
which removes the inconsistent streaming out instead.

gcc/ChangeLog:

	* ipa-fnsummary.c (inline_read_section): Unpack a dummy bit
	to keep consistent with the side of streaming out.
---

diff --git a/gcc/ipa-fnsummary.c b/gcc/ipa-fnsummary.c
index 18bbae145b9b..bf635c1f78aa 100644
--- a/gcc/ipa-fnsummary.c
+++ b/gcc/ipa-fnsummary.c
@@ -4403,13 +4403,20 @@ inline_read_section (struct lto_file_decl_data *file_data, const char *data,
       bp = streamer_read_bitpack (&ib);
       if (info)
 	{
-          info->inlinable = bp_unpack_value (&bp, 1);
-          info->fp_expressions = bp_unpack_value (&bp, 1);
+	  info->inlinable = bp_unpack_value (&bp, 1);
+	  /* On the side of streaming out, there is still one bit
+	     streamed out between inlinable and fp_expressions bits,
+	     which was used for cilk+ before but now always false.
+	     To remove the bit packing need to bump LTO minor version,
+	     so unpack a dummy bit here to keep consistent instead.  */
+	  bp_unpack_value (&bp, 1);
+	  info->fp_expressions = bp_unpack_value (&bp, 1);
 	}
       else
 	{
-          bp_unpack_value (&bp, 1);
-          bp_unpack_value (&bp, 1);
+	  bp_unpack_value (&bp, 1);
+	  bp_unpack_value (&bp, 1);
+	  bp_unpack_value (&bp, 1);
 	}
 
       count2 = streamer_read_uhwi (&ib);