diff mbox series

[pushed] Darwin: Partial reversion of r14-3648 (Inits Section).

Message ID 20230910141022.89898-1-iain@sandoe.co.uk
State Unresolved
Headers
Series [pushed] Darwin: Partial reversion of r14-3648 (Inits Section). |

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Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Iain Sandoe Sept. 10, 2023, 2:10 p.m. UTC 
  Tested on x86_64-darwin21 and i686-darwin9 with both dwarfutils and
llvm-based dsymutil implementations.  Pushed to trunk, thanks
Iain

--- 8< ---

Although the Darwin ABI places both hot and cold partitions in the same
section (the linker can partition by name), this does not work with the
current dwarf2out implementation.

Since we do see global initialization code getting hot/cold splits, this
patch places the cold parts into text_cold, and keeps the hot part in
the correct Init section per ABI.

TODO: figure out a way to allow us to match the ABI fully.

gcc/ChangeLog:

	* config/darwin.cc (darwin_function_section): Place unlikely
	executed global init code into the standard cold section.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
---
 gcc/config/darwin.cc | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
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Patch

diff --git a/gcc/config/darwin.cc b/gcc/config/darwin.cc
index 95d6194cf22..154a2b2755a 100644
--- a/gcc/config/darwin.cc
+++ b/gcc/config/darwin.cc
@@ -3893,19 +3893,22 @@  darwin_function_section (tree decl, enum node_frequency freq,
   if (decl && DECL_SECTION_NAME (decl) != NULL)
     return get_named_section (decl, NULL, 0);
 
+  /* We always put unlikely executed stuff in the cold section; we have to put
+     this ahead of the global init section, since partitioning within a section
+     breaks some assumptions made in the DWARF handling.  */
+  if (freq == NODE_FREQUENCY_UNLIKELY_EXECUTED)
+    return (use_coal) ? darwin_sections[text_cold_coal_section]
+		      : darwin_sections[text_cold_section];
+
   /* Intercept functions in global init; these are placed in separate sections.
-     FIXME: there should be some neater way to do this.  */
+     FIXME: there should be some neater way to do this, FIXME we should be able
+     to partition within a section.  */
   if (DECL_NAME (decl)
       && (startswith (IDENTIFIER_POINTER (DECL_NAME (decl)), "_GLOBAL__sub_I")
 	  || startswith (IDENTIFIER_POINTER (DECL_NAME (decl)),
 			 "__static_initialization_and_destruction")))
     return  darwin_sections[static_init_section];
 
-  /* We always put unlikely executed stuff in the cold section.  */
-  if (freq == NODE_FREQUENCY_UNLIKELY_EXECUTED)
-    return (use_coal) ? darwin_sections[text_cold_coal_section]
-		      : darwin_sections[text_cold_section];
-
   /* If we have LTO *and* feedback information, then let LTO handle
      the function ordering, it makes a better job (for normal, hot,
      startup and exit - hence the bailout for cold above).  */