Mesa (staging/20.1): meson: Disable GCC's dead store elimination for memory zeroing custom new
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Fri May 22 23:13:03 UTC 2020
Module: Mesa
Branch: staging/20.1
Commit: 8de4ee390e354507248d4e90c54b14706ec59c0a
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=8de4ee390e354507248d4e90c54b14706ec59c0a
Author: Danylo Piliaiev <danylo.piliaiev at globallogic.com>
Date: Tue May 19 20:35:49 2020 +0300
meson: Disable GCC's dead store elimination for memory zeroing custom new
Some classes use custom new operator which zeroes memory, however gcc does
aggressive dead-store elimination which threats all writes to the memory
before the constructor as "dead stores".
For now we disable this optimization.
The new operators in question are declared via:
DECLARE_RZALLOC_CXX_OPERATORS
DECLARE_LINEAR_ZALLOC_CXX_OPERATORS
The issue was found with lto builds, however there is no guarantee that
it didn't happen with ordinary ones.
CC: <mesa-stable at lists.freedesktop.org>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2977
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/1358
Signed-off-by: Danylo Piliaiev <danylo.piliaiev at globallogic.com>
Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5104>
(cherry picked from commit 5500a2b7fc558217bbd4c2a966ab6fcadaed8b3b)
---
.pick_status.json | 2 +-
meson.build | 5 +++++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/.pick_status.json b/.pick_status.json
index 6412df0c801..e679936854e 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -985,7 +985,7 @@
"description": "meson: Disable GCC's dead store elimination for memory zeroing custom new",
"nominated": true,
"nomination_type": 0,
- "resolution": 0,
+ "resolution": 1,
"master_sha": null,
"because_sha": null
},
diff --git a/meson.build b/meson.build
index ba4fdb2a59f..434684c8bcc 100644
--- a/meson.build
+++ b/meson.build
@@ -980,6 +980,11 @@ else
'-fno-math-errno',
'-fno-trapping-math',
'-Qunused-arguments',
+ # Some classes use custom new operator which zeroes memory, however
+ # gcc does aggressive dead-store elimination which threats all writes
+ # to the memory before the constructor as "dead stores".
+ # For now we disable this optimization.
+ '-flifetime-dse=1',
]
# MinGW chokes on format specifiers and I can't get it all working
if not (cc.get_id() == 'gcc' and host_machine.system() == 'windows')
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