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- Add llvm-workaround-superfluous-branches.patch: hints LLVM to

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eliminate branches until gh#llvm/llvm-project#28804 is solved.

OBS-URL: https://build.opensuse.org/package/show/devel:tools:compiler/llvm15?expand=0&rev=18
This commit is contained in:
Aaron Puchert 2023-01-19 20:24:57 +00:00 committed by Git OBS Bridge
parent 04d8fe57b7
commit cdc7a41102
3 changed files with 29 additions and 11 deletions
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14
llvm-workaround-superfluous-branches.patch Normal file
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@ -0,0 +1,14 @@
diff --git a/llvm/include/llvm/Support/Casting.h b/llvm/include/llvm/Support/Casting.h
index b6bbff8..1b68640 100644
--- a/llvm/include/llvm/Support/Casting.h
+++ b/llvm/include/llvm/Support/Casting.h
@@ -605,6 +605,9 @@ LLVM_NODISCARD inline decltype(auto) dyn_cast(From &Val) {
template <typename To, typename From>
LLVM_NODISCARD inline decltype(auto) dyn_cast(From *Val) {
+#if defined(__clang__) && defined(NDEBUG)
+ __builtin_assume(Val);
+#endif
return CastInfo<To, From *>::doCastIfPossible(Val);
}

11
llvm15.changes
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@ -5,11 +5,12 @@ Sat Jan 14 14:06:38 UTC 2023 - Aaron Puchert <aaronpuchert@alice-dsl.net>
* This release contains bug-fixes for the LLVM 15.0.0 release.
This release is API and ABI compatible with 15.0.0.
- Rebase llvm-do-not-install-static-libraries.patch.
- Build stage 2 with -fno-plt if we're using LTO: since building
with -Wl,-z,now the PLT stubs are basically dead code, and
eliminating the indirection should improve code locality and
reduce BTB pressure for the quite frequent cross-DSO calls.
With LTO we should not need linker relaxation.
- Build stage 2 with -fno-plt on x86_64: since building with
-Wl,-z,now the PLT stubs are basically dead code, so eliminating
the indirection reduces the number of branches and improves code
locality for the quite frequent cross-DSO calls.
- Add llvm-workaround-superfluous-branches.patch: hints LLVM to
eliminate branches until gh#llvm/llvm-project#28804 is solved.
-------------------------------------------------------------------
Sun Dec 4 21:43:38 UTC 2022 - Aaron Puchert <aaronpuchert@alice-dsl.net>

15
llvm15.spec
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@ -367,6 +367,8 @@ Patch13: llvm-normally-versioned-libllvm.patch
Patch14: llvm-do-not-install-static-libraries.patch
# PATCH-FIX-OPENSUSE (or -UPSTREAM?): we disable RPATHs, but the test driver drops LD_LIBRARY_PATH.
Patch15: libcxx-test-library-path.patch
# PATCH-FIX-UPSTREAM (?): Work around gh#llvm/llvm-project#28804 by hinting with __builtin_assume.
Patch16: llvm-workaround-superfluous-branches.patch
Patch20: llvm_build_tablegen_component_as_shared_library.patch
Patch21: tests-use-python3.patch
Patch22: llvm-better-detect-64bit-atomics-support.patch
@ -807,6 +809,7 @@ This package contains the development files for Polly.
%patch5 -p1
%patch13 -p1
%patch14 -p1
%patch16 -p2
%patch20 -p1
%patch21 -p1
%patch22 -p1
@ -979,12 +982,12 @@ if ! ./stage1/bin/clang -c -xc -Werror -fstack-clash-protection -o /dev/null /de
then
flags=$(echo -n %flags | sed 's/-fstack-clash-protection//');
fi
# 4) Add -fno-plt: With -Wl,-z,now we don't need the PLT anymore, allowing us to
# reduce the number of branches for the quite frequent cross-DSO calls. This
# is good for code locality and reduces the pressure on the BTB.
# However, do this only when we're using LTO, since otherwise indirect
# branches have to be relaxed by the linker, which might cause regressions.
%if %{with thin_lto}
# 4) Add -fno-plt: With -Wl,-z,now the PLT is basically dead code, so we can
# now go the direct route for quite frequent cross-DSO calls. This reduces
# branches in a typical execution by ~5 percent, instructions/cycles
# by ~4 percent, and reduces pressure on the instruction cache. We do this
# only on x86_64 where it doesn't increase the code size significantly.
%ifarch x86_64
flags="$flags -fno-plt"
%endif