PKGBUILDs/extra/js78/0001-Fixes-for-LTO-PGO-support.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: "Jan Alexander Steffens (heftig)" <jan.steffens@gmail.com>
Date: Tue, 17 Nov 2020 22:45:47 +0100
Subject: [PATCH] Fixes for LTO+PGO support

Cherry-picked from Firefox Nightly.
---
 build/moz.configure/lto-pgo.configure |  7 +++++--
 config/makefiles/rust.mk              | 21 +++++++++++++++++----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/build/moz.configure/lto-pgo.configure b/build/moz.configure/lto-pgo.configure
index 366c6691f7d11..e5342a037ee92 100644
--- a/build/moz.configure/lto-pgo.configure
+++ b/build/moz.configure/lto-pgo.configure
@@ -229,7 +229,10 @@ def lto(value, c_compiler, ld64_known_good, target, instrumented_build):
             # instruction sets.
         else:
             num_cores = multiprocessing.cpu_count()
-            cflags.append("-flto")
+            if len(value) and value[0].lower() == 'full':
+                cflags.append("-flto")
+            else:
+                cflags.append("-flto=thin")
             cflags.append("-flifetime-dse=1")
 
             ldflags.append("-flto=%s" % num_cores)
@@ -258,6 +261,6 @@ set_config('MOZ_LTO', lto.enabled)
 set_define('MOZ_LTO', lto.enabled)
 set_config('MOZ_LTO_CFLAGS', lto.cflags)
 set_config('MOZ_LTO_LDFLAGS', lto.ldflags)
-set_config('MOZ_LTO_RUST', lto.rust_lto)
+set_config('MOZ_LTO_RUST_CROSS', lto.rust_lto)
 add_old_configure_assignment('MOZ_LTO_CFLAGS', lto.cflags)
 add_old_configure_assignment('MOZ_LTO_LDFLAGS', lto.ldflags)
diff --git a/config/makefiles/rust.mk b/config/makefiles/rust.mk
index f4475054f8979..f19dfbc72fad0 100644
--- a/config/makefiles/rust.mk
+++ b/config/makefiles/rust.mk
@@ -59,17 +59,19 @@ cargo_rustc_flags = $(CARGO_RUSTCFLAGS)
 ifndef DEVELOPER_OPTIONS
 ifndef MOZ_DEBUG_RUST
 # Enable link-time optimization for release builds, but not when linking
-# gkrust_gtest.
+# gkrust_gtest. And not when doing cross-language LTO.
+ifndef MOZ_LTO_RUST_CROSS
 ifeq (,$(findstring gkrust_gtest,$(RUST_LIBRARY_FILE)))
 cargo_rustc_flags += -Clto
 endif
 # Versions of rust >= 1.45 need -Cembed-bitcode=yes for all crates when
 # using -Clto.
 ifeq (,$(filter 1.38.% 1.39.% 1.40.% 1.41.% 1.42.% 1.43.% 1.44.%,$(RUSTC_VERSION)))
 RUSTFLAGS += -Cembed-bitcode=yes
 endif
 endif
 endif
+endif
 
 ifdef CARGO_INCREMENTAL
 export CARGO_INCREMENTAL
@@ -195,10 +197,19 @@ target_rust_ltoable := force-cargo-library-build
 target_rust_nonltoable := force-cargo-test-run force-cargo-library-check $(foreach b,build check,force-cargo-program-$(b))
 
 ifdef MOZ_PGO_RUST
-rust_pgo_flags := $(if $(MOZ_PROFILE_GENERATE),-C profile-generate=$(topobjdir)) $(if $(MOZ_PROFILE_USE),-C profile-use=$(PGO_PROFILE_PATH))
+ifdef MOZ_PROFILE_GENERATE
+rust_pgo_flags := -C profile-generate=$(topobjdir)
+# The C compiler may be passed extra llvm flags for PGO that we also want to pass to rust as well.
+# In PROFILE_GEN_CFLAGS, they look like "-mllvm foo", and we want "-C llvm-args=foo", so first turn
+# "-mllvm foo" into "-mllvm:foo" so that it becomes a unique argument, that we can then filter for,
+# excluding other flags, and then turn into the right string.
+rust_pgo_flags += $(patsubst -mllvm:%,-C llvm-args=%,$(filter -mllvm:%,$(subst -mllvm ,-mllvm:,$(PROFILE_GEN_CFLAGS))))
+else # MOZ_PROFILE_USE
+rust_pgo_flags := -C profile-use=$(PGO_PROFILE_PATH)
+endif
 endif
 
-$(target_rust_ltoable): RUSTFLAGS:=$(rustflags_override) $(rustflags_sancov) $(RUSTFLAGS) $(if $(MOZ_LTO_RUST),-Clinker-plugin-lto) $(rust_pgo_flags)
+$(target_rust_ltoable): RUSTFLAGS:=$(rustflags_override) $(rustflags_sancov) $(RUSTFLAGS) $(if $(MOZ_LTO_RUST_CROSS),-Clinker-plugin-lto) $(rust_pgo_flags)
 $(target_rust_nonltoable): RUSTFLAGS:=$(rustflags_override) $(rustflags_sancov) $(RUSTFLAGS)
 
 TARGET_RECIPES := $(target_rust_ltoable) $(target_rust_nonltoable)
@@ -312,17 +323,19 @@ $(RUST_LIBRARY_FILE): force-cargo-library-build
 # When we are building in --enable-release mode; we add an additional check to confirm
 # that we are not importing any networking-related functions in rust code. This reduces
 # the chance of proxy bypasses originating from rust code.
-# The check only works when rust code is built with -Clto.
+# The check only works when rust code is built with -Clto but without MOZ_LTO_RUST_CROSS.
 # Sanitizers and sancov also fail because compiler-rt hooks network functions.
 ifndef MOZ_PROFILE_GENERATE
 ifeq ($(OS_ARCH), Linux)
 ifeq (,$(rustflags_sancov)$(MOZ_ASAN)$(MOZ_TSAN)$(MOZ_UBSAN))
+ifndef MOZ_LTO_RUST_CROSS
 ifneq (,$(filter -Clto,$(cargo_rustc_flags)))
 	$(call py_action,check_binary,--target --networking $@)
 endif
 endif
 endif
 endif
+endif
 
 force-cargo-library-check:
 	$(call CARGO_CHECK) --lib $(cargo_target_flag) $(rust_features_flag)