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Increase LLVM inline-threshold to 5000 #130

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Merged
peterzhu2118 merged 1 commit into from
Oct 19, 2026
Merged

Increase LLVM inline-threshold to 5000 #130

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14 changes: 13 additions & 1 deletion gc/mmtk/depend
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,22 @@ $(TARGET_SO): $(MMTK_BUILD)/$(LIBMMTK_RUBY)

$(OBJS): Makefile

# A raised LLVM inline threshold for the Rust GC code: this is what fuses the
# per-object marking pipeline (work packet loop, closure trampoline, type fast
# paths, mark enqueue) into straight-line code. Without it the fast paths in
# scanning.rs stay behind real calls and the win evaporates.
#
# The flag must reach rustc either via the target-scoped RUSTFLAGS in
# MMTK_CARGO_ENV (LTO builds, see extconf.rb) or via plain RUSTFLAGS. Never
# set both: plain RUSTFLAGS has higher precedence in Cargo and would clobber
# the target-scoped flags.
MMTK_INLINE_THRESHOLD = 5000
MMTK_THRESHOLD_RUSTFLAGS = -Cllvm-args=-inline-threshold=$(MMTK_INLINE_THRESHOLD)

release/$(LIBMMTK_RUBY) debug/$(LIBMMTK_RUBY): $(RUSTSRCS) $(srcdir)/Cargo.toml $(srcdir)/Cargo.lock Makefile

release/$(LIBMMTK_RUBY):
CARGO_TARGET_DIR="." $(MMTK_CARGO_ENV) cargo build --manifest-path=$(srcdir)/Cargo.toml --release $(MMTK_CARGO_FLAGS)
CARGO_TARGET_DIR="." $(if $(MMTK_CARGO_ENV),,RUSTFLAGS="$(RUSTFLAGS) $(MMTK_THRESHOLD_RUSTFLAGS)") $(MMTK_CARGO_ENV) cargo build --manifest-path=$(srcdir)/Cargo.toml --release $(MMTK_CARGO_FLAGS)
$(MMTK_CARGO_FIXUP)

debug/$(LIBMMTK_RUBY):
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2 changes: 1 addition & 1 deletion gc/mmtk/extconf.rb
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Expand Up @@ -134,7 +134,7 @@ def filter_warnflags(cc, flags)
CFLAGS += #{cflags}
DLDFLAGS += #{ldflags}
warnflags = #{warnflags}
MMTK_CARGO_ENV = #{env}="-Clinker-plugin-lto -C target-cpu=native"
MMTK_CARGO_ENV = #{env}="-Clinker-plugin-lto -C target-cpu=native -Cllvm-args=-inline-threshold=$(MMTK_INLINE_THRESHOLD)"
MMTK_CARGO_FLAGS = --target #{lto[:host]}
MMTK_CARGO_FIXUP = mkdir -p release && cp -f #{lto[:host]}/release/$(LIBMMTK_RUBY) release/$(LIBMMTK_RUBY)
endif
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