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Add emit_bc feature #2

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Add emit_bc feature #2

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7aa9e30
Add emit_bc feature
ghvg1313 Jul 29, 2020
0ffbe39
fix ws
ghvg1313 Jul 29, 2020
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18 changes: 17 additions & 1 deletion swift/internal/compiling.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ load(
"SWIFT_FEATURE_USE_GLOBAL_MODULE_CACHE",
"SWIFT_FEATURE_VFSOVERLAY",
"SWIFT_FEATURE_SPLIT_DERIVED_FILES_GENERATION",
"SWIFT_FEATURE_EMIT_BC",
)
load(":features.bzl", "are_all_features_enabled", "is_feature_enabled")
load(":providers.bzl", "SwiftInfo", "create_swift_info")
Expand Down Expand Up @@ -93,11 +94,21 @@ def compile_action_configs():
# Emit object file(s).
swift_toolchain_config.action_config(
actions = [swift_action_names.COMPILE],
not_features = [SWIFT_FEATURE_EMIT_BC],
configurators = [
swift_toolchain_config.add_arg("-emit-object"),
],
),

# Emit bitcode file
swift_toolchain_config.action_config(
actions = [swift_action_names.COMPILE],
features = [SWIFT_FEATURE_EMIT_BC],
configurators = [
swift_toolchain_config.add_arg("-emit-bc"),
],
),

# Add the single object file or object file map, whichever is needed.
swift_toolchain_config.action_config(
actions = [swift_action_names.COMPILE],
Expand Down Expand Up @@ -1567,10 +1578,15 @@ def _declare_compile_outputs(
user_compile_flags = user_compile_flags,
)

if not output_nature.emits_multiple_objects:
emit_bc = is_feature_enabled(
feature_configuration = feature_configuration,
feature_name = SWIFT_FEATURE_EMIT_BC,
)
if not output_nature.emits_multiple_objects or emit_bc:
# If we're emitting a single object, we don't use an object map; we just
# declare the output file that the compiler will generate and there are
# no other partial outputs.
# If emit_bc is on, only one bitcode file is emitted
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why?

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tried output-file-map, it doesn't seem to work with emic_bc, -### revealed it just ignore the output option and default to module-name.bc

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even with num-threads set? curious.

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@ghvg1313 ghvg1313 Jul 30, 2020 •
edited
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OK I'm missing something here

  • with num-threads on, swift will actually try to output multiple bc files, except that I can't find an option to control the output location, whatever client option I provide it just ignores it and output to the root
  • with single threaded wmo, it will behave like buck did, this seems intentional, I'm just gonna disable threading during bc_merge pipeline I think

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When you say root what do you mean?

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bazel exec root
so swiftc -emit-bc -wmo -num-threads 6 -output-file-map output.json a.swift b.swift-### will get you swiftc- frontend -emit-bc ... a.bc b.bc
Doesn't matter what you put in output.json

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Interesting. Pretty fine with the single object file output if that makes things easier.

object_files = [derived_files.whole_module_object_file(
actions = actions,
target_name = target_name,
Expand Down
4 changes: 4 additions & 0 deletions swift/internal/feature_names.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -188,3 +188,7 @@ SWIFT_FEATURE_SUPPORTS_PRIVATE_DEPS = "swift.supports_private_deps"
# `*.swiftmodule` and `*-Swift.h` are generated with a separate action
# rather than as part of the compilation.
SWIFT_FEATURE_SPLIT_DERIVED_FILES_GENERATION = "swift.split_derived_files_generation"

# If enabled, Swift compilation will produce LLVM bitcode instead of object file
# the output will share the same name as the object file (file.o)
SWIFT_FEATURE_EMIT_BC = "swift.emit_bc"