From 1b43d4626747027599403c13ee4fed0bac5a255c Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Mon, 23 Oct 2023 15:08:19 -0700
Subject: [PATCH] build-llvm.py: Add '--build-targets'

It can be useful to select subtargets, like 'clang' or 'llvm-ar', to
build single tools when issues are isolated to them, which can reduce
build time. This provides tangible benefits when bisecting, as an issue
can be isolated down to a single commit in less time.

As part of this implementation, the build target parameter is added as a
member to LLVM_Builder and changed to a list to be more flexible and fit
in more with how customizing the builder works in the rest of tc_build.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 build-llvm.py    | 18 ++++++++++++++++--
 tc_build/llvm.py |  5 +++--
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/build-llvm.py b/build-llvm.py
index c85af110..3f245e61 100755
--- a/build-llvm.py
+++ b/build-llvm.py
@@ -40,6 +40,17 @@
 
                     '''),
                     type=str)
+parser.add_argument('--build-targets',
+                    default=['all'],
+                    help=textwrap.dedent('''\
+                    By default, the 'all' target is used as the build target for the final stage. With
+                    this option, targets such as 'distribution' could be used to generate a slimmer
+                    toolchain or targets such as 'clang' or 'llvm-ar' could be used to just test building
+                    individual tools for a bisect.
+
+                    NOTE: This only applies to the final stage build to avoid complicating tc-build internals.
+                    '''),
+                    nargs='+')
 parser.add_argument('--bolt',
                     help=textwrap.dedent('''\
                     Optimize the final clang binary with BOLT (Binary Optimization and Layout Tool), which can
@@ -526,6 +537,7 @@
     tc_build.utils.print_header('Building LLVM (bootstrap)')
 
     bootstrap = LLVMBootstrapBuilder()
+    bootstrap.build_targets = ['distribution']
     bootstrap.ccache = not args.no_ccache
     bootstrap.cmake_defines.update(common_cmake_defines)
     bootstrap.folders.build = Path(build_folder, 'bootstrap')
@@ -540,7 +552,7 @@
 
     bootstrap.check_dependencies()
     bootstrap.configure()
-    bootstrap.build('distribution')
+    bootstrap.build()
 
 # If the user did not specify CMAKE_C_FLAGS or CMAKE_CXX_FLAGS, add them as empty
 # to paste stage 2 to ensure there are no environment issues (since CFLAGS and CXXFLAGS
@@ -558,6 +570,7 @@
         instrumented = LLVMInstrumentedBuilder()
     else:
         instrumented = LLVMSlimInstrumentedBuilder()
+    instrumented.build_targets = ['all' if args.full_toolchain else 'distribution']
     instrumented.cmake_defines.update(common_cmake_defines)
     # We run the tests on the instrumented stage if the LLVM benchmark was enabled
     instrumented.check_targets = args.check_targets if 'llvm' in args.pgo else None
@@ -571,7 +584,7 @@
 
     tc_build.utils.print_header('Building LLVM (instrumented)')
     instrumented.configure()
-    instrumented.build('all' if args.full_toolchain else 'distribution')
+    instrumented.build()
 
     tc_build.utils.print_header('Generating PGO profiles')
     pgo_builders = []
@@ -648,6 +661,7 @@
     instrumented.generate_profdata()
 
 # Final build
+final.build_targets = args.build_targets
 final.check_targets = args.check_targets
 final.cmake_defines.update(common_cmake_defines)
 final.folders.build = Path(build_folder, 'final')
diff --git a/tc_build/llvm.py b/tc_build/llvm.py
index 149bec27..e0f267e8 100644
--- a/tc_build/llvm.py
+++ b/tc_build/llvm.py
@@ -27,6 +27,7 @@ def __init__(self):
 
         self.bolt = False
         self.bolt_builder = None
+        self.build_targets = ['all']
         self.ccache = False
         self.check_targets = []
         # Removes system dependency on terminfo to keep the dynamic library
@@ -133,7 +134,7 @@ def bolt_clang(self):
         if mode == 'instrumentation':
             clang_inst.unlink()
 
-    def build(self, build_target='all'):
+    def build(self):
         if not self.folders.build:
             raise RuntimeError('No build folder set for build()?')
         if not Path(self.folders.build, 'build.ninja').exists():
@@ -142,7 +143,7 @@ def build(self, build_target='all'):
             raise RuntimeError('BOLT requested without a builder?')
 
         build_start = time.time()
-        ninja_cmd = ['ninja', '-C', self.folders.build, build_target]
+        ninja_cmd = ['ninja', '-C', self.folders.build, *self.build_targets]
         self.run_cmd(ninja_cmd)
 
         if self.check_targets: