Makefile.rules: Use a shared clang module cache directory.

[aprantl]

Summary

Just to be safe, up until now each test used its own Clang module
cache directory. Since the compiler within one testsuite doesn't
change it is just as safe to share a clang module directory inside the
LLDB test build directory. This saves us from compiling tens of
gigabytes of redundant Darwin and Foundation .pcm files and also
speeds up running the test suite quite significantly.

rdar://problem/36002081

[JDevlieghere]

LGTM

[aprantl]

Small bugfix + an error message that would have caught it.

[JDevlieghere]

Looks like the sed expression is not working on Windows: http://lab.llvm.org:8014/builders/lldb-x64-windows-ninja/builds/1418/steps/test/logs/stdio

lit/lit.cfg.py

 # -*- Python -*-
 
 import os
 import sys
 import re
 import platform
+import shutil
 import subprocess
 
-
 import lit.util
 import lit.formats
 from lit.llvm import llvm_config
 from lit.llvm.subst import FindTool
 from lit.llvm.subst import ToolSubst
 
 # name: The name of this test suite.
 config.name = 'LLDB'

 # Run llvm-config and add automatically add features for whether we have
 # assertions enabled, whether we are in debug mode, and what targets we
 # are built for.
 llvm_config.feature_config(
     [('--assertion-mode', {'ON': 'asserts'}),
      ('--build-mode', {'DEBUG': 'debug'}),
      ('--targets-built', calculate_arch_features)
      ])
+
+# Clean the module caches in the test build directory.  This is
+# necessary in an incremental build whenever clang changes underneath,
+# so doing it once per lit.py invocation is close enough.
+for i in ['module-cache-clang']:
+    cachedir = os.path.join(config.llvm_obj_root, 'lldb-test-build.noindex', i)
+    if os.path.isdir(cachedir):
+        print("Deleting module cache at %s."%cachedir)
+        shutil.rmtree(cachedir)

packages/Python/lldbsuite/test/make/Makefile.rules

 # Uncomment line below for debugging shell commands
 # SHELL = /bin/sh -x
 
 SRCDIR := $(shell dirname $(firstword $(MAKEFILE_LIST)))/
 BUILDDIR := $(shell pwd)
 THIS_FILE_DIR := $(shell dirname $(lastword $(MAKEFILE_LIST)))/
 LLDB_BASE_DIR := $(THIS_FILE_DIR)../../../../../
 
-
 #----------------------------------------------------------------------
 # If OS is not defined, use 'uname -s' to determine the OS name.
 #
 # uname on Windows gives "windows32" or "server version windows32", but most
 # environments standardize on "Windows_NT", so we'll make it consistent here.
 # When running tests from Visual Studio, the environment variable isn't
 # inherited all the way down to the process spawned for make.
 #----------------------------------------------------------------------

 else
   CFLAGS_NO_DEBUG = -O0 $(ARCHFLAG)$(ARCH) $(FRAMEWORK_INCLUDES) $(ARCH_CFLAGS) $(CFLAGS_EXTRAS)
 endif
 
 ifeq "$(MAKE_DWO)" "YES"
   CFLAGS += -gsplit-dwarf
 endif
 
+# Use a shared module cache when building in the default test build directory.
+ifeq "$(findstring lldb-test-build.noindex, $(BUILDDIR))" ""
 CLANG_MODULE_CACHE_DIR := $(BUILDDIR)/module-cache
+else
+CLANG_MODULE_CACHE_DIR := $(shell echo "$(BUILDDIR)" | sed 's/lldb-test-build.noindex.*/lldb-test-build.noindex\/module-cache-clang/')
+endif
+
+ifeq "$(CLANG_MODULE_CACHE_DIR)" ""
+$(error failed to set the shared clang module cache dir)
+endif
 
 MANDATORY_MODULE_BUILD_CFLAGS := -fmodules -gmodules -fmodules-cache-path=$(CLANG_MODULE_CACHE_DIR)
 
 ifeq "$(MAKE_GMODULES)" "YES"
   CFLAGS += $(MANDATORY_MODULE_BUILD_CFLAGS)
   CXXFLAGS += $(MANDATORY_MODULE_BUILD_CFLAGS)
   ifeq "$(OS)" "Darwin"
     CXXFLAGS += -fcxx-modules