[llvm] [Bazel] Make LLVM config headers configurable (PR #126729)

[Aaron Siddhartha Mondal via llvm-commits]

================
@@ -2,118 +2,331 @@
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-"""Defines variables that use selects to configure LLVM based on platform."""
+"""Substitutions for use in templates related to the LLVM configuration."""
 
+load("@bazel_skylib//lib:selects.bzl", "selects")
 load(
     "//:vars.bzl",
     "LLVM_VERSION_MAJOR",
     "LLVM_VERSION_MINOR",
     "LLVM_VERSION_PATCH",
     "PACKAGE_VERSION",
 )
+load("//llvm:targets.bzl", "llvm_targets")
+load(
+    ":cmakehelpers.bzl",
+    "cmakedefine",
+    "cmakedefine01",
+    "cmakedefine01_off",
+    "cmakedefine01_on",
+    "cmakedefine_set",
+    "cmakedefine_string",
+    "cmakedefine_unset",
+)
 
-def native_arch_defines(arch, triple):
-    return [
-        r'LLVM_NATIVE_ARCH=\"{}\"'.format(arch),
-        "LLVM_NATIVE_ASMPARSER=LLVMInitialize{}AsmParser".format(arch),
-        "LLVM_NATIVE_ASMPRINTER=LLVMInitialize{}AsmPrinter".format(arch),
-        "LLVM_NATIVE_DISASSEMBLER=LLVMInitialize{}Disassembler".format(arch),
-        "LLVM_NATIVE_TARGET=LLVMInitialize{}Target".format(arch),
-        "LLVM_NATIVE_TARGETINFO=LLVMInitialize{}TargetInfo".format(arch),
-        "LLVM_NATIVE_TARGETMC=LLVMInitialize{}TargetMC".format(arch),
-        "LLVM_NATIVE_TARGETMCA=LLVMInitialize{}TargetMCA".format(arch),
-        r'LLVM_HOST_TRIPLE=\"{}\"'.format(triple),
-        r'LLVM_DEFAULT_TARGET_TRIPLE=\"{}\"'.format(triple),
-    ]
-
-posix_defines = [
-    "LLVM_ON_UNIX=1",
-    "HAVE_BACKTRACE=1",
-    "BACKTRACE_HEADER=<execinfo.h>",
-    r'LTDL_SHLIB_EXT=\".so\"',
-    r'LLVM_PLUGIN_EXT=\".so\"',
-    "LLVM_ENABLE_THREADS=1",
-    "HAVE_DEREGISTER_FRAME=1",
-    "HAVE_LIBPTHREAD=1",
-    "HAVE_PTHREAD_GETNAME_NP=1",
-    "HAVE_PTHREAD_H=1",
-    "HAVE_PTHREAD_SETNAME_NP=1",
-    "HAVE_REGISTER_FRAME=1",
-    "HAVE_SETENV_R=1",
-    "HAVE_STRERROR_R=1",
-    "HAVE_SYSEXITS_H=1",
-    "HAVE_UNISTD_H=1",
-]
-
-linux_defines = posix_defines + [
-    "_GNU_SOURCE",
-    "HAVE_MALLINFO=1",
-    "HAVE_SBRK=1",
-    "HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=1",
-]
-
-macos_defines = posix_defines + [
-    "HAVE_MACH_MACH_H=1",
-    "HAVE_MALLOC_MALLOC_H=1",
-    "HAVE_MALLOC_ZONE_STATISTICS=1",
-    "HAVE_PROC_PID_RUSAGE=1",
-    "HAVE_UNW_ADD_DYNAMIC_FDE=1",
-]
-
-win32_defines = [
-    # Windows system library specific defines.
-    "_CRT_SECURE_NO_DEPRECATE",
-    "_CRT_SECURE_NO_WARNINGS",
-    "_CRT_NONSTDC_NO_DEPRECATE",
-    "_CRT_NONSTDC_NO_WARNINGS",
-    "_SCL_SECURE_NO_DEPRECATE",
-    "_SCL_SECURE_NO_WARNINGS",
-    "UNICODE",
-    "_UNICODE",
+CONFIG_H_SUBSTITUTIONS = (
----------------
aaronmondal wrote:

Note: With the exception of zlib/zstd and the extension change on macos this mirrors the previous implementation

https://github.com/llvm/llvm-project/pull/126729