lld: improve the `-arch` handling for MachO

[compnerd]

Summary

Use the default target triple configured by the user to determine the
default architecture for ld64.lld. Stash the architecture in the
configuration as when linking against TBDs, we will need to filter out
the symbols based upon the architecture. Treat the Haswell slice as it
is equivalent to x86_64 but with the extra Haswell extensions (e.g.
AVX2, FMA3, BMI1, etc). This will make it easier to add new
architectures in the future.

This change also changes the failure mode where an invalid -arch
parameter will result in the linker exiting without further processing.

[int3]

lgtm

lld/MachO/Driver.cpp

99

I assume the h suffix means Haswell

[Ktwu]

lld/MachO/Driver.cpp

99

Yup that's Haswell.

[compnerd]

rGfcdf7578aa697526e5eee05fb0e5390c4ef02eb9

lld/MachO/Driver.cpp

99

Yes, the x86_64h is the Haswell indicator. This allows for non-Haswell and Haswell targets to be lipo'ed into a single fat binary.

[int3]

Hey @compnerd, didn't realize that this diff would mean we needed to specify -arch in all our tests... I tried to remove that in D81802: [lld-macho] No need to explicitly specify -arch in tests but it appears that REQUIRES: x86 tests still run on non-x86 machines, because (we think) the REQUIRES line is about what targets are supported by the LLVM that we're building, and not what the host machine is running. Looking at lld-ELF and ld64, it seems that they both try to infer the architecture from the input object files, so we should probably implement that at some point. But in the meantime, could we revert to the old behavior of defaulting to x86_64 regardless of the default target triple?

[mgorny]

This change broke standalone builds of LLD:

FAILED: MachO/CMakeFiles/lldMachO2.dir/Driver.cpp.o 
/usr/lib64/ccache/bin/x86_64-pc-linux-gnu-g++ -DGTEST_HAS_RTTI=0 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -IMachO -I/var/tmp/portage/sys-devel/lld-11.0.0.9999/work/lld/MachO -I/var/tmp/portage/sys-devel/lld-11.0.0.9999/work/lld/include -Iinclude -I/usr/lib64/llvm/11/include  -O2 -pipe -fPIC -fvisibility-inlines-hidden -Werror=date-time -w -fdiagnostics-color -ffunction-sections -fdata-sections    -fno-exceptions -fno-rtti -MD -MT MachO/CMakeFiles/lldMachO2.dir/Driver.cpp.o -MF MachO/CMakeFiles/lldMachO2.dir/Driver.cpp.o.d -o MachO/CMakeFiles/lldMachO2.dir/Driver.cpp.o -c /var/tmp/portage/sys-devel/lld-11.0.0.9999/work/lld/MachO/Driver.cpp
/var/tmp/portage/sys-devel/lld-11.0.0.9999/work/lld/MachO/Driver.cpp:30:10: fatal error: llvm/Config/config.h: No such file or directory
 #include "llvm/Config/config.h"
          ^~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

lld/MachO/Driver.cpp

30

This file is not part of LLVM install, so including it breaks standalone builds.

[smeenai]

@int3, are we able to get rid of that include with D81983?

[int3]

Yup. Just did that and landed. Thanks for the heads up @mgorny

[mgorny]

Thanks for the fix.

lld/MachO/Config.h

 //===- Config.h -------------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_MACHO_CONFIG_H
 #define LLD_MACHO_CONFIG_H
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/MachO.h"
+#include "llvm/TextAPI/MachO/Architecture.h"
 
 #include <vector>
 
 namespace lld {
 namespace macho {
 
 class Symbol;
 struct SymbolPriorityEntry;
 
 struct Configuration {
   Symbol *entry;
   bool hasReexports = false;
   llvm::StringRef installName;
   llvm::StringRef outputFile;
+  llvm::MachO::Architecture arch;
   llvm::MachO::HeaderFileType outputType;
   std::vector<llvm::StringRef> searchPaths;
   llvm::DenseMap<llvm::StringRef, SymbolPriorityEntry> priorities;
 };
 
 // The symbol with the highest priority should be ordered first in the output
 // section (modulo input section contiguity constraints). Using priority
 // (highest first) instead of order (lowest first) has the convenient property

lld/MachO/Driver.cpp

 #include "lld/Common/LLVM.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Version.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/BinaryFormat/Magic.h"
+#include "llvm/Config/config.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 
 using namespace llvm;
 using namespace llvm::MachO;
for (StringRef library : {shared, archive}) {
       if (fs::exists(location))
         return location.str().str();
     }
   }
   return None;
 }
 
 static TargetInfo *createTargetInfo(opt::InputArgList &args) {
-  StringRef s = args.getLastArgValue(OPT_arch, "x86_64");
-  if (s != "x86_64")
-    error("missing or unsupported -arch " + s);
+  StringRef arch = llvm::Triple(LLVM_DEFAULT_TARGET_TRIPLE).getArchName();
+  config->arch =
+      llvm::MachO::getArchitectureFromName(args.getLastArgValue(OPT_arch, arch));
+  switch (config->arch) {
+  case llvm::MachO::AK_x86_64:
+  case llvm::MachO::AK_x86_64h:
     return createX86_64TargetInfo();
+  default:
+    fatal("missing or unsupported -arch " + args.getLastArgValue(OPT_arch));
+  }
 }
 
 static std::vector<StringRef> getSearchPaths(opt::InputArgList &args) {
   std::vector<StringRef> ret{args::getStrings(args, OPT_L)};
   if (!args.hasArg(OPT_Z)) {
     ret.push_back("/usr/lib");
     ret.push_back("/usr/local/lib");
   }