[lld-macho] Fix default LTO triple

[keith]

Summary

In the case you pass -object_path_lto without any IR files, the LTO
infrastructure attempts to derive the default triple and fails if none
is found. This sets the default triple to the one we've derived from
-platform_version / -arch.

Fixes https://github.com/llvm/llvm-project/issues/61031

[int3]

Huh, I'm surprised that setting -object_path_lto has a functional difference; I thought it was only to make debugging the intermediate object files easier. Did you figure out why?

Also, did you figure out why LLD-ELF doesn't seem to need to set DefaultTriple?

lld/test/MachO/lto-object-path.ll

5

how does compiling with llc different from compiling with opt?

[keith]

In D145268#4168067, @int3 wrote:

Huh, I'm surprised that setting -object_path_lto has a functional difference; I thought it was only to make debugging the intermediate object files easier. Did you figure out why?

Also, did you figure out why LLD-ELF doesn't seem to need to set DefaultTriple?

so the difference with elf is it just avoids this work all together, here's a patch with that option https://reviews.llvm.org/D145273 and the original commit for that logic https://github.com/llvm/llvm-project/commit/f3994e4dfa0214b2a09a0e327ba37e6b38bbcdb3

with this patch the object_path_lto file ends up getting created and is empty, so technically the other patch would be less work, although I doubt it's meaningful perf wise

lld/test/MachO/lto-object-path.ll

5

the difference is that we want an object file here and the opt calls are producing bitcode files

[int3]

lld/test/MachO/lto-object-path.ll

5

d'oh, of course :)

[keith]

https://reviews.llvm.org/D145273

lld/MachO/LTO.cpp

 static lto::Config createConfig() {
   lto::Config c;
   c.Options = initTargetOptionsFromCodeGenFlags();
   c.Options.EmitAddrsig = config->icfLevel == ICFLevel::safe;
   for (StringRef C : config->mllvmOpts)
     c.MllvmArgs.emplace_back(C.str());
   c.CodeModel = getCodeModelFromCMModel();
   c.CPU = getCPUStr();
+  c.DefaultTriple = getTargetTripleName(config->platformInfo.target);
   c.MAttrs = getMAttrs();
   c.DiagHandler = diagnosticHandler;
   c.PreCodeGenPassesHook = [](legacy::PassManager &pm) {
     pm.add(createObjCARCContractPass());
   };
 
   c.AlwaysEmitRegularLTOObj = !config->ltoObjPath.empty();
 

lld/test/MachO/lto-object-path.ll

 ; REQUIRES: x86
 ; UNSUPPORTED: system-windows
 
 ; RUN: rm -rf %t; mkdir %t
+; RUN: llc -filetype=obj %s -o %t/test-obj.o
 ; RUN: opt -thinlto-bc %s -o %t/test.o
 ; RUN: opt %s -o %t/test-nonthin.o
 
 ; RUN: %lld %t/test.o -o %t/test
 ; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes CHECK,NOOBJPATH
 
+; RUN: %lld %t/test-obj.o -o %t/test-obj -object_path_lto %t/lto-temps-obj
+; RUN: llvm-nm -pa %t/test-obj | FileCheck %s --check-prefixes CHECK,NOLTOPATH -DDIR=%t
+; RUN: llvm-otool -l %t/lto-temps-obj/0.x86_64.lto.o | FileCheck %s --check-prefixes=MINOS-DEFAULT
+
 ; RUN: ZERO_AR_DATE=0 %lld %t/test.o -o %t/test -object_path_lto %t/lto-temps
 ; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes CHECK,OBJPATH-DIR -DDIR=%t/lto-temps
 
 ;; Ensure object path is still used if the cache is used
 ; RUN: ZERO_AR_DATE=0 %lld %t/test.o -o %t/test -object_path_lto %t/lto-temps -prune_interval_lto 20 -cache_path_lto %t/cache --thinlto-cache-policy=cache_size_files=1:cache_size_bytes=10
 ; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes CHECK,OBJPATH-DIR -DDIR=%t/lto-temps
 ;; And that dsymutil can read the result
 ; RUN: dsymutil -f -o - %t/test | llvm-dwarfdump - | FileCheck %s --check-prefix=DSYM
 
 ;; Test that the object path hardlinks to the cache when possible
 ;; NB:
 ;; 1) Need to delete current object path contents or hardlink will fail.
 ;; 2) Note the cache policy is different from the test above (which is crafted
 ;;    to ensure that the cache is pruned immediately; we want the opposite here).
 ; RUN: rm -rf %t/lto-temps
 ; RUN: %lld %t/test.o -o %t/test -object_path_lto %t/lto-temps -prune_interval_lto 20 -cache_path_lto %t/cache --thinlto-cache-policy=cache_size_files=10:cache_size_bytes=10000
 ;; Get the link count.
 ; RUN: ls -l %t/lto-temps/1.x86_64.lto.o | tr -s ' ' | cut -f 2 -d ' ' | FileCheck %s --check-prefix=HARDLINK
 
 ;; check that the object path can be an existing file
 ; RUN: touch %t/lto-tmp.o
 ; RUN: ZERO_AR_DATE=0 %lld %t/test-nonthin.o -o %t/test -object_path_lto %t/lto-tmp.o
 ; RUN: llvm-nm -pa %t/test | FileCheck %s --check-prefixes CHECK,OBJPATH-FILE -DFILE=%t/lto-tmp.o
+; RUN: llvm-otool -l %t/lto-tmp.o | FileCheck %s --check-prefixes=MINOS
 
 
 ; CHECK:             0000000000000000                - 00 0000    SO /tmp/test.cpp
 ; NOOBJPATH-NEXT:    0000000000000000                - 03 0001   OSO /tmp/lto.tmp
+; NOLTOPATH-NEXT:    0000000000000000                - 03 0001   OSO [[DIR]]/test-obj.o
 ;; check that modTime is nonzero when `-object_path_lto` is provided
 ; OBJPATH-DIR-NEXT:  {{[0-9a-f]*[1-9a-f]+[0-9a-f]*}} - 03 0001   OSO [[DIR]]/1.x86_64.lto.o
 ; OBJPATH-FILE-NEXT: {{[0-9a-f]*[1-9a-f]+[0-9a-f]*}} - 03 0001   OSO [[FILE]]
 ; CHECK-NEXT:        {{[0-9a-f]+}}                   - 01 0000   FUN _main
 ; CHECK-NEXT:        0000000000000001                - 00 0000   FUN
 ; CHECK-NEXT:        0000000000000000                - 01 0000    SO
 ; CHECK-NEXT:        {{[0-9a-f]+}}                   T _main
 ; DSYM: DW_AT_name ("test.cpp")
 ; HARDLINK: 2
 
+; MINOS: 10.15
+; MINOS-DEFAULT: 11.0
+
 target triple = "x86_64-apple-macosx10.15.0"
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @main() #0 !dbg !4 {
   ret void
 }
 
 !llvm.module.flags = !{ !0, !1 }