[lipo] add -remove flag (#188275)

Add the -remove flag to llvm-lipo. This matches the existing Darwin lipo
tool:
```
% xcrun lipo 2>&1 | grep remove
error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/lipo: one of -create, -thin <arch_type>, -extract <arch_type>, -remove <arch_type>, -replace <arch_type> <file_name>, -verify_arch <arch_type> ... , -archs, -info, or -detailed_info must be specified
    -remove <arch_type> [-remove <arch_type> ...]
```
Assisted-by: claude-code

llvm/test/tools/llvm-lipo/remove.test

@@ -0,0 +1,39 @@
+# RUN: yaml2obj %p/Inputs/i386-x86_64-universal.yaml -o %t-universal.o
+
+# RUN: not llvm-lipo %t-universal.o -remove arm64_32 -output /dev/null 2>&1 | FileCheck --check-prefix=ARCH_NOT_IN_FILE %s
+# ARCH_NOT_IN_FILE: does not contain the specified architecture arm64_32 to remove
+
+# RUN: yaml2obj %p/Inputs/i386-slice.yaml -o %t-i386.o
+# RUN: not llvm-lipo %t-i386.o -remove i386 -output /dev/null 2>&1 | FileCheck --check-prefix=INPUT_NOT_A_FAT_FILE %s
+# INPUT_NOT_A_FAT_FILE: must be a fat file when the -remove option is specified
+
+# RUN: not llvm-lipo -remove FakeArch %t-universal.o -output /dev/null 2>&1 | FileCheck --check-prefix=INVALID_ARCH %s
+# INVALID_ARCH: Invalid architecture: FakeArch
+
+# RUN: yaml2obj %p/Inputs/i386-x86_64-armv7-arm64-universal.yaml -o %t-4arch.o
+# RUN: llvm-lipo -remove i386 %t-4arch.o -output %t-removed.o
+# RUN: llvm-lipo -info %t-removed.o | FileCheck --check-prefix=REMOVE_ONE %s
+# REMOVE_ONE: x86_64 armv7 arm64
+
+# RUN: llvm-lipo -remove i386 %t-universal.o -output %t-only-x86_64.o
+# RUN: llvm-lipo -thin x86_64 %t-universal.o -output %t-thinned-x86_64.o
+# RUN: yaml2obj %p/Inputs/x86_64-slice.yaml -o %t-x86_64.o
+# RUN: cmp %t-thinned-x86_64.o %t-x86_64.o
+
+# Multiple -remove flags
+# RUN: llvm-lipo -remove i386 -remove armv7 %t-4arch.o -output %t-removed-multi.o
+# RUN: llvm-lipo -info %t-removed-multi.o | FileCheck --check-prefix=REMOVE_MULTI %s
+# REMOVE_MULTI: x86_64 arm64
+
+# Multiple -remove flags removing all but one arch
+# RUN: llvm-lipo -remove i386 -remove x86_64 -remove armv7 %t-4arch.o -output %t-removed-three.o
+# RUN: llvm-lipo -info %t-removed-three.o | FileCheck --check-prefix=REMOVE_THREE %s
+# REMOVE_THREE: arm64
+
+# Error: one of multiple -remove arches not in file
+# RUN: not llvm-lipo -remove i386 -remove arm64_32 %t-4arch.o -output /dev/null 2>&1 | FileCheck --check-prefix=MULTI_ARCH_NOT_IN_FILE %s
+# MULTI_ARCH_NOT_IN_FILE: does not contain the specified architecture arm64_32 to remove
+
+# Error: removing all arches
+# RUN: not llvm-lipo -remove i386 -remove x86_64 %t-universal.o -output /dev/null 2>&1 | FileCheck --check-prefix=REMOVE_ALL %s
+# REMOVE_ALL: removing all architectures would result in an empty universal binary

llvm/tools/llvm-lipo/LipoOpts.td

@@ -44,6 +44,11 @@ def extract : Option<["-", "--"], "extract", KIND_SEPARATE>,
            HelpText<"Create a universal output file containing only the specified "
                     "arch_type from the fat input file. Requires -output option">;
 
+def remove : Option<["-", "--"], "remove", KIND_SEPARATE>,
+           Group<action_group>,
+           HelpText<"Remove the specified arch_type from the universal input "
+                    "file. Requires -output option">;
+
 def create : Option<["-", "--"], "create", KIND_FLAG>,
              Group<action_group>,
              HelpText<"Create a universal binary output file from the input "

llvm/tools/llvm-lipo/llvm-lipo.cpp

@@ -99,6 +99,7 @@ enum class LipoAction {
   VerifyArch,
   ThinArch,
   ExtractArch,
+  RemoveArch,
   CreateUniversal,
   ReplaceArch,
 };
@@ -112,6 +113,7 @@ struct Config {
   SmallVector<InputFile, 1> InputFiles;
   SmallVector<std::string, 1> VerifyArchList;
   SmallVector<InputFile, 1> ReplacementFiles;
+  SmallVector<std::string, 1> RemoveArchList;
   StringMap<const uint32_t> SegmentAlignments;
   std::string ArchType;
   std::string OutputFile;
@@ -229,14 +231,18 @@ static Config parseLipoOptions(ArrayRef<const char *> ArgsArr) {
   SmallVector<opt::Arg *, 1> ActionArgs(InputArgs.filtered(LIPO_action_group));
   if (ActionArgs.empty())
     reportError("at least one action should be specified");
-  // errors if multiple actions specified other than replace
-  // multiple replace flags may be specified, as long as they are not mixed with
-  // other action flags
+  // errors if multiple actions specified other than replace or remove
+  // multiple replace/remove flags may be specified, as long as they are not
+  // mixed with other action flags
   auto ReplacementArgsRange = InputArgs.filtered(LIPO_replace);
+  auto RemoveArgsRange = InputArgs.filtered(LIPO_remove);
   if (ActionArgs.size() > 1 &&
       ActionArgs.size() !=
           static_cast<size_t>(std::distance(ReplacementArgsRange.begin(),
-                                            ReplacementArgsRange.end()))) {
+                                            ReplacementArgsRange.end())) &&
+      ActionArgs.size() !=
+          static_cast<size_t>(
+              std::distance(RemoveArgsRange.begin(), RemoveArgsRange.end()))) {
     std::string Buf;
     raw_string_ostream OS(Buf);
     OS << "only one of the following actions can be specified:";
@@ -287,6 +293,19 @@ static Config parseLipoOptions(ArrayRef<const char *> ArgsArr) {
     C.ActionToPerform = LipoAction::ExtractArch;
     return C;
 
+  case LIPO_remove:
+    for (auto *Action : ActionArgs) {
+      std::string ArchType = Action->getValue();
+      validateArchitectureName(ArchType);
+      C.RemoveArchList.push_back(ArchType);
+    }
+    if (C.InputFiles.size() > 1)
+      reportError("remove expects a single input file");
+    if (C.OutputFile.empty())
+      reportError("remove expects a single output file");
+    C.ActionToPerform = LipoAction::RemoveArch;
+    return C;
+
   case LIPO_create:
     if (C.OutputFile.empty())
       reportError("create expects a single output file to be specified");
@@ -672,6 +691,52 @@ extractSlice(LLVMContext &LLVMCtx, ArrayRef<OwningBinary<Binary>> InputBinaries,
   exit(EXIT_SUCCESS);
 }
 
+[[noreturn]] static void
+removeSlice(LLVMContext &LLVMCtx, ArrayRef<OwningBinary<Binary>> InputBinaries,
+            const StringMap<const uint32_t> &Alignments,
+            ArrayRef<std::string> ArchTypes, StringRef OutputFileName) {
+  assert(!ArchTypes.empty() &&
+         "The architecture type list should be non-empty");
+  assert(InputBinaries.size() == 1 && "Incorrect number of input binaries");
+  assert(!OutputFileName.empty() && "Remove expects a single output file");
+
+  if (InputBinaries.front().getBinary()->isMachO()) {
+    reportError("input file " +
+                InputBinaries.front().getBinary()->getFileName() +
+                " must be a fat file when the -remove option is specified");
+  }
+
+  SmallVector<std::unique_ptr<SymbolicFile>, 2> ExtractedObjects;
+  SmallVector<std::unique_ptr<Archive>, 2> ExtractedArchives;
+  SmallVector<Slice, 2> Slices = buildSlices(
+      LLVMCtx, InputBinaries, Alignments, ExtractedObjects, ExtractedArchives);
+
+  SmallVector<StringRef, 1> NotFound;
+  for (StringRef ArchType : ArchTypes) {
+    size_t SizeBefore = Slices.size();
+    erase_if(Slices, [ArchType](const Slice &S) {
+      return ArchType == S.getArchString();
+    });
+    if (Slices.size() == SizeBefore)
+      NotFound.push_back(ArchType);
+  }
+
+  if (!NotFound.empty())
+    reportError("fat input file " +
+                InputBinaries.front().getBinary()->getFileName() +
+                " does not contain the specified architecture " + NotFound[0] +
+                " to remove");
+
+  if (Slices.empty())
+    reportError(
+        "removing all architectures would result in an empty universal binary");
+
+  llvm::stable_sort(Slices);
+  if (Error E = writeUniversalBinary(Slices, OutputFileName))
+    reportError(std::move(E));
+  exit(EXIT_SUCCESS);
+}
+
 static StringMap<Slice>
 buildReplacementSlices(ArrayRef<OwningBinary<Binary>> ReplacementBinaries,
                        const StringMap<const uint32_t> &Alignments) {
@@ -770,6 +835,10 @@ int llvm_lipo_main(int argc, char **argv, const llvm::ToolContext &) {
     extractSlice(LLVMCtx, InputBinaries, C.SegmentAlignments, C.ArchType,
                  C.OutputFile);
     break;
+  case LipoAction::RemoveArch:
+    removeSlice(LLVMCtx, InputBinaries, C.SegmentAlignments, C.RemoveArchList,
+                C.OutputFile);
+    break;
   case LipoAction::CreateUniversal:
     createUniversalBinary(
         LLVMCtx, InputBinaries, C.SegmentAlignments, C.OutputFile,