[Autolink Extract] Keep a set of linker flags instead of vector

Otherwise we can duplicate linker flags across input binaries, which can result in very large linkerr invocation commands.

Resolves #58380

Author: artemcm

lib/DriverTool/autolink_extract_main.cpp

@@ -18,6 +18,7 @@
 
 #include <string>
 #include <vector>
+#include <set>
 
 #include "swift/AST/DiagnosticsFrontend.h"
 #include "swift/Frontend/Frontend.h"
@@ -38,6 +39,23 @@
 using namespace swift;
 using namespace llvm::opt;
 
+// Identifiers hash just like pointers.
+template<> struct llvm::DenseMapInfo<std::string> {
+  static std::string getEmptyKey() {
+    return swift::Identifier::getEmptyKey().str().str();
+  }
+  static std::string getTombstoneKey() {
+    return swift::Identifier::getTombstoneKey().str().str();
+  }
+  static unsigned getHashValue(std::string Val) {
+    std::hash<std::string> Hasher;
+    return Hasher(Val);
+  }
+  static bool isEqual(std::string LHS, std::string RHS) {
+    return LHS == RHS;
+  }
+};
+
 class AutolinkExtractInvocation {
 private:
   std::string MainExecutablePath;
@@ -112,7 +130,7 @@ class AutolinkExtractInvocation {
 /// Return 'true' if there was an error, and 'false' otherwise.
 static bool
 extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
-                                 std::vector<std::string> &LinkerFlags,
+                                 llvm::SetVector<std::string> &LinkerFlags,
                                  CompilerInstance &Instance) {
   // Search for the section we hold autolink entries in
   for (auto &Section : ObjectFile->sections()) {
@@ -141,7 +159,7 @@ extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
       SectionData->split(SplitFlags, llvm::StringRef("\0", 1), -1,
                          /*KeepEmpty=*/false);
       for (const auto &Flag : SplitFlags)
-        LinkerFlags.push_back(Flag.str());
+        LinkerFlags.insert(Flag.str());
     }
   }
   return false;
@@ -152,7 +170,7 @@ extractLinkerFlagsFromObjectFile(const llvm::object::ObjectFile *ObjectFile,
 /// 'true' if there was an error, and 'false' otherwise.
 static bool
 extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
-                                 std::vector<std::string> &LinkerFlags,
+                                 llvm::SetVector<std::string> &LinkerFlags,
                                  CompilerInstance &Instance) {
   // Search for the data segment we hold autolink entries in
   for (const llvm::object::WasmSegment &Segment : ObjectFile->dataSegments()) {
@@ -165,7 +183,7 @@ extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
       SegmentData.split(SplitFlags, llvm::StringRef("\0", 1), -1,
                         /*KeepEmpty=*/false);
       for (const auto &Flag : SplitFlags)
-        LinkerFlags.push_back(Flag.str());
+        LinkerFlags.insert(Flag.str());
     }
   }
   return false;
@@ -178,7 +196,7 @@ extractLinkerFlagsFromObjectFile(const llvm::object::WasmObjectFile *ObjectFile,
 static bool extractLinkerFlags(const llvm::object::Binary *Bin,
                                CompilerInstance &Instance,
                                StringRef BinaryFileName,
-                               std::vector<std::string> &LinkerFlags) {
+                               llvm::SetVector<std::string> &LinkerFlags) {
   if (auto *ObjectFile = llvm::dyn_cast<llvm::object::ELFObjectFileBase>(Bin)) {
     return extractLinkerFlagsFromObjectFile(ObjectFile, LinkerFlags, Instance);
   } else if (auto *ObjectFile =
@@ -227,7 +245,7 @@ int autolink_extract_main(ArrayRef<const char *> Args, const char *Argv0,
     return 1;
   }
 
-  std::vector<std::string> LinkerFlags;
+  llvm::SetVector<std::string> LinkerFlags;
 
   // Extract the linker flags from the objects.
   for (const auto &BinaryFileName : Invocation.getInputFilenames()) {

test/AutolinkExtract/import.swift

@@ -1,10 +1,16 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swiftc_driver -emit-module -emit-module-path %t/empty.swiftmodule -module-name empty -module-link-name empty %S/empty.swift
 // RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental.o
-// RUN: %target-swift-autolink-extract %t/import_experimental.o -o - | %FileCheck --check-prefix CHECK-%target-object-format %s
+// RUN: %target-swiftc_driver -c %s -I %t -o %t/import_experimental_again.o
+// RUN: %target-swift-autolink-extract %t/import_experimental.o %t/import_experimental_again.o -o - | %FileCheck --check-prefix CHECK-%target-object-format %s
+
+// RUN: %target-swift-autolink-extract %t/import_experimental.o %t/import_experimental_again.o -o - | %FileCheck --check-prefix UNIQUE %s
 
 // REQUIRES: autolink-extract
 
+// UNIQUE-COUNT-1: -lswiftCore
+// UNIQUE-COUNT-1: -lempty
+
 // CHECK-elf-DAG: -lswiftCore
 // CHECK-elf-DAG: -lempty