Do not set alignment and don't set disableAddressSanitizer on @llvm.used and @llvm.compiler.used (swiftlang#34970)

* Do not set alignment and don't set disableAddressSanitizer on @llvm.used and @llvm.compiler.used

* Update tests

Author: kubamracek

lib/IRGen/GenDecl.cpp

@@ -570,8 +570,14 @@ emitGlobalList(IRGenModule &IGM, ArrayRef<llvm::WeakTrackingVH> handles,
   auto var = new llvm::GlobalVariable(IGM.Module, varTy, isConstant, linkage,
                                       init, name);
   var->setSection(section);
-  var->setAlignment(llvm::MaybeAlign(alignment.getValue()));
-  disableAddressSanitizer(IGM, var);
+
+  // Do not set alignment and don't set disableAddressSanitizer on @llvm.used
+  // and @llvm.compiler.used. Doing so confuses LTO (merging) and they're not
+  // going to end up as real global symbols in the binary anyways.
+  if (name != "llvm.used" && name != "llvm.compiler.used") {
+    var->setAlignment(llvm::MaybeAlign(alignment.getValue()));
+    disableAddressSanitizer(IGM, var);
+  }
 
   // Mark the variable as used if doesn't have external linkage.
   // (Note that we'd specifically like to not put @llvm.used in itself.)

test/IRGen/autolink-coff-x86.swift

@@ -11,7 +11,7 @@ import module
 #endif
 
 // CHECK-GNU-IR: @_swift1_autolink_entries = private constant [9 x i8] c"-lmodule\00", section ".swift1_autolink_entries", align 8
-// CHECK-GNU-IR: @llvm.used = appending global [{{.*}} x i8*] [{{.*}}i8* getelementptr inbounds ([9 x i8], [9 x i8]* @_swift1_autolink_entries, i32 0, i32 0){{.*}}], section "llvm.metadata", align 8
+// CHECK-GNU-IR: @llvm.used = appending global [{{.*}} x i8*] [{{.*}}i8* getelementptr inbounds ([9 x i8], [9 x i8]* @_swift1_autolink_entries, i32 0, i32 0){{.*}}], section "llvm.metadata"
 
 // CHECK-GNU-ASM: .section	.swift1_autolink_entries{{.*}}
 // CHECK-GNU-ASM: .asciz  "-lmodule"

test/IRGen/autolink_elf.swift

@@ -10,5 +10,5 @@ import Empty
 // as used.
 
 // CHECK-DAG: @_swift1_autolink_entries = private constant [26 x i8] c"-lswiftEmpty\00-lanotherLib\00", section ".swift1_autolink_entries", align 8
-// CHECK-DAG: @llvm.used = appending global [{{.*}} x i8*] [{{.*}}i8* getelementptr inbounds ([26 x i8], [26 x i8]* @_swift1_autolink_entries, i32 0, i32 0){{.*}}], section "llvm.metadata", align 8
+// CHECK-DAG: @llvm.used = appending global [{{.*}} x i8*] [{{.*}}i8* getelementptr inbounds ([26 x i8], [26 x i8]* @_swift1_autolink_entries, i32 0, i32 0){{.*}}], section "llvm.metadata"
 

test/IRGen/unused.sil

@@ -55,8 +55,8 @@ bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>
 // CHECK-macho: @"\01l_entry_point" = private constant { i32 } { i32 trunc (i64 sub (i64 ptrtoint (i32 (i32, i8**)* @main to i64), i64 ptrtoint ({ i32 }* @"\01l_entry_point" to i64)) to i32) }, section "__TEXT, __swift5_entry, regular, no_dead_strip", align 4
 // CHECK-elf: @"\01l_entry_point" = private constant { i32 } { i32 trunc (i64 sub (i64 ptrtoint (i32 (i32, i8**)* @main to i64), i64 ptrtoint ({ i32 }* @"\01l_entry_point" to i64)) to i32) }, section "swift5_entry", align 4
 
-// CHECK-macho: @llvm.used = appending global [4 x i8*] [i8* bitcast (void ()* @frieda to i8*), i8* bitcast (i32 (i32, i8**)* @main to i8*), i8* bitcast ({ i32 }* @"\01l_entry_point" to i8*), i8* bitcast (i16* @__swift_reflection_version to i8*)], section "llvm.metadata", align 8
-// CHECK-elf: @llvm.used = appending global [5 x i8*] [i8* bitcast (void ()* @frieda to i8*), i8* bitcast (i32 (i32, i8**)* @main to i8*), i8* bitcast ({ i32 }* @"\01l_entry_point" to i8*), i8* bitcast (i16* @__swift_reflection_version to i8*), i8* getelementptr inbounds ([{{[0-9]+}} x i8], [{{[0-9]+}} x i8]* @_swift1_autolink_entries, i32 0, i32 0)], section "llvm.metadata", align 8
+// CHECK-macho: @llvm.used = appending global [4 x i8*] [i8* bitcast (void ()* @frieda to i8*), i8* bitcast (i32 (i32, i8**)* @main to i8*), i8* bitcast ({ i32 }* @"\01l_entry_point" to i8*), i8* bitcast (i16* @__swift_reflection_version to i8*)], section "llvm.metadata"
+// CHECK-elf: @llvm.used = appending global [5 x i8*] [i8* bitcast (void ()* @frieda to i8*), i8* bitcast (i32 (i32, i8**)* @main to i8*), i8* bitcast ({ i32 }* @"\01l_entry_point" to i8*), i8* bitcast (i16* @__swift_reflection_version to i8*), i8* getelementptr inbounds ([{{[0-9]+}} x i8], [{{[0-9]+}} x i8]* @_swift1_autolink_entries, i32 0, i32 0)], section "llvm.metadata"
 
 // CHECK: define linkonce_odr hidden swiftcc void @qux()
 // CHECK: define hidden swiftcc void @fred()