Automerge: LowerTypeTests: Set small code model on imported globals.

This is either a vtable (in .data.rel.ro) or a jump table (in .text).
Either way it's expected to be in the low 2 GiB, so set the small
code model.

Reviewers: fmayer

Reviewed By: fmayer

Pull Request: llvm/llvm-project#141324

Author: pcc

llvm/lib/Transforms/IPO/LowerTypeTests.cpp

@@ -1019,8 +1019,22 @@ LowerTypeTestsModule::importTypeId(StringRef TypeId) {
     return C;
   };
 
-  if (TIL.TheKind != TypeTestResolution::Unsat)
-    TIL.OffsetedGlobal = ImportGlobal("global_addr");
+  if (TIL.TheKind != TypeTestResolution::Unsat) {
+    auto *GV = ImportGlobal("global_addr");
+    // This is either a vtable (in .data.rel.ro) or a jump table (in .text).
+    // Either way it's expected to be in the low 2 GiB, so set the small code
+    // model.
+    //
+    // For .data.rel.ro, we currently place all such sections in the low 2 GiB
+    // [1], and for .text the sections are expected to be in the low 2 GiB under
+    // the small and medium code models [2] and this pass only supports those
+    // code models (e.g. jump tables use jmp instead of movabs/jmp).
+    //
+    // [1]https://github.com/llvm/llvm-project/pull/137742
+    // [2]https://maskray.me/blog/2023-05-14-relocation-overflow-and-code-models
+    GV->setCodeModel(CodeModel::Small);
+    TIL.OffsetedGlobal = GV;
+  }
 
   if (TIL.TheKind == TypeTestResolution::ByteArray ||
       TIL.TheKind == TypeTestResolution::Inline ||

llvm/test/Transforms/LowerTypeTests/import.ll

@@ -6,29 +6,29 @@ target datalayout = "e-p:64:64"
 
 declare i1 @llvm.type.test(ptr %ptr, metadata %bitset) nounwind readnone
 
-; CHECK-DAG: @__typeid_single_global_addr = external hidden global [0 x i8]
-; CHECK-DAG: @__typeid_inline6_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_single_global_addr = external hidden global [0 x i8], code_model "small"
+; CHECK-DAG: @__typeid_inline6_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_inline6_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_inline6_size_m1 = external hidden global [0 x i8], !absolute_symbol !1
 ; X86-DAG: @__typeid_inline6_inline_bits = external hidden global [0 x i8], !absolute_symbol !2
-; CHECK-DAG: @__typeid_inline5_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_inline5_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_inline5_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_inline5_size_m1 = external hidden global [0 x i8], !absolute_symbol !3
 ; X86-DAG: @__typeid_inline5_inline_bits = external hidden global [0 x i8], !absolute_symbol !4
-; CHECK-DAG: @__typeid_bytearray32_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_bytearray32_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_bytearray32_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_bytearray32_size_m1 = external hidden global [0 x i8], !absolute_symbol !4
 ; CHECK-DAG: @__typeid_bytearray32_byte_array = external hidden global [0 x i8]
 ; X86-DAG: @__typeid_bytearray32_bit_mask = external hidden global [0 x i8], !absolute_symbol !0
-; CHECK-DAG: @__typeid_bytearray7_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_bytearray7_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_bytearray7_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_bytearray7_size_m1 = external hidden global [0 x i8], !absolute_symbol !5
 ; CHECK-DAG: @__typeid_bytearray7_byte_array = external hidden global [0 x i8]
 ; X86-DAG: @__typeid_bytearray7_bit_mask = external hidden global [0 x i8], !absolute_symbol !0
-; CHECK-DAG: @__typeid_allones32_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_allones32_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_allones32_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_allones32_size_m1 = external hidden global [0 x i8], !absolute_symbol !4
-; CHECK-DAG: @__typeid_allones7_global_addr = external hidden global [0 x i8]
+; CHECK-DAG: @__typeid_allones7_global_addr = external hidden global [0 x i8], code_model "small"
 ; X86-DAG: @__typeid_allones7_align = external hidden global [0 x i8], !absolute_symbol !0
 ; X86-DAG: @__typeid_allones7_size_m1 = external hidden global [0 x i8], !absolute_symbol !5