Restore correct x86_64 EH encodings in kernel code model

[lliu0]

Summary

Fixes PR37524.

The exception handling encodings for x86_64 in kernel code model has been changed with r309884. Restore it to correct ones. These encodings include PersonalityEncoding, LSDAEncoding and TTypeEncoding.

[JDevlieghere]

• I guess a possible alternative would have been to set LargeCodeModel to true for kernel case? Regardless, I'd prefer being explicit to prevent confusion.
• I'm slightly worried about the default value being CodeModel::Small in case other parts in MCObjectFileInfo start relying on this, but it's definitely the most sensible.

So all things considered this LGTM.

[rnk]

Rafael's commit message was still correct, this shouldn't be part of MCObjectFileInfo, it should be in TargetLoweringObjectFile, which is only used by CodeGen. Give me a minute to try to untangle that.

[rnk]

If we move some of this logic back up into CodeGen, that removes the need to pass the full code model to the assembler. I implemented this in D50533. Please take a look. You should be able to rebase your change to the x86_64 EH encodings on that, removing the need to thread the code model to MC.

[lliu0]

Rebased after rL339397.

[rnk]

Code looks good, but we should strengthen the test case.

test/CodeGen/X86/code-model-kernel.ll

3 ↗

(On Diff #160049)

Please check all the relevant .cfi directives and the .byte that comes before this comment. For example, the number after .cfi_personalty should change as a result of this patch.

[lliu0]

Update test case.

[rnk]

Looks good, thanks!

[hvdijk]

llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

135

This looks like it's the wrong way around compared to the rest. I'm also not sure why the medium code model is treated like small in the PIC case, but like large in the non-PIC case, shouldn't it be the same for both?

[hvdijk]

llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

135

Proposed to swap sdata4 and sdata8 in D102132. The different handling of the medium model between the PIC and non-PIC cases actually looks like it might be correct after all: in the PIC case, we do not store the typeinfo address directly.

llvm/trunk/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

 //                                  ELF
 //===----------------------------------------------------------------------===//
 
 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
                                              const TargetMachine &TgtM) {
   TargetLoweringObjectFile::Initialize(Ctx, TgtM);
   TM = &TgtM;
 
-  bool Large = TgtM.getCodeModel() == CodeModel::Large;
+  CodeModel::Model CM = TgtM.getCodeModel();
 
   switch (TgtM.getTargetTriple().getArch()) {
   case Triple::arm:
   case Triple::armeb:
   case Triple::thumb:
   case Triple::thumbeb:
     if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
       break;
LSDAEncoding = isPositionIndependent()
                        : dwarf::DW_EH_PE_absptr;
     TTypeEncoding = isPositionIndependent()
                         ? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
                               dwarf::DW_EH_PE_sdata4
                         : dwarf::DW_EH_PE_absptr;
     break;
   case Triple::x86_64:
     if (isPositionIndependent()) {
-      PersonalityEncoding =
-          dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
-          (Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
+      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
+        ((CM == CodeModel::Small || CM == CodeModel::Medium)
+         ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
       LSDAEncoding = dwarf::DW_EH_PE_pcrel |
-                     (Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
+        (CM == CodeModel::Small
+         ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
-                      (Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
+        ((CM == CodeModel::Small || CM == CodeModel::Medium)
+         ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
     } else {
       PersonalityEncoding =
-          Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
-      LSDAEncoding = Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
-      TTypeEncoding = Large ? dwarf::DW_EH_PE_absptr : dwarf::DW_EH_PE_udata4;
+        (CM == CodeModel::Small || CM == CodeModel::Medium)
+        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
+      LSDAEncoding = (CM == CodeModel::Small)
+        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
+      TTypeEncoding = (CM == CodeModel::Small)
+        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
     }
     break;
   case Triple::hexagon:
     PersonalityEncoding = dwarf::DW_EH_PE_absptr;
     LSDAEncoding = dwarf::DW_EH_PE_absptr;
     TTypeEncoding = dwarf::DW_EH_PE_absptr;
     if (isPositionIndependent()) {
       PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;

llvm/trunk/test/CodeGen/X86/code-model-kernel.ll

+; RUN: llc -mtriple=x86_64-pc-linux-gnu -code-model=kernel %s -o - | FileCheck %s
+; CHECK-LABEL: main
+; CHECK: .cfi_startproc
+; CHECK: .cfi_personality 0, __gxx_personality_v0
+; CHECK: .cfi_lsda 0, [[EXCEPTION_LABEL:.L[^ ]*]]
+; CHECK: [[EXCEPTION_LABEL]]:
+; CHECK: .byte  0                       # @TType Encoding = absptr
+; CHECK: .quad  _ZTIi
+
+@_ZTIi = external constant i8*
+
+; Function Attrs: noinline norecurse optnone uwtable
+define i32 @main() #0 personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+  %1 = alloca i32, align 4
+  %2 = alloca i8*
+  %3 = alloca i32
+  %4 = alloca i32, align 4
+  store i32 0, i32* %1, align 4
+  %5 = call i8* @__cxa_allocate_exception(i64 4) #2
+  %6 = bitcast i8* %5 to i32*
+  store i32 20, i32* %6, align 16
+  invoke void @__cxa_throw(i8* %5, i8* bitcast (i8** @_ZTIi to i8*), i8* null) #3
+          to label %26 unwind label %7
+
+; <label>:7:                                      ; preds = %0
+  %8 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @_ZTIi to i8*)
+  %9 = extractvalue { i8*, i32 } %8, 0
+  store i8* %9, i8** %2, align 8
+  %10 = extractvalue { i8*, i32 } %8, 1
+  store i32 %10, i32* %3, align 4
+  br label %11
+
+; <label>:11:                                     ; preds = %7
+  %12 = load i32, i32* %3, align 4
+  %13 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) #2
+  %14 = icmp eq i32 %12, %13
+  br i1 %14, label %15, label %21
+
+; <label>:15:                                     ; preds = %11
+  %16 = load i8*, i8** %2, align 8
+  %17 = call i8* @__cxa_begin_catch(i8* %16) #2
+  %18 = bitcast i8* %17 to i32*
+  %19 = load i32, i32* %18, align 4
+  store i32 %19, i32* %4, align 4
+  call void @__cxa_end_catch() #2
+  br label %20
+
+; <label>:20:                                     ; preds = %15
+  ret i32 0
+
+; <label>:21:                                     ; preds = %11
+  %22 = load i8*, i8** %2, align 8
+  %23 = load i32, i32* %3, align 4
+  %24 = insertvalue { i8*, i32 } undef, i8* %22, 0
+  %25 = insertvalue { i8*, i32 } %24, i32 %23, 1
+  resume { i8*, i32 } %25
+
+; <label>:26:                                     ; preds = %0
+  unreachable
+}
+
+declare i8* @__cxa_allocate_exception(i64)
+
+declare void @__cxa_throw(i8*, i8*, i8*)
+
+declare i32 @__gxx_personality_v0(...)
+
+; Function Attrs: nounwind readnone
+declare i32 @llvm.eh.typeid.for(i8*) #1
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+attributes #0 = { noinline norecurse optnone uwtable }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+attributes #3 = { noreturn }