[MC] Diagnose MCContext errors using LLVMContext handler

[ychen]

Summary

This happens before we reset the MCContext so that errors are propagated
to users. Without this, some errors are silently ignored even with a
correct error message.

[tejohnson]

lgtm

[rnk]

llvm/lib/CodeGen/MachineModuleInfo.cpp

172–173

This doesn't seem like a great user experience. Won't we get two errors, something like the following?

error: lds: unsupported initializer for address space
error: MC error

It seems worth adding an LLVMContext API to mark errors as having been reported another way if we don't have plans to unify MCContext / LLVMContext error reporting in the short term.

[MaskRay]

This happens before we reset the MCContext so that errors are propagated to users.

reset -> because?

Perhaps also document the error code change.

[ychen]

Thanks for the comment. I didn't find a satisfying workaround for this issue so I went ahead going the way @rnk suggested and wrote the better fix. D97449

[ychen]

Committed D97449 instead.

llvm/lib/CodeGen/MachineModuleInfo.cpp

 }
 
 void MachineModuleInfo::finalize() {
   Personalities.clear();
 
   delete AddrLabelSymbols;
   AddrLabelSymbols = nullptr;
 
+  if (Context.hadError())
+    TheModule->getContext().emitError("MC error");
+
   Context.reset();
   // We don't clear the ExternalContext.
 
   delete ObjFileMMI;
   ObjFileMMI = nullptr;
 }
 
 MachineModuleInfo::MachineModuleInfo(MachineModuleInfo &&MMI)

llvm/test/CodeGen/AMDGPU/lds-initializer.ll

-; RUN: llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
-; RUN: llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
 
 ; CHECK: lds: unsupported initializer for address space
 
 @lds = addrspace(3) global [8 x i32] [i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8]
 
 define amdgpu_kernel void @load_init_lds_global(i32 addrspace(1)* %out, i1 %p) {
  %gep = getelementptr [8 x i32], [8 x i32] addrspace(3)* @lds, i32 0, i32 10
   %ld = load i32, i32 addrspace(3)* %gep
   store i32 %ld, i32 addrspace(1)* %out
   ret void
 }

llvm/test/CodeGen/AMDGPU/lds-zero-initializer.ll

-; RUN: llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
-; RUN: llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
 
 ; CHECK: lds: unsupported initializer for address space
 
 @lds = addrspace(3) global [256 x i32] zeroinitializer
 
 define amdgpu_kernel void @load_zeroinit_lds_global(i32 addrspace(1)* %out, i1 %p) {
  %gep = getelementptr [256 x i32], [256 x i32] addrspace(3)* @lds, i32 0, i32 10
   %ld = load i32, i32 addrspace(3)* %gep
   store i32 %ld, i32 addrspace(1)* %out
   ret void
 }

llvm/test/CodeGen/XCore/section-name.ll

-; RUN: llc < %s -march=xcore -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc < %s -march=xcore -o /dev/null 2>&1 | FileCheck %s
 
 @bar = internal global i32 zeroinitializer
 
 define void @".dp.bss"() {
   ret void
 }
 
 ; CHECK: <unknown>:0: error: invalid symbol redefinition