[WebAssembly] Fix MIR printing of reference types (#113028)

When printing a memory operand in MIR, this line

https://github.com/llvm/llvm-project/blob/d37bc32a65651e647148236ffb9728ea2e77eac3/llvm/lib/CodeGen/MachineOperand.cpp#L1247
calls this
https://github.com/llvm/llvm-project/blob/d37bc32a65651e647148236ffb9728ea2e77eac3/llvm/include/llvm/Support/Alignment.h#L238
which assumes `Rhs` (the size in this case) is positive.

But Wasm reference types' size is set to 0:
https://github.com/llvm/llvm-project/blob/d37bc32a65651e647148236ffb9728ea2e77eac3/llvm/include/llvm/CodeGen/ValueTypes.td#L326-L328

`getSize() > 0` condition was added with the Wasm reference types
support in
46667a1,
and it looks it was removed in #84751. This revives the condition so
that Wasm reference types will not crash the MIR printer.

Author: aheejin

llvm/lib/CodeGen/MachineOperand.cpp

@@ -1244,7 +1244,8 @@ void MachineMemOperand::print(raw_ostream &OS, ModuleSlotTracker &MST,
   }
   MachineOperand::printOperandOffset(OS, getOffset());
   if (!getSize().hasValue() ||
-      getAlign() != getSize().getValue().getKnownMinValue())
+      (!getSize().isZero() &&
+       getAlign() != getSize().getValue().getKnownMinValue()))
     OS << ", align " << getAlign().value();
   if (getAlign() != getBaseAlign())
     OS << ", basealign " << getBaseAlign().value();

llvm/test/CodeGen/WebAssembly/externref-globalget.ll

@@ -1,4 +1,7 @@
 ; RUN: llc < %s --mtriple=wasm32-unknown-unknown -asm-verbose=false -mattr=+reference-types | FileCheck %s
+; Test for MIR printing of reference types in other address spaces. This should
+; not error out.
+; RUN: llc < %s --mtriple=wasm32-unknown-unknown -asm-verbose=false -mattr=+reference-types -print-after=finalize-isel | FileCheck %s
 
 %externref = type ptr addrspace(10) ;; addrspace 10 is nonintegral