[GlobalISel][IRTranslator] Add special case support for ~memory inline asm clobber

[aemerson]

Summary

This is a one off special case, since actually implementing full inline asm support will be much more involved. This special case lets us compile a lot more code as a common simple case.

[arsenm]

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

1567

Missing } in comment

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
   }
   }
   return false;
 }
 
 bool IRTranslator::translateInlineAsm(const CallInst &CI,
                                       MachineIRBuilder &MIRBuilder) {
   const InlineAsm &IA = cast<InlineAsm>(*CI.getCalledValue());
-  if (!IA.getConstraintString().empty())
+  StringRef ConstraintStr = IA.getConstraintString();
+
+  bool HasOnlyMemoryClobber = false;
+  if (!ConstraintStr.empty()) {
+    // Until we have full inline assembly support, we just try to handle the
+    // very simple case of just "~{memory}" to avoid falling back so often.
+    if (ConstraintStr != "~{memory}")
       return false;
+    HasOnlyMemoryClobber = true;
+  }
 
   unsigned ExtraInfo = 0;
   if (IA.hasSideEffects())
     ExtraInfo |= InlineAsm::Extra_HasSideEffects;
   if (IA.getDialect() == InlineAsm::AD_Intel)
     ExtraInfo |= InlineAsm::Extra_AsmDialect;
 
-  MIRBuilder.buildInstr(TargetOpcode::INLINEASM)
+  // HACK: special casing for ~memory.
+  if (HasOnlyMemoryClobber)
+    ExtraInfo |= (InlineAsm::Extra_MayLoad | InlineAsm::Extra_MayStore);
+
+  auto Inst = MIRBuilder.buildInstr(TargetOpcode::INLINEASM)
                   .addExternalSymbol(IA.getAsmString().c_str())
                   .addImm(ExtraInfo);
+  if (const MDNode *SrcLoc = CI.getMetadata("srcloc"))
+    Inst.addMetadata(SrcLoc);
 
   return true;
 }
 
 bool IRTranslator::translateCallSite(const ImmutableCallSite &CS,
                                      MachineIRBuilder &MIRBuilder) {
   const Instruction &I = *CS.getInstruction();
   ArrayRef<Register> Res = getOrCreateVRegs(I);

llvm/test/CodeGen/AArch64/GlobalISel/translate-inline-asm.ll

+; RUN: llc -mtriple=aarch64-darwin-ios13 -O0 -global-isel -stop-after=irtranslator -o - %s | FileCheck %s
+
+; The update_mir_test_checks script doesn't seem to handle INLINE_ASM well. Write this manually.
+
+define void @asm_simple_memory_clobber() {
+  ; CHECK-LABEL: name: asm_simple_memory_clobber
+  ; CHECK: INLINEASM &"", 25
+  ; CHECK:  INLINEASM &"", 1
+  call void asm sideeffect "", "~{memory}"(), !srcloc !0
+  call void asm sideeffect "", ""(), !srcloc !0
+  ret void
+}
+
+!0 = !{i32 70}