[asm] Remove explicit branch for modifier 'l'

[thakis]

Summary

No intended behavior change.

EmitGCCInlineAsmStr() used to explicitly check for modifier 'l'
after handling block address and machine basic block operands.
This prevented passing a MachineOperand with 'l' modifier to
PrintAsmMemoryOperand(). Conceptually that seems kind of nice,
but in practice the overrides of PrintAsmMemoryOperand() in all (*)
AsmPrinter subclasses already reject modifiers they don't know about,
and none of them don't know about 'l'. So removing this doesn't have
a behavior difference, is less code, and it makes EmitGCCInlineAsmStr()
and EmitMSInlineAsmStr() more similar, to prepare for merging them later.

(Why not _add_ the branch to EmitMSInlineAsmStr() instead? Because that
always works with X86AsmPrinter I think, and
X86AsmPrinter::PrintAsmMemoryOperand() very decisively rejects the 'l'
modifier, so it's hard to motivate adding that branch.)

*: The one exception was AVRAsmPrinter, which had an llvm_unreachable instead
of returning true. So this commit changes that, so that the AVR target keeps
emitting an error instead of crashing when passing a mem operand with a :l
modifier to it. All the other targets already don't crash on this.

[thakis]

llvm/test/CodeGen/AVR/inline-asm/inline-asm-invalid.ll

7

IR of this form can be emitted by clang for e.g. this (nonsensical) code:

void f(int i) { asm volatile("jmpl %0"::"m"(i):); }

[hans]

lgtm

llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

case '$': {
           if (MI->getOperand(OpNo).isBlockAddress()) {
             const BlockAddress *BA = MI->getOperand(OpNo).getBlockAddress();
             MCSymbol *Sym = AP->GetBlockAddressSymbol(BA);
             Sym->print(OS, AP->MAI);
             MMI->getContext().registerInlineAsmLabel(Sym);
           } else if (MI->getOperand(OpNo).isMBB()) {
             const MCSymbol *Sym = MI->getOperand(OpNo).getMBB()->getSymbol();
             Sym->print(OS, AP->MAI);
-          } else if (Modifier[0] == 'l') {
-            Error = true;
           } else if (InlineAsm::isMemKind(OpFlags)) {
             Error = AP->PrintAsmMemoryOperand(
                 MI, OpNo, Modifier[0] ? Modifier : nullptr, OS);
           } else {
             Error = AP->PrintAsmOperand(MI, OpNo,
                                         Modifier[0] ? Modifier : nullptr, OS);
           }
         }

llvm/lib/Target/AVR/AVRAsmPrinter.cpp

if (Error)
     printOperand(MI, OpNum, O);
 
   return false;
 }
 
 bool AVRAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
                                           unsigned OpNum, const char *ExtraCode,
                                           raw_ostream &O) {
-  if (ExtraCode && ExtraCode[0]) {
-    llvm_unreachable("This branch is not implemented yet");
-  }
+  if (ExtraCode && ExtraCode[0])
+    return true; // Unknown modifier
 
   const MachineOperand &MO = MI->getOperand(OpNum);
   (void)MO;
   assert(MO.isReg() && "Unexpected inline asm memory operand");
 
   // TODO: We should be able to look up the alternative name for
   // the register if it's given.
   // TableGen doesn't expose a way of getting retrieving names

llvm/test/CodeGen/AVR/inline-asm/inline-asm-invalid.ll

+; RUN: not llc < %s -march=avr -no-integrated-as 2>&1 | FileCheck %s
+
+define void @foo(i16 %a) {
+  ; CHECK: error: invalid operand in inline asm: 'jl ${0:l}'
+  %i.addr = alloca i32, align 4
+  call void asm sideeffect "jl ${0:l}", "*m"(i32* %i.addr)
+
+  ret void
+}
+