[AVR] Fix a bug in AsmPrinter when printing inline-asm operands

[benshi001]

Summary

fixes https://github.com/llvm/llvm-project/issues/58878

[benshi001]

llvm/lib/Target/AVR/AVRAsmPrinter.cpp

132

It would be better to return true and the upper llvm assembler handle the error.

For example, with the following c code

void fooa(void);
int foob(void) {
        int result;
        fooa();
        __asm (";; %C0" : "=d" (result));
        fooa();
        return result;
}

Built it with clang, the clang will give detailed errors.

benshi@BJSW-T026:~/llvm-project/build$ ./bin/clang a.c -O3 -Wall --target=avr -mmcu=atmega328 -S
a.c:6:9: error: invalid operand in inline asm: ';; ${0:C}'
        __asm (";; %C0" : "=d" (result));
               ^
1 error generated.

llvm/lib/Target/AVR/AVRAsmPrinter.cpp

if (ExtraCode[0] >= 'A' && ExtraCode[0] <= 'Z') {
       const AVRSubtarget &STI = MF->getSubtarget<AVRSubtarget>();
       const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
 
       const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(Reg);
       unsigned BytesPerReg = TRI.getRegSizeInBits(*RC) / 8;
       assert(BytesPerReg <= 2 && "Only 8 and 16 bit regs are supported.");
 
       unsigned RegIdx = ByteNumber / BytesPerReg;
-      assert(RegIdx < NumOpRegs && "Multibyte index out of range.");
-
+      if (RegIdx >= NumOpRegs)
+        return true;
       Reg = MI->getOperand(OpNum + RegIdx).getReg();
 
       if (BytesPerReg == 2) {
         Reg = TRI.getSubReg(Reg, ByteNumber % BytesPerReg ? AVR::sub_hi
                                                           : AVR::sub_lo);
       }
 
       O << AVRInstPrinter::getPrettyRegisterName(Reg, MRI);

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* elementtype(i32) %i.addr)
 
   ret void
 }
 
+define void @foo1() {
+  ; CHECK: error: invalid operand in inline asm: ';; ${0:C}'
+  call i16 asm sideeffect ";; ${0:C}", "=d"()
+  ret void
+}