asm keyword is generating wrong output C code when --cc:tcc

[rockcavera]

asm keyword is generating wrong output C code when --cc:tcc. The generated C code should be the same for --cc:gcc|clang. Look here

Example Nim Code

var
  eax, ebx, ecx, edx: uint32

eax = 1'u32

proc cpuid() =
  when defined(gcc) or defined(clang) or defined(tcc):
    asm """
      cpuid
      : "=a"(`eax`), "=b"(`ebx`), "=c"(`ecx`), "=d"(`edx`)
      : "0"(`eax`), "2"(`ecx`)
    """

proc popcntSupported(): bool =
  if ((ecx shr 22) and 1) == 1:
    result = true

cpuid()

echo "POPCNT supported? ", popcntSupported()

Output C code with --cc:tcc

N_LIB_PRIVATE N_NIMCALL(void, cpuid__zK4UNzi7M71mrmjIVqBcSw)(void) {	__asm{
      cpuid
      : "=a"(eax__wMLBI2U9chfYkOYd1K7nHVQ), "=b"(ebx__RNTC0gK57Uh1qU2JpDrt7A), "=c"(ecx__lNgxrjyiCIFlkB4Q6yvIfg), "=d"(edx__dqO2xuySrb2WMskvBE6j1A)
      : "0"(eax__wMLBI2U9chfYkOYd1K7nHVQ), "2"(ecx__lNgxrjyiCIFlkB4Q6yvIfg)
    

}
}

Expected Output C code with --cc:tcc

N_LIB_PRIVATE N_NIMCALL(void, cpuid__zK4UNzi7M71mrmjIVqBcSw)(void) {	asm("      cpuid\n"
      : "=a"(eax__wMLBI2U9chfYkOYd1K7nHVQ), "=b"(ebx__RNTC0gK57Uh1qU2JpDrt7A), "=c"(ecx__lNgxrjyiCIFlkB4Q6yvIfg), "=d"(edx__dqO2xuySrb2WMskvBE6j1A)
      : "0"(eax__wMLBI2U9chfYkOYd1K7nHVQ), "2"(ecx__lNgxrjyiCIFlkB4Q6yvIfg)
);
}

Possible Solution

• Use same output C code for --cc:gcc|tcc

Additional Information

• The tcc document suggests using keyword "__ asm __", but I was able to compile with tcc using "asm" and "__asm". The C code generated by Nim is using "{...}", must be used "(...)".
• Another error is "cpuid" outside the double quotes in the generated C code.

$ nim -v
Nim Compiler Version 1.1.1 [Windows: amd64]
Compiled at 2019-12-25
Copyright (c) 2006-2019 by Andreas Rumpf

git hash: 649bf326bfc6b4eb983403d850b1dcfc0cc854ae
active boot switches: -d:release

[juancarlospaco]

Does asm even work for TinyC ? 🤔

[Clyybber]

@juancarlospaco Yes, see Additional Information above :)

[Araq]

easy to fix... edit compiler/extccomp.nim