🐛 Duplicate qubit label/s created during synthesis

[TooMuchDakka]

Environment information

• OS: Windows 10 x64
• C++ Compiler: clang 17.0.3
• MQT-Core: 3.0.3
• MQT-Syrec: Commit #995f203

Description

During the synthesis of the following SyReC program, duplicate qubit labels are created when the local variable c of module add is inlined by the CallStatement in the main module due to the identifier of the local variable matching the identifier of the parameter c.

module add(inout a(2), in b(2))
 wire c(2)

 a += (b + c)

module main(inout a(2), in c(2))
 call add(a, c)

Expected behavior

The SyReC program should be synthesizable without errors.

How to Reproduce

1. Perform a build from source of mqt.syrec
2. Launch the syrec-editor python application and copy the SyReC circuit from the bug description into the code editor
3. Select either the cost or line aware synthesis radio button and then press the 'Build' button

[TooMuchDakka]

Two issues should be addressed by a potential bugfix:

• What data should be contained in the label of a qubit (identifier, associated module, etc.)? Since this label is also displayed in the GUI of the syrec-editor one might have to update how this label is visualized in both the circuit as well as simulation view (the label might also be used by the user to debug issues in the GUI).
• Should synthesis error only be reported on the standard output or should the synthesis interface be updated to return the found errors instead? Additionally, not all error cases in the synthesizers will output an error message but will instead cause the synthesis to stop (without crashing).

[Geremia]

A temporary workaround appears to be to refactor all variables as if they're all global, so function-local variables' identifiers are all unique. So, for your example:

module add(inout a(2), in b(2))
 wire c(2)

 a += (b + c)

module main(inout d(2), in e(2))
 call add(d, e)

Does SyReC not have the concept of function-local variables?

---

However, when I try refactorizing (from my #279 issue)

sha256.src (refactored)

module ror32(out o, in shift, in word)
  if (shift = 1) then
    o ^= ((word >> 1) | (word << 30))
  else
  if (shift = 2) then
    o ^= ((word >> 2) | (word << 29))
  else
  if (shift = 3) then
    o ^= ((word >> 3) | (word << 28))
  else
  if (shift = 4) then
    o ^= ((word >> 4) | (word << 27))
  else
  if (shift = 5) then
    o ^= ((word >> 5) | (word << 26))
  else
  if (shift = 6) then
    o ^= ((word >> 6) | (word << 25))
  else
  if (shift = 7) then
    o ^= ((word >> 7) | (word << 24))
  else
  if (shift = 8) then
    o ^= ((word >> 8) | (word << 23))
  else
  if (shift = 9) then
    o ^= ((word >> 9) | (word << 22))
  else
  if (shift = 10) then
    o ^= ((word >> 10) | (word << 21))
  else
  if (shift = 11) then
    o ^= ((word >> 11) | (word << 20))
  else
  if (shift = 12) then
    o ^= ((word >> 12) | (word << 19))
  else
  if (shift = 13) then
    o ^= ((word >> 13) | (word << 18))
  else
  if (shift = 14) then
    o ^= ((word >> 14) | (word << 17))
  else
  if (shift = 15) then
    o ^= ((word >> 15) | (word << 16))
  else
  if (shift = 16) then
    o ^= ((word >> 16) | (word << 15))
  else
  if (shift = 17) then
    o ^= ((word >> 17) | (word << 14))
  else
  if (shift = 18) then
    o ^= ((word >> 18) | (word << 13))
  else
  if (shift = 19) then
    o ^= ((word >> 19) | (word << 12))
  else
  if (shift = 20) then
    o ^= ((word >> 20) | (word << 11))
  else
  if (shift = 21) then
    o ^= ((word >> 21) | (word << 10))
  else
  if (shift = 22) then
    o ^= ((word >> 22) | (word << 9))
  else
  if (shift = 23) then
    o ^= ((word >> 23) | (word << 8))
  else
  if (shift = 24) then
    o ^= ((word >> 24) | (word << 7))
  else
  if (shift = 25) then
    o ^= ((word >> 25) | (word << 6))
  else
  if (shift = 26) then
    o ^= ((word >> 26) | (word << 5))
  else
  if (shift = 27) then
    o ^= ((word >> 27) | (word << 4))
  else
  if (shift = 28) then
    o ^= ((word >> 28) | (word << 3))
  else
  if (shift = 29) then
    o ^= ((word >> 29) | (word << 2))
  else
  if (shift = 30) then
    o ^= ((word >> 30) | (word << 1))
  else
  if (shift = 31) then
    o ^= (word >> 31)
  else
    o ^= word
  fi (shift = 31)
  fi (shift = 30)
  fi (shift = 29)
  fi (shift = 28)
  fi (shift = 27)
  fi (shift = 26)
  fi (shift = 25)
  fi (shift = 24)
  fi (shift = 23)
  fi (shift = 22)
  fi (shift = 21)
  fi (shift = 20)
  fi (shift = 19)
  fi (shift = 18)
  fi (shift = 17)
  fi (shift = 16)
  fi (shift = 15)
  fi (shift = 14)
  fi (shift = 13)
  fi (shift = 12)
  fi (shift = 11)
  fi (shift = 10)
  fi (shift = 9)
  fi (shift = 8)
  fi (shift = 7)
  fi (shift = 6)
  fi (shift = 5)
  fi (shift = 4)
  fi (shift = 3)
  fi (shift = 2)
  fi (shift = 1)

module Ch(out o_Ch, in x_Ch, in y_Ch, in z_Ch)
  o_Ch ^= (z_Ch ^ (x_Ch & (y_Ch ^ z_Ch)))

module Maj(out o_Maj, in x_Maj, in y_Maj, in z_Maj)
  o_Maj ^= ((x_Maj & y_Maj) | (z_Maj & (x_Maj | y_Maj)))

module e0(out o_e0, in x_e0)
  wire a_e0, b_e0, c_e0, s1_e0, s2_e0, s3_e0
  s1_e0 ^= 2 ; call ror32(a_e0, x_e0, s1_e0);
  s2_e0 ^= 13; call ror32(b_e0, x_e0, s2_e0);
  s3_e0 ^= 22; call ror32(c_e0, x_e0, s3_e0);
  o_e0 ^= (a_e0 ^ (b_e0 ^ c_e0))

module e1(out o_e1, in x_e1)
  wire a_e1, b_e1, c_e1, s1_e1, s2_e1
  s1_e1 ^= 7 ; call ror32(a_e1, x_e1, s1_e1);
  s2_e1 ^= 18; call ror32(b_e1, x_e1, s2_e1);
  o_e1 ^= (a_e1 ^ (b_e1 ^ c_e1))

module s0(out o_s0, in x_s0)
  wire a_s0, b_s0, s1_s0, s2_s0
  s1_s0 ^= 7 ; call ror32(a_s0, x_s0, s1_s0);
  s2_s0 ^= 18; call ror32(b_s0, x_s0, s2_s0);
  o_s0 ^= (a_s0 ^ (b_s0 ^ (x_s0 >> 3)))

module s1(out o_s1, in x_s1)
  wire a_s1, b_s1, s1_s1, s2_s1
  s1_s1 ^= 17; call ror32(a_s1, x_s1, s1_s1);
  s2_s1 ^= 19; call ror32(b_s1, x_s1, s2_s1);
  o_s1 ^= (a_s1 ^ (b_s1 ^ (x_s1 >> 10)))

module main(inout s[8], in input[16])
  wire i1, i2, i3, i4, s1o, s0o, wi1, wi3  // ← for blend loop
  wire a, b, c, d, e, f, g, h, t1, t2
  wire W[64], K[64]
  wire e1o, Cho, e0o, Majo
  wire zero
  K[0]  ^= 1116352408;  K[16] ^= 3835390401;  K[32] ^=  666307205;  K[48] ^=  430227734;
  K[1]  ^= 1899447441;  K[17] ^= 4022224774;  K[33] ^=  773529912;  K[49] ^=  506948616;
  K[2]  ^= 3049323471;  K[18] ^=  264347078;  K[34] ^= 1294757372;  K[50] ^=  659060556;
  K[3]  ^= 3921009573;  K[19] ^=  604807628;  K[35] ^= 1396182291;  K[51] ^=  883997877;
  K[4]  ^=  961987163;  K[20] ^=  770255983;  K[36] ^= 1695183700;  K[52] ^=  958139571;
  K[5]  ^= 1508970993;  K[21] ^= 1249150122;  K[37] ^= 1986661051;  K[53] ^= 1322822218;
  K[6]  ^= 2453635748;  K[22] ^= 1555081692;  K[38] ^= 2177026350;  K[54] ^= 1537002063;
  K[7]  ^= 2870763221;  K[23] ^= 1996064986;  K[39] ^= 2456956037;  K[55] ^= 1747873779;
  K[8]  ^= 3624381080;  K[24] ^= 2554220882;  K[40] ^= 2730485921;  K[56] ^= 1955562222;
  K[9]  ^=  310598401;  K[25] ^= 2821834349;  K[41] ^= 2820302411;  K[57] ^= 2024104815;
  K[10] ^=  607225278;  K[26] ^= 2952996808;  K[42] ^= 3259730800;  K[58] ^= 2227730452;
  K[11] ^= 1426881987;  K[27] ^= 3210313671;  K[43] ^= 3345764771;  K[59] ^= 2361852424;
  K[12] ^= 1925078388;  K[28] ^= 3336571891;  K[44] ^= 3516065817;  K[60] ^= 2428436474;
  K[13] ^= 2162078206;  K[29] ^= 3584528711;  K[45] ^= 3600352804;  K[61] ^= 2756734187;
  K[14] ^= 2614888103;  K[30] ^=  113926993;  K[46] ^= 4094571909;  K[62] ^= 3204031479;
  K[15] ^= 3248222580;  K[31] ^=  338241895;  K[47] ^=  275423344;  K[63] ^= 3329325298;

  // load init state
  for $i = 0 to 7 do
    s[$i] <=> zero
  rof;
  s[0] ^= 1779033703;  s[1] ^= 3144134277;  s[2] ^= 1013904242;  s[3] ^= 2773480762;
  s[4] ^= 1359893119;  s[5] ^= 2600822924;  s[6] ^=  528734635;  s[7] ^= 1541459225;

  // load the input
  for $i = 0 to 15 do
    W[$i] ^= input[$i]
  rof;

  // now blend
  for $i = 16 to 63 do
    i1 <=> zero; i1 ^= ($i - 2);
    i2 <=> zero; i2 ^= ($i - 7);
    i3 <=> zero; i3 ^= ($i - 15);
    i4 <=> zero; i4 ^= ($i - 16);
    wi1 <=> zero; wi1 ^= W[i1]; s1o <=> zero; call s1(s1o, wi1);
    wi3 <=> zero; wi3 ^= W[i3]; s0o <=> zero; call s0(s0o, wi3); 
    W[$i] ^= ((s1o + W[i2]) + (s0o + W[i4]))
  rof;

  // load the state i into our registers
  a ^= s[0];  b ^= s[1];  c ^= s[2];  d ^= s[3];
  e ^= s[4];  f ^= s[5];  g ^= s[6];  h ^= s[7];

  // now iterate
  for $i = 0 to 63 do
    e1o <=> zero; call e1(e1o, e);
    Cho <=> zero; call Ch(Cho, e, f, g);
    e0o <=> zero; call e0(e0o, a);
    Majo <=> zero; call Maj(Majo, a, b, c);
    t1 <=> zero; t1 ^= (((h + e1o) + Cho) + (K[$i] + W[$i]));
    t2 <=> zero; t2 ^= (e0o + Majo);
    h <=> zero; h ^= g;
    g <=> zero; g ^= f;
    f <=> zero; f ^= e;
    e <=> zero; e ^= (d + t1);
    d <=> zero; d ^= c;
    c <=> zero; c ^= b;
    b <=> zero; b ^= a;
    a <=> zero; a ^= (t1 + t2)
  rof;

  s[0] += a;  s[1] += b;  s[2] += c;  s[3] += d;
  s[4] += e;  s[5] += f;  s[6] += g;  s[7] += h

I still get "Failed to create qubits for parameters of main module of SyReC program".

[TooMuchDakka]

A temporary workaround appears to be to refactor all variables as if they're all global, so function-local variables' identifiers are all unique. So, for your example:

module add(inout a(2), in b(2))
 wire c(2)

 a += (b + c)

module main(inout d(2), in e(2))
 call add(d, e)

Does SyReC not have the concept of function-local variables?

However, when I try refactorizing (from my #279 issue)
sha256.src (refactored)

I still get "Failed to create qubits for parameters of main module of SyReC program".

• SyReC supports function-local variables but an error in processing of Call-/UncallStatements in the synthesis algorithm (as described in this issue) causes the synthesis to complete unsuccessfully (without providing a helpful error message) in some cases.
• Could you provide more information about the environment that you used to synthesis the refactored version of sha256.src or is it the same as in 🐛 "Failed to create qubits for parameters of main module of SyReC program" #279?

[Geremia]

@TooMuchDakka

• Could you provide more information about the environment that you used to synthesis the refactored version of sha256.src or is it the same as in 🐛 "Failed to create qubits for parameters of main module of SyReC program" #279?

I get the issue with mqt-core 3.0.3.dev94+ga06d0fdf, mqt.syrec 1.2.2.dev31+g995f203, and mqt.syrec 1.2.2.dev36+g0390120.