[HW] Incorrect SSA names for instance op.

[uenoku]

Reported in discord

$ cat bar.mlir
hw.module.extern @foo( in %in_0 : i32, out "out0" : i1 )
hw.module @bar(out "out0" : i1) {
    %t1 = hw.constant -3 : i32
    %t2 = hw.instance "%103" @foo(in_0 : %t1 : i32) -> (out0 : i1)
    hw.output  %t2 : i1
}

$ circt-opt bar.mlir
  hw.module @bar(out out0 : i1) {
    %c-3_i32 = hw.constant -3 : i32
    %25103.out0 = hw.instance "%103" @foo(in_0: %c-3_i32: i32) -> (out0: i1)
    hw.output %25103.out0 : i1
  }

$ circt-opt bar.mlir | circt-opt
  hw.module @bar(out out0 : i1) {
    %c-3_i32 = hw.constant -3 : i32
    %25103.out0 = hw.instance "%103" @foo(in_0: %c-3_i32: i32) -> (out0: i1)
    hw.output %25103.out0 : i1
  }

<stdin>:5:12: error: expected three consecutive dots for an ellipsis
    %25103.out0 = hw.instance "%103" @foo(in_0: %c-3_i32: i32) -> (out0: i1)

h/t Steven Derrien

[dtzSiFive]

I think MLIR's sanitizeIdentifier method has a bug where it fails to avoid leading digit, it checks for this in the name given but can still produce invalid identifier name if first character isn't valid (uses llvm::utohexstr) (which may produce a leading digit as we're seeing here).

We can workaround this by sanitizing ourselves but probably best to fix upstream.

[dtzSiFive]

Sent quick fix upstream: llvm/llvm-project#94795 .

[uenoku]

Awesome, thanks!

[dtzSiFive]

PR landed, this will be resolved with next LLVM bump.

[dtzSiFive]

Bump is now included, example works. Closing!