Regression (crash) in `opt_expr` in Yosys 0.54

[whitequark]

Version

Yosys 0.54 (git sha1 db72ec3, ccache clang 18.1.3 -O3 -flto -flto)

On which OS did this happen?

Linux

Reproduction Steps

Reproducer: video-rgb-input.il.txt

yosys video-rgb-input.il -p proc

(Extracted from failing CI in https://github.com/GlasgowEmbedded/glasgow/actions/runs/15547978782/job/43773062575)

Expected Behavior

Works (which it did in 0.53).

Actual Behavior

...

2.12. Executing OPT_EXPR pass (perform const folding).
Optimizing module top.cd_sync.clk_buf.
Optimizing module top.cd_sync.
Optimizing module top.U$5.U$7.
Optimizing module top.U$5.U$6.
Optimizing module top.U$5.U$5.
Optimizing module top.U$5.U$4.
Optimizing module top.U$5.dck_buffer.io.
Optimizing module top.U$5.dck_buffer.
Optimizing module top.U$5.b_buffer.io.
Optimizing module top.U$5.b_buffer.
Optimizing module top.U$5.g_buffer.io.
Optimizing module top.U$5.g_buffer.
Optimizing module top.U$5.r_buffer.io.
Optimizing module top.U$5.r_buffer.
Optimizing module top.U$5.
<suppressed ~7 debug messages>
ERROR: Assert `!empty()' failed in ../yosys-src/kernel/rtlil.cc:5532.

[whitequark]

It crashes here:

yosys/passes/opt/opt_expr.cc

Lines 1307 to 1315 in c561ba8

	if (cell->type.in(ID($shl), ID($shr), ID($sshl), ID($sshr), ID($shift), ID($shiftx)) && (keepdc ? assign_map(cell->getPort(ID::B)).is_fully_def() : assign_map(cell->getPort(ID::B)).is_fully_const()))
	{
	bool sign_ext = cell->type == ID($sshr) && cell->getParam(ID::A_SIGNED).as_bool();
	RTLIL::SigSpec sig_b = assign_map(cell->getPort(ID::B));
	const bool b_sign_ext = cell->type.in(ID($shift), ID($shiftx)) && cell->getParam(ID::B_SIGNED).as_bool();
	// We saturate the value to prevent overflow, but note that this could
	// cause incorrect opimization in the impractical case that A is 2^32 bits
	// wide
	int shift_bits = sig_b.as_int_saturating(b_sign_ext);

Presumably because of this cell:

  cell $shr $85
    parameter \A_SIGNED 0
    parameter \B_SIGNED 0
    parameter \A_WIDTH 15
    parameter \B_WIDTH 0
    parameter \Y_WIDTH 15
    connect \A \pixel [14:0]
    connect \B {  }
    connect \Y $20
  end

Presumably introduced in: 0dcd94b (#5101)

[KrystalDelusion]

@georgerennie FYI

[robtaylor]

Any chance we could get a quick point release to fix this?

[whitequark]

It's not even merged yet. But once it's merged, if you remind me, I can kick off a yowasp build for a git commit with the fix easily enough.

[KrystalDelusion]

Any chance we could get a quick point release to fix this?

FWIW Yosys does (minor point) releases every month, and as far as I know has never made a release for a patch