From 83a82457349afe5567bc5da2ece0f6366e879321 Mon Sep 17 00:00:00 2001
From: nella <simontupy64@gmail.com>
Date: Wed, 10 Jun 2026 14:46:04 +0200
Subject: [PATCH 1/2] Add muxcover regression test.

---
 tests/various/muxcover_index.ys | 87 +++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 tests/various/muxcover_index.ys

diff --git a/tests/various/muxcover_index.ys b/tests/various/muxcover_index.ys
new file mode 100644
index 000000000..041d497a5
--- /dev/null
+++ b/tests/various/muxcover_index.ys
@@ -0,0 +1,87 @@
+# https://github.com/YosysHQ/yosys/issues/964
+
+read_verilog -formal <<EOT
+module mux_index_8_2 #(parameter N=8, parameter W=2) (input [N*W-1:0] i, input [$clog2(N)-1:0] s, output [W-1:0] o);
+	assign o = i[s*W+:W];
+endmodule
+EOT
+
+prep
+design -save gold
+
+opt
+peepopt
+techmap
+opt
+muxcover -mux8
+clean
+opt_expr -mux_bool
+
+select -assert-count 2 t:$_MUX8_
+select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+
+techmap -map +/simcells.v t:$_MUX8_
+design -stash gate
+design -import gold -as gold
+design -import gate -as gate
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts miter
+
+design -reset
+read_verilog -formal <<EOT
+module mux_index_8_3 #(parameter N=8, parameter W=3) (input [N*W-1:0] i, input [$clog2(N)-1:0] s, output [W-1:0] o);
+	assign o = i[s*W+:W];
+endmodule
+EOT
+
+prep
+design -save gold
+
+opt
+peepopt
+techmap
+opt
+muxcover -mux8
+clean
+opt_expr -mux_bool
+
+select -assert-count 3 t:$_MUX8_
+select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+
+techmap -map +/simcells.v t:$_MUX8_
+design -stash gate
+design -import gold -as gold
+design -import gate -as gate
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts miter
+
+design -reset
+read_verilog -formal <<EOT
+module mux_index_8_4 #(parameter N=8, parameter W=4) (input [N*W-1:0] i, input [$clog2(N)-1:0] s, output [W-1:0] o);
+	assign o = i[s*W+:W];
+endmodule
+EOT
+
+prep
+design -save gold
+
+opt
+peepopt
+techmap
+opt
+muxcover -mux8
+clean
+opt_expr -mux_bool
+
+select -assert-count 4 t:$_MUX8_
+select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+
+techmap -map +/simcells.v t:$_MUX8_
+design -stash gate
+design -import gold -as gold
+design -import gate -as gate
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts miter

From 8f5d2d5894bc09555d01fb22b59036786e170b99 Mon Sep 17 00:00:00 2001
From: nella <simontupy64@gmail.com>
Date: Mon, 22 Jun 2026 11:12:00 +0200
Subject: [PATCH 2/2] Use -assert-none.

---
 tests/various/muxcover_index.ys | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tests/various/muxcover_index.ys b/tests/various/muxcover_index.ys
index 041d497a5..b8a9a2cb0 100644
--- a/tests/various/muxcover_index.ys
+++ b/tests/various/muxcover_index.ys
@@ -18,8 +18,8 @@ clean
 opt_expr -mux_bool
 
 select -assert-count 2 t:$_MUX8_
-select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
-select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+select -assert-none t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-none t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
 
 techmap -map +/simcells.v t:$_MUX8_
 design -stash gate
@@ -47,8 +47,8 @@ clean
 opt_expr -mux_bool
 
 select -assert-count 3 t:$_MUX8_
-select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
-select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+select -assert-none t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-none t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
 
 techmap -map +/simcells.v t:$_MUX8_
 design -stash gate
@@ -76,8 +76,8 @@ clean
 opt_expr -mux_bool
 
 select -assert-count 4 t:$_MUX8_
-select -assert-count 0 t:$_MUX_ t:$_MUX4_ t:$_MUX16_
-select -assert-count 0 t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
+select -assert-none t:$_MUX_ t:$_MUX4_ t:$_MUX16_
+select -assert-none t:$_AND_ t:$_OR_ t:$_XOR_ t:$_NAND_ t:$_NOR_ t:$_XNOR_
 
 techmap -map +/simcells.v t:$_MUX8_
 design -stash gate