tests/alumacc: Add broad merge test

Mixes input cells, signedness, input width, output width.
Within the things that are `random.choice`, they *should* always be equivalent, but add a seed arg anyway just in case one day they're not.

tests/alumacc/.gitignore

@@ -0,0 +1 @@
+uut_*.*

tests/alumacc/generate_mk.py

@@ -5,4 +5,100 @@ sys.path.append("..")
 
 import gen_tests_makefile
 
+import argparse
+import random
+from itertools import product
+
+TEMPLATE=r"""read_rtlil << EOT
+module \top
+  wire width {a_width} input 1 signed \a
+  wire width {b_width} input 2 signed \b
+  wire output 3 \x
+  wire width {y_width} output 4 \y
+  cell ${c1} \c1
+    parameter \A_SIGNED {c1_signed}
+    parameter \B_SIGNED {c1_signed}
+    parameter \A_WIDTH {a_width}
+    parameter \B_WIDTH {b_width}
+    parameter \Y_WIDTH 1
+    connect \A \a
+    connect \B \b
+    connect \Y \x
+  end
+  cell ${c2} \c2
+    parameter \A_SIGNED {c2_signed}
+    parameter \B_SIGNED {c2_signed}
+    parameter \A_WIDTH {a_width}
+    parameter \B_WIDTH {b_width}
+    parameter \Y_WIDTH {y_width}
+    connect \A \a
+    connect \B \b
+    connect \Y \y
+  end
+end
+EOT
+equiv_opt -assert alumacc
+design -load postopt
+{postopt_assert}
+"""
+
+EQ = ["eq", "eqx", "ne", "nex"]
+LGE = ["lt", "gt"]
+CMP = EQ + LGE
+ARITH = ["add", "sub"]
+SIGNED = [0, 1]
+WIDTH = list(range(1, 4))
+
+parser = argparse.ArgumentParser(formatter_class = argparse.ArgumentDefaultsHelpFormatter)
+parser.add_argument('-S', '--seed',  type = int, help = 'seed for PRNG')
+args = parser.parse_args()
+
+seed = args.seed
+if seed is None:
+    seed = random.randrange(sys.maxsize)
+print("alumacc PRNG seed: %d" % seed)
+random.seed(seed)
+
+count = 0
+for c1_signed, c2, c2_signed, a_width in product(
+    SIGNED, [EQ, LGE, ARITH], SIGNED, WIDTH
+):
+    c1 = random.choice(LGE)
+    if isinstance(c2, list):
+        c2 = random.choice(c2)
+
+    b_widths: list[int]
+    if a_width == 2:
+      b_widths = [1, 2, 3]
+    else:
+      b_widths = [a_width]
+    y_widths: list[int]
+    if c2 in CMP:
+        y_widths = [1]
+    else:
+        y_widths = b_widths
+
+    for b_width, y_width in product(b_widths, y_widths):
+        out_cells = "t:$alu"
+        for c in c1, c2:
+            if c in EQ:
+                # LGE cells will always remap to $alu, but EQ cells only will if merged
+                out_cells += f" t:${c}"
+
+        undersized = c2 in ARITH and y_width < max(a_width, b_width)
+        mixed_sign = c1_signed != c2_signed and a_width != b_width
+        if c2 != "add" and not undersized and not mixed_sign:
+            # cells correctly merged
+            postopt_assert = f"select -assert-count 1 {out_cells}"
+        else:
+            # postopt_assert = f"select -assert-count 2 {out_cells}"
+            # while currently correct, the above assertion would block potential improvements
+            postopt_assert = ""
+
+        with open(f"uut_{'s' if c1_signed else 'u'}{c1}_{'s' if c2_signed else 'u'}{c2}_{a_width}_{b_width}_{y_width}.ys", "w") as f:
+            print(str.format_map(TEMPLATE, locals()), file=f)
+            count = count + 1
+
+# print(count)
+
 gen_tests_makefile.generate(["--yosys-scripts"])