Limit multilib-gen-gen to more-useful ISA combinations

test/sim/common/multilib-gen-gen.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-# Generate a multilib configure line for riscv-gnu-toolchain with all
+# Generate a multilib configure line for riscv-gnu-toolchain with all useful
 # combinations of extensions supported by both Hazard3 and mainline GCC
 # (currently GCC 13.2). Use as:
 # ./configure ... --with-multilib-generator="$(path/to/multilib-gen-gen.py)"
@@ -11,21 +11,46 @@ options = [
 	"m",
 	"a",
 	"c",
-	"_zicsr",
-	"_zifencei",
-	"_zba",
-	"_zbb",
-	"_zbc",
-	"_zbs",
-	"_zbkb"
+	"zicsr",
+	"zifencei",
+	"zba",
+	"zbb",
+	"zbc",
+	"zbs",
+	"zbkb"
 ]
 
+# The relationship here is: do not build for LHS except when *all of* RHS is
+# also present. This cuts down on the number of configurations whilst
+# hopefully preserving ones that are useful for Hazard3 development.
+depends_on = {
+	"zbb":      ["m"                ],
+	"zba":      ["m"                ],
+	"zbkb":     ["zbb"              ],
+	"zbs":      ["zbb",             ],
+	"zbc":      ["zba", "zbb", "zbs"],
+	"zifencei": ["zicsr"            ],
+}
+
 l = []
 for i in range(2 ** len(options)):
 	isa = base
-	for j in range(len(options)):
-		if i & (1 << j):
-			isa += options[j]
-	l.append(isa + abi)
+	violates_dependencies = False
+	for j in (j for j in range(len(options)) if i & (1 << j)):
+		opt = options[j]
+		if opt in depends_on:
+			for dep in depends_on[opt]:
+				if not (i & (1 << options.index(dep))):
+					violates_dependencies = True
+					break
+		if violates_dependencies:
+			break
+		if len(opt) > 1:
+			isa += "_"
+		isa += opt
+	if not violates_dependencies:
+		l.append(isa + abi)
+
+assert((base + abi) in l)
 
 print(";".join(l))