doc: add more sample ir and graph files

doc/sample/graph/1.mie

@@ -0,0 +1,38 @@
+select.graph {
+	%entry = +select.entry -> #select.chain
+
+	%0 = +select.register @0 : i32 -> #select.register
+	%1 = +select.register @1 : i32 -> #select.register
+
+	%v.0, %c.0 = +select.register.read %entry, %0 \
+		: (#select.chain, #select.register) \
+		-> (i32, #select.chain)
+
+	%v.1, %c.1 = +select.register.read %entry, %1 \
+		: (#select.chain, #select.register) \
+		-> (i32, #select.chain)
+
+	%2 = +select.register @2 : i32
+
+	%v.2, %c.2 = +select.register.read %entry, %2 \
+		: (#select.chain, #select.register) \
+		-> (#select.register, #select.chain)
+
+	%v.3 = arith.build-pair %v.0, %v.1 : (i32, i32) -> i64
+
+	%v.4 = arith.truncate %v.2 : i64 -> i32
+
+	%v.5 = arith.mul %v.4, %v.3 : (i32, i32) -> i32
+
+	%x0 = +select.mach-register @x0 : i32 -> #select.register
+
+	%c.3, %g.0 = +select.register.write %entry, %x0, %v.5 \
+		: (#select.chain, #select.register, i32) \
+		-> (#select.chain, #select.glue)
+
+	%c.4 = *risc-v.RET %c.3, %x0, %g.0 \
+		: (#select.chain, #select.register, #select.glue) \
+		-> #select.chain
+
+	+select.graph-root %c.4 : #select.chain
+}