Refactor Sigdata methods with sigset (#5307)

* Refactor sigdata methods

* Update cranelift/codegen/src/machinst/abi.rs

Co-authored-by: Jamey Sharp <jamey@minilop.net>

* Address comments

Co-authored-by: Jamey Sharp <jamey@minilop.net>

Author: tnachen

cranelift/codegen/src/isa/s390x/lower/isle.rs

@@ -129,7 +129,7 @@ impl generated_code::Context for IsleContext<'_, '_, MInst, Flags, IsaFlags, 6>
         for i in 0..self.lower_ctx.sigs()[*abi].num_rets() {
             if let &ABIArg::Slots {
                 ref slots, purpose, ..
-            } = &self.lower_ctx.sigs()[*abi].get_ret(self.lower_ctx.sigs(), i)
+            } = &self.lower_ctx.sigs().get_ret(*abi, i)
             {
                 if purpose == ArgumentPurpose::StructReturn {
                     continue;
@@ -192,8 +192,10 @@ impl generated_code::Context for IsleContext<'_, '_, MInst, Flags, IsaFlags, 6>
         defs: &CallRetList,
         opcode: &Opcode,
     ) -> BoxCallInfo {
-        let clobbers =
-            self.lower_ctx.sigs()[*abi].call_clobbers::<S390xMachineDeps>(self.lower_ctx.sigs());
+        let clobbers = self
+            .lower_ctx
+            .sigs()
+            .call_clobbers::<S390xMachineDeps>(*abi);
         Box::new(CallInfo {
             dest: name.clone(),
             uses: uses.clone(),
@@ -214,8 +216,10 @@ impl generated_code::Context for IsleContext<'_, '_, MInst, Flags, IsaFlags, 6>
         defs: &CallRetList,
         opcode: &Opcode,
     ) -> BoxCallIndInfo {
-        let clobbers =
-            self.lower_ctx.sigs()[*abi].call_clobbers::<S390xMachineDeps>(self.lower_ctx.sigs());
+        let clobbers = self
+            .lower_ctx
+            .sigs()
+            .call_clobbers::<S390xMachineDeps>(*abi);
         Box::new(CallIndInfo {
             rn: target,
             uses: uses.clone(),