Simplify callee by removing is_indirect branch.

Author: Mark-Simulacrum

src/librustc_trans/callee.rs

@@ -16,7 +16,7 @@
 
 pub use self::CalleeData::*;
 
-use llvm::{self, ValueRef, get_param, get_params};
+use llvm::{self, ValueRef, get_params};
 use rustc::hir::def_id::DefId;
 use rustc::ty::subst::Substs;
 use rustc::traits;
@@ -342,13 +342,13 @@ fn trans_fn_once_adapter_shim<'a, 'tcx>(
     let mut llargs = get_params(fcx.llfn);
     let fn_ret = callee.ty.fn_ret();
     let fn_ty = callee.direct_fn_type(bcx.ccx, &[]);
-    let idx = fn_ty.ret.is_indirect() as usize;
+    let self_idx = fn_ty.ret.is_indirect() as usize;
     let env_arg = &orig_fn_ty.args[0];
     let llenv = if env_arg.is_indirect() {
-        llargs[idx]
+        llargs[self_idx]
     } else {
         let scratch = alloc_ty(&bcx, closure_ty, "self");
-        let mut llarg_idx = idx;
+        let mut llarg_idx = self_idx;
         env_arg.store_fn_arg(&bcx, &mut llarg_idx, scratch);
         scratch
     };
@@ -357,22 +357,15 @@ fn trans_fn_once_adapter_shim<'a, 'tcx>(
     // Adjust llargs such that llargs[self_idx..] has the call arguments.
     // For zero-sized closures that means sneaking in a new argument.
     if env_arg.is_ignore() {
-        if fn_ty.ret.is_indirect() {
-            llargs[0] = llenv;
-        } else {
-            llargs.insert(0, llenv);
-        }
+        llargs.insert(self_idx, llenv);
     } else {
-        llargs[idx] = llenv;
+        llargs[self_idx] = llenv;
     }
 
     // Call the by-ref closure body with `self` in a cleanup scope,
     // to drop `self` when the body returns, or in case it unwinds.
     let self_scope = fcx.schedule_drop_mem(llenv, closure_ty);
 
-    if fn_ty.ret.is_indirect() {
-        llargs.insert(0, get_param(fcx.llfn, 0));
-    }
     let llfn = callee.reify(bcx.ccx);
     let llret;
     if let Some(landing_pad) = self_scope.landing_pad {