mir: `unused_generic_params` query

This commit implements the `unused_generic_params` query, an initial
version of polymorphization which detects when an item does not use
generic parameters and is being needlessly monomorphized as a result.

Signed-off-by: David Wood <david@davidtw.co>

3 files changed, 14 insertions, 13 deletions

diff --git a/src/librustc_codegen_ssa/meth.rs b/src/librustc_codegen_ssa/meth.rs
index 199dd8c7df4..cfa01280e5a 100644
--- a/src/librustc_codegen_ssa/meth.rs
+++ b/src/librustc_codegen_ssa/meth.rs
@@ -94,7 +94,8 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
                     def_id,
                     substs,
                 )
-                .unwrap(),
+                .unwrap()
+                .polymorphize(cx.tcx()),
             )
         })
     });
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index 7116bb8c925..e1de9677f80 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -543,7 +543,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 Some(
                     ty::Instance::resolve(bx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs)
                         .unwrap()
-                        .unwrap(),
+                        .unwrap()
+                        .polymorphize(bx.tcx()),
                 ),
                 None,
             ),
diff --git a/src/librustc_codegen_ssa/mir/rvalue.rs b/src/librustc_codegen_ssa/mir/rvalue.rs
index 4b2be7b5321..9c108998bc9 100644
--- a/src/librustc_codegen_ssa/mir/rvalue.rs
+++ b/src/librustc_codegen_ssa/mir/rvalue.rs
@@ -190,17 +190,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 if bx.cx().tcx().has_attr(def_id, sym::rustc_args_required_const) {
                                     bug!("reifying a fn ptr that requires const arguments");
                                 }
-                                OperandValue::Immediate(
-                                    bx.get_fn_addr(
-                                        ty::Instance::resolve_for_fn_ptr(
-                                            bx.tcx(),
-                                            ty::ParamEnv::reveal_all(),
-                                            def_id,
-                                            substs,
-                                        )
-                                        .unwrap(),
-                                    ),
+                                let instance = ty::Instance::resolve_for_fn_ptr(
+                                    bx.tcx(),
+                                    ty::ParamEnv::reveal_all(),
+                                    def_id,
+                                    substs,
                                 )
+                                .unwrap()
+                                .polymorphize(bx.cx().tcx());
+                                OperandValue::Immediate(bx.get_fn_addr(instance))
                             }
                             _ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
                         }
@@ -213,7 +211,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                     def_id,
                                     substs,
                                     ty::ClosureKind::FnOnce,
-                                );
+                                )
+                                .polymorphize(bx.cx().tcx());
                                 OperandValue::Immediate(bx.cx().get_fn_addr(instance))
                             }
                             _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),