Rollup merge of #137549 - oli-obk:llvm-ffi, r=davidtwco

Clean up various LLVM FFI things in codegen_llvm

cc ```@ZuseZ4``` I touched some autodiff parts

The major change of this PR is [bfd88ce](bfd88cead0) which makes `CodegenCx` generic just like `GenericBuilder`

The other commits mostly took advantage of the new feature of making extern functions safe, but also just used some wrappers that were already there and shrunk unsafe blocks.

best reviewed commit-by-commit

compiler/rustc_codegen_gcc/src/abi.rs

@@ -16,7 +16,7 @@ use crate::context::CodegenCx;
 use crate::intrinsic::ArgAbiExt;
 use crate::type_of::LayoutGccExt;
 
-impl<'a, 'gcc, 'tcx> AbiBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
+impl AbiBuilderMethods for Builder<'_, '_, '_> {
     fn get_param(&mut self, index: usize) -> Self::Value {
         let func = self.current_func();
         let param = func.get_param(index as i32);

compiler/rustc_codegen_gcc/src/common.rs

@@ -59,7 +59,7 @@ pub fn type_is_pointer(typ: Type<'_>) -> bool {
     typ.get_pointee().is_some()
 }
 
-impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
+impl<'gcc, 'tcx> ConstCodegenMethods for CodegenCx<'gcc, 'tcx> {
     fn const_null(&self, typ: Type<'gcc>) -> RValue<'gcc> {
         if type_is_pointer(typ) { self.context.new_null(typ) } else { self.const_int(typ, 0) }
     }
@@ -257,7 +257,7 @@ impl<'gcc, 'tcx> ConstCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         }
     }
 
-    fn const_data_from_alloc(&self, alloc: ConstAllocation<'tcx>) -> Self::Value {
+    fn const_data_from_alloc(&self, alloc: ConstAllocation<'_>) -> Self::Value {
         const_alloc_to_gcc(self, alloc)
     }
 

compiler/rustc_codegen_gcc/src/consts.rs

@@ -302,9 +302,9 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
     }
 }
 
-pub fn const_alloc_to_gcc<'gcc, 'tcx>(
-    cx: &CodegenCx<'gcc, 'tcx>,
-    alloc: ConstAllocation<'tcx>,
+pub fn const_alloc_to_gcc<'gcc>(
+    cx: &CodegenCx<'gcc, '_>,
+    alloc: ConstAllocation<'_>,
 ) -> RValue<'gcc> {
     let alloc = alloc.inner();
     let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);

compiler/rustc_codegen_gcc/src/type_.rs

@@ -123,7 +123,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
     }
 }
 
-impl<'gcc, 'tcx> BaseTypeCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
+impl<'gcc, 'tcx> BaseTypeCodegenMethods for CodegenCx<'gcc, 'tcx> {
     fn type_i8(&self) -> Type<'gcc> {
         self.i8_type
     }