From 057f23d3ddabf8c89e5da371d724d1995e9655da Mon Sep 17 00:00:00 2001
From: Eduard-Mihai Burtescu <edy.burt@gmail.com>
Date: Mon, 12 Aug 2019 15:27:31 +0300
Subject: [PATCH] rustc_codegen_ssa: remove redundant `va_list_ref` field from
 `FunctionCx`.

---
 src/librustc_codegen_ssa/mir/block.rs | 12 +++++++-----
 src/librustc_codegen_ssa/mir/mod.rs   | 14 +-------------
 2 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index 0b9519f1c8079..7ebdfbdcdeb2d 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -1,3 +1,4 @@
+use rustc_data_structures::indexed_vec::Idx;
 use rustc::middle::lang_items;
 use rustc::ty::{self, Ty, TypeFoldable, Instance};
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, FnTypeExt};
@@ -224,14 +225,15 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     }
 
     fn codegen_return_terminator(&mut self, mut bx: Bx) {
+        // Call `va_end` if this is the definition of a C-variadic function.
         if self.fn_ty.c_variadic {
-            match self.va_list_ref {
-                Some(va_list) => {
+            // The `VaList` "spoofed" argument is just after all the real arguments.
+            let va_list_arg_idx = self.fn_ty.args.len();
+            match self.locals[mir::Local::new(1 + va_list_arg_idx)] {
+                LocalRef::Place(va_list) => {
                     bx.va_end(va_list.llval);
                 }
-                None => {
-                    bug!("C-variadic function must have a `va_list_ref`");
-                }
+                _ => bug!("C-variadic function must have a `VaList` place"),
             }
         }
         if self.fn_ty.ret.layout.abi.is_uninhabited() {
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
index 5f8ffaad3d4fd..4f3a8bdb540b5 100644
--- a/src/librustc_codegen_ssa/mir/mod.rs
+++ b/src/librustc_codegen_ssa/mir/mod.rs
@@ -81,10 +81,6 @@ pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
 
     /// Debug information for MIR scopes.
     scopes: IndexVec<mir::SourceScope, debuginfo::MirDebugScope<Bx::DIScope>>,
-
-    /// If this function is a C-variadic function, this contains the `PlaceRef` of the
-    /// "spoofed" `VaListImpl`.
-    va_list_ref: Option<PlaceRef<'tcx, Bx::Value>>,
 }
 
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
@@ -236,18 +232,13 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         scopes,
         locals: IndexVec::new(),
         debug_context,
-        va_list_ref: None,
     };
 
     let memory_locals = analyze::non_ssa_locals(&fx);
 
     // Allocate variable and temp allocas
     fx.locals = {
-        // FIXME(dlrobertson): This is ugly. Find a better way of getting the `PlaceRef` or
-        // `LocalRef` from `arg_local_refs`
-        let mut va_list_ref = None;
-        let args = arg_local_refs(&mut bx, &fx, &memory_locals, &mut va_list_ref);
-        fx.va_list_ref = va_list_ref;
+        let args = arg_local_refs(&mut bx, &fx, &memory_locals);
 
         let mut allocate_local = |local| {
             let decl = &mir.local_decls[local];
@@ -426,7 +417,6 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &mut Bx,
     fx: &FunctionCx<'a, 'tcx, Bx>,
     memory_locals: &BitSet<mir::Local>,
-    va_list_ref: &mut Option<PlaceRef<'tcx, Bx::Value>>,
 ) -> Vec<LocalRef<'tcx, Bx::Value>> {
     let mir = fx.mir;
     let tcx = fx.cx.tcx();
@@ -500,8 +490,6 @@ fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
             let va_list = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
             bx.set_var_name(va_list.llval, name);
             bx.va_start(va_list.llval);
-            // FIXME(eddyb) remove `va_list_ref`.
-            *va_list_ref = Some(va_list);
 
             arg_scope.map(|scope| {
                 let variable_access = VariableAccess::DirectVariable {