From feeaa4db3cb990463871e35b16b3449023cb791d Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri, 26 Aug 2022 10:37:51 +1000
Subject: [PATCH] Simplify arg capacity calculations.

Currently they try to be very precise. But they are wrong, i.e. they
don't match what's happening in the loop below. This code isn't hot
enough for it to matter that much.
---
 compiler/rustc_codegen_gcc/src/abi.rs  | 22 +++-------------------
 compiler/rustc_codegen_llvm/src/abi.rs |  7 ++-----
 2 files changed, 5 insertions(+), 24 deletions(-)

diff --git a/compiler/rustc_codegen_gcc/src/abi.rs b/compiler/rustc_codegen_gcc/src/abi.rs
index 7f313583c82..87b730d29cd 100644
--- a/compiler/rustc_codegen_gcc/src/abi.rs
+++ b/compiler/rustc_codegen_gcc/src/abi.rs
@@ -107,26 +107,10 @@ pub trait FnAbiGccExt<'gcc, 'tcx> {
 impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
     fn gcc_type(&self, cx: &CodegenCx<'gcc, 'tcx>) -> (Type<'gcc>, Vec<Type<'gcc>>, bool, FxHashSet<usize>) {
         let mut on_stack_param_indices = FxHashSet::default();
-        let args_capacity: usize = self.args.iter().map(|arg|
-            if arg.pad.is_some() {
-                1
-            }
-            else {
-                0
-            } +
-            if let PassMode::Pair(_, _) = arg.mode {
-                2
-            } else {
-                1
-            }
-        ).sum();
+
+        // This capacity calculation is approximate.
         let mut argument_tys = Vec::with_capacity(
-            if let PassMode::Indirect { .. } = self.ret.mode {
-                1
-            }
-            else {
-                0
-            } + args_capacity,
+            self.args.len() + if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 }
         );
 
         let return_ty =
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 2353362f83b..a06b07c1149 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -328,12 +328,9 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         let args =
             if self.c_variadic { &self.args[..self.fixed_count as usize] } else { &self.args };
 
-        let args_capacity: usize = args.iter().map(|arg|
-            if arg.pad.is_some() { 1 } else { 0 } +
-            if let PassMode::Pair(_, _) = arg.mode { 2 } else { 1 }
-        ).sum();
+        // This capacity calculation is approximate.
         let mut llargument_tys = Vec::with_capacity(
-            if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 } + args_capacity,
+            self.args.len() + if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 },
         );
 
         let llreturn_ty = match &self.ret.mode {