From 9385be7a0cc95cb354c67cdbd5229a0f47ddd296 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Thu, 27 May 2021 10:31:47 -0400
Subject: [PATCH] Update compiler/rustc_middle/src/query/mod.rs
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Co-authored-by: Léo Lanteri Thauvin <leseulartichaut@gmail.com>
---
 compiler/rustc_middle/src/query/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 8138eeac3d650..04aa30170dc60 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -222,6 +222,7 @@ rustc_queries! {
 
     /// Fetch the THIR for a given body. If typeck for that body failed, returns an empty `Thir`.
     query thir_body(key: ty::WithOptConstParam<LocalDefId>) -> (&'tcx Steal<thir::Thir<'tcx>>, thir::ExprId) {
+        // Perf tests revealed that hashing THIR is inefficient (see #85729).
         no_hash
         desc { |tcx| "building THIR for `{}`", tcx.def_path_str(key.did.to_def_id()) }
     }