From 22a2cc1897f0d9f568ebfb807673e84f6ada491a Mon Sep 17 00:00:00 2001
From: Pierre-Marie Pédrot
Date: Wed, 27 Jan 2016 09:36:47 +0100
Subject: Fix bug #4537: Coq 8.5 is slower in typeclass resolution.

The performance enhancement introduced by a895b2c0 for non-polymorphic hints
was actually causing a huge regression in the polymorphic case (and was marked
as such). We fix this by only substituting the metas from the evarmap instead
of the whole evarmap.
---
 tactics/auto.ml | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

(limited to 'tactics')

diff --git a/tactics/auto.ml b/tactics/auto.ml
index 2d92387c03..647ff97148 100644
--- a/tactics/auto.ml
+++ b/tactics/auto.ml
@@ -85,11 +85,14 @@ let connect_hint_clenv poly (c, _, ctx) clenv gl =
       let (subst, ctx) = Universes.fresh_universe_context_set_instance ctx in
       let map c = Vars.subst_univs_level_constr subst c in
       let evd = Evd.merge_context_set Evd.univ_flexible evd ctx in
-      let clenv = { clenv with evd = evd ; env = Proofview.Goal.env gl } in
-      (** FIXME: We're being inefficient here because we substitute the whole
-          evar map instead of just its metas, which are the only ones
-          mentioning the old universes. *)
-      Clenv.map_clenv map clenv, map c
+      (** Only metas are mentioning the old universes. *)
+      let clenv = {
+        templval = Evd.map_fl map clenv.templval;
+        templtyp = Evd.map_fl map clenv.templtyp;
+        evd = Evd.map_metas map evd;
+        env = Proofview.Goal.env gl;
+      } in
+      clenv, map c
     else
       let evd = Evd.merge_context_set Evd.univ_flexible evd ctx in
       { clenv with evd = evd ; env = Proofview.Goal.env gl }, c
-- 
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