From a2ba4016a64f84193261db9a52196adc39cb5767 Mon Sep 17 00:00:00 2001
From: Pierre Roux
Date: Thu, 12 Sep 2019 19:02:18 +0200
Subject: Reimplement is_float

is_float was relying on Obj.tag triggering a check that we are in the
OCaml heap which is expensive. On extreme examples, this can lead to a
global 2x speedup.

Thanks to Maxime Dénès and Jacques-Henri Jourdan for their help in
diagnosing this.
---
 kernel/byterun/coq_float64.h | 4 ++++
 kernel/nativevalues.ml       | 6 ++----
 2 files changed, 6 insertions(+), 4 deletions(-)

(limited to 'kernel')

diff --git a/kernel/byterun/coq_float64.h b/kernel/byterun/coq_float64.h
index 6814c31642..9fc390bd33 100644
--- a/kernel/byterun/coq_float64.h
+++ b/kernel/byterun/coq_float64.h
@@ -29,4 +29,8 @@ DECLARE_FUNOP(fsqrt, sqrt(x))
 DECLARE_FUNOP(next_up, nextafter(x, INFINITY))
 DECLARE_FUNOP(next_down, nextafter(x, -INFINITY))
 
+value coq_is_double(value x) {
+  return Val_long(Is_double(x));
+}
+
 #endif /* _COQ_FLOAT64_ */
diff --git a/kernel/nativevalues.ml b/kernel/nativevalues.ml
index 1d4fb5d39c..6b9d49052d 100644
--- a/kernel/nativevalues.ml
+++ b/kernel/nativevalues.ml
@@ -517,10 +517,8 @@ let print x =
 
 (** Support for machine floating point values *)
 
-let is_float (x:t) =
-  let o = Obj.repr x in
-  Int.equal (Obj.tag o) Obj.double_tag
-[@@ocaml.inline always]
+external is_float : t -> bool = "coq_is_double"
+[@@noalloc]
 
 let to_float (x:t) = (Obj.magic x : Float64.t)
 [@@ocaml.inline always]
-- 
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