From 822a6a12316aa043eea7f6aed4d730bc10a73d7b Mon Sep 17 00:00:00 2001 From: Xavier Leroy Date: Wed, 10 Jul 2019 15:43:03 +0200 Subject: x86_64: branchless implementation of floatofintu and intuoffloat MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The implementation uses float <-> signed 64-bit integer conversion instructions, and is both efficient and branchless. Based on a suggestion by Rémi Hutin. --- x86/SelectOp.vp | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) (limited to 'x86/SelectOp.vp') diff --git a/x86/SelectOp.vp b/x86/SelectOp.vp index 378590ce..31be8c32 100644 --- a/x86/SelectOp.vp +++ b/x86/SelectOp.vp @@ -40,6 +40,7 @@ Require Import Coqlib. Require Import Compopts. Require Import AST Integers Floats Builtins. Require Import Op CminorSel. +Require Archi. Local Open Scope cminorsel_scope. @@ -498,21 +499,27 @@ Nondetfunction floatofint (e: expr) := end. Definition intuoffloat (e: expr) := - Elet e - (Elet (Eop (Ofloatconst (Float.of_intu Float.ox8000_0000)) Enil) - (Econdition (CEcond (Ccompf Clt) (Eletvar 1 ::: Eletvar 0 ::: Enil)) - (intoffloat (Eletvar 1)) - (addimm Float.ox8000_0000 (intoffloat (subf (Eletvar 1) (Eletvar 0))))))%nat. + if Archi.splitlong then + Elet e + (Elet (Eop (Ofloatconst (Float.of_intu Float.ox8000_0000)) Enil) + (Econdition (CEcond (Ccompf Clt) (Eletvar 1 ::: Eletvar 0 ::: Enil)) + (intoffloat (Eletvar 1)) + (addimm Float.ox8000_0000 (intoffloat (subf (Eletvar 1) (Eletvar 0))))))%nat + else + Eop Olowlong (Eop Olongoffloat (e ::: Enil) ::: Enil). Nondetfunction floatofintu (e: expr) := match e with | Eop (Ointconst n) Enil => Eop (Ofloatconst (Float.of_intu n)) Enil | _ => - let f := Eop (Ofloatconst (Float.of_intu Float.ox8000_0000)) Enil in - Elet e - (Econdition (CEcond (Ccompuimm Clt Float.ox8000_0000) (Eletvar O ::: Enil)) - (floatofint (Eletvar O)) - (addf (floatofint (addimm (Int.neg Float.ox8000_0000) (Eletvar O))) f)) + if Archi.splitlong then + let f := Eop (Ofloatconst (Float.of_intu Float.ox8000_0000)) Enil in + Elet e + (Econdition (CEcond (Ccompuimm Clt Float.ox8000_0000) (Eletvar O ::: Enil)) + (floatofint (Eletvar O)) + (addf (floatofint (addimm (Int.neg Float.ox8000_0000) (Eletvar O))) f)) + else + Eop Ofloatoflong (Eop Ocast32unsigned (e ::: Enil) ::: Enil) end. Definition intofsingle (e: expr) := Eop Ointofsingle (e ::: Enil). -- cgit