From 0dbd696aaef47205c1430b53841423c7d25455ed Mon Sep 17 00:00:00 2001 From: Nilay Vaish Date: Wed, 29 Apr 2015 22:35:22 -0500 Subject: [PATCH] cpu: o3: single cycle default div microop latency on x86 This patch sets the default latency of the division microop to a single cycle on x86. This is because the division instructions DIV and IDIV have been implemented as loops of div microops, where each microop computes a single bit of the quotient. --- src/cpu/o3/FuncUnitConfig.py | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/cpu/o3/FuncUnitConfig.py b/src/cpu/o3/FuncUnitConfig.py index 34c56163d..0f5efb776 100644 --- a/src/cpu/o3/FuncUnitConfig.py +++ b/src/cpu/o3/FuncUnitConfig.py @@ -39,6 +39,7 @@ # Authors: Kevin Lim from m5.SimObject import SimObject +from m5.defines import buildEnv from m5.params import * from FuncUnit import * @@ -49,6 +50,15 @@ class IntALU(FUDesc): class IntMultDiv(FUDesc): opList = [ OpDesc(opClass='IntMult', opLat=3), OpDesc(opClass='IntDiv', opLat=20, issueLat=19) ] + + # DIV and IDIV instructions in x86 are implemented using a loop which + # issues division microops. The latency of these microops should really be + # one (or a small number) cycle each since each of these computes one bit + # of the quotient. + if buildEnv['TARGET_ISA'] in ('x86'): + opList[1].opLat=1 + opList[1].issueLat=1 + count=2 class FP_ALU(FUDesc): -- 2.30.2