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[/] [theia_gpu/] [branches/] [beta_1.1/] [rtl/] [EXE/] [Module_InstructionFetch.v] - Rev 185
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`timescale 1ns / 1ps `include "aDefinitions.v" /********************************************************************************** Theia, Ray Cast Programable graphic Processing Unit. Copyright (C) 2010 Diego Valverde (diego.valverde.g@gmail.com) This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. ***********************************************************************************/ `define IFU_AFTER_RESET 0 `define IFU_INITIAL_STATE 1 `define IFU_WAIT_FOR_LAST_INSTRUCTION_LATCHED_BY_IDU 2 `define IFU_STALLED 3 `define IFU_FETCH_NEXT 4 `define FU_WAIT_FOR_EXE_UNIT 5 `define IFU_DONE 6 `define IFU_CHECK_FOR_JUMP_PENDING 7 `define IP_SET_VALUE_INITIAL_ADDRESS 0 `define IP_SET_VALUE_BRANCH_ADDRESS 1 //----------------------------------------------------------------------------- module InstructionFetchUnit ( input wire Clock, input wire Reset, input wire iBranchTaken, input wire iBranchNotTaken, input wire[`ROM_ADDRESS_WIDTH-1:0] iJumpIp, input wire iTrigger, input wire iIDUBusy, input wire iExeBusy, input wire[`INSTRUCTION_WIDTH-1:0] iEncodedInstruction, input wire[`ROM_ADDRESS_WIDTH-1:0] iInitialCodeAddress, input wire iDecodeUnitLatchedValues, output reg oExecutionDone, output wire oMicroCodeReturnValue, output wire oInstructionAvalable, output wire [`ROM_ADDRESS_WIDTH-1:0] oInstructionPointer, output wire[`INSTRUCTION_WIDTH-1:0] oCurrentInstruction ); //Alling the Jump Signal to the negedge of Clock, //I do this because I finded out the simulator //behaves funny if you change a value at the edge //of the clock and read from a bus that has changed wire rJumpNow; assign oCurrentInstruction = iEncodedInstruction; assign oMicroCodeReturnValue = iEncodedInstruction[0]; wire [`ROM_ADDRESS_WIDTH-1:0] wInstructionPointer; reg rEnable; assign oInstructionPointer = wInstructionPointer; reg rPreviousInstructionIsJump; `define INSTRUCTION_OPCODE iEncodedInstruction[`INSTRUCTION_WIDTH-1:`INSTRUCTION_WIDTH-`INSTRUCTION_OP_LENGTH] wire wLastInstruction; assign wLastInstruction = (`INSTRUCTION_OPCODE == 0) ? 1'b1 : 1'b0; wire rInstructionAvalable; assign rInstructionAvalable = (iTrigger || iDecodeUnitLatchedValues) && rEnable; //if it is jump delay 1 cycle wire wInstructionAvalableDelayed_1Cycle; wire wInstructionAvalableDelayed_2Cycle; wire wInstructionAvalableDelayed_3Cycle; wire wInstructionAvalableDelayed_4Cycle; wire wJumpNow_Delayed_1Cycle,wJumpNow_Delayed_2Cycle,wJumpNow_Delayed_3Cycle; FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelayJump ( .Clock( Clock ), .Clear( Reset ), .D( rJumpNow ), .Q( wJumpNow_Delayed_1Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelayJump2 ( .Clock( Clock ), .Clear( Reset ), .D( wJumpNow_Delayed_1Cycle ), .Q( wJumpNow_Delayed_2Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelayJump3 ( .Clock( Clock ), .Clear( Reset ), .D( wJumpNow_Delayed_2Cycle ), .Q( wJumpNow_Delayed_3Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelay1 ( .Clock( Clock ), .Clear( Reset ), .D( rInstructionAvalable ), .Q( wInstructionAvalableDelayed_1Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelay2 ( .Clock( Clock ), .Clear( Reset ), .D( wInstructionAvalableDelayed_1Cycle ), .Q( wInstructionAvalableDelayed_2Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelay3 ( .Clock( Clock ), .Clear( Reset ), .D( wInstructionAvalableDelayed_2Cycle ), .Q( wInstructionAvalableDelayed_3Cycle ) ); FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelay4A ( .Clock( Clock ), .Clear( Reset ), .D( wInstructionAvalableDelayed_3Cycle ), .Q( wInstructionAvalableDelayed_4Cycle ) ); assign oInstructionAvalable = (wInstructionAvalableDelayed_1Cycle && !rJumpNow) || (wInstructionAvalableDelayed_3Cycle && wJumpNow_Delayed_2Cycle); wire wInstructionAvalableDelayed; FFD_POSEDGE_ASYNC_RESET # ( 1 ) FFDelay4 ( .Clock( Clock ), .Clear( Reset ), .D( oInstructionAvalable ), .Q( wInstructionAvalableDelayed ) ); //---------------------------------------------- assign rJumpNow = iBranchTaken && !iBranchNotTaken; //This sucks, should be improved wire JumpInstructinDetected; assign JumpInstructinDetected = ( `INSTRUCTION_OPCODE == `JGEX || `INSTRUCTION_OPCODE == `JLEX || `INSTRUCTION_OPCODE == `JGEY || `INSTRUCTION_OPCODE == `JLEY || `INSTRUCTION_OPCODE == `JGEZ || `INSTRUCTION_OPCODE == `JLEZ || `INSTRUCTION_OPCODE == `JEQX || `INSTRUCTION_OPCODE == `JNEX || `INSTRUCTION_OPCODE == `JEQY || `INSTRUCTION_OPCODE == `JNEY || `INSTRUCTION_OPCODE == `JEQZ || `INSTRUCTION_OPCODE == `JNEZ ) ; //Stall logic. //it basically tells IFU to stall on Branches. //The Stall begins when a Branch instruction //is detected, the Stall ends when EXE tells us it made //a branch taken or branch not taken decision wire wStall; assign wStall = JumpInstructinDetected && !iBranchTaken && !iBranchNotTaken; //Increment the IP everytime IDU tells us it has Latched the previous I we gave him, //except when we reached the last instruction in the flow, or we are in a Stall wire wIncrementInstructionPointer; assign wIncrementInstructionPointer = (wStall || wLastInstruction) ? 1'b0 : iDecodeUnitLatchedValues; //------------------------------------------------- wire wIP_AlternateValue; wire wIP_SetValueSelector; wire [`ROM_ADDRESS_WIDTH-1:0] wInstructionPointerAlternateValue; MUXFULLPARALELL_16bits_2SEL InstructionPointerSetValueMUX ( .Sel( wIP_SetValueSelector ), .I1( iInitialCodeAddress ), .I2( iJumpIp ), .O1( wInstructionPointerAlternateValue ) ); reg rIpControl; MUXFULLPARALELL_1Bit_1SEL InstructionPointerControlMUX ( .Sel( rIpControl ), .I1( 1'b0 ), .I2( iBranchTaken ), .O1( wIP_SetValueSelector ) ); UPCOUNTER_POSEDGE # (16) InstructionPointer ( .Clock(wIncrementInstructionPointer || wJumpNow_Delayed_1Cycle || iTrigger), .Reset(iTrigger || wJumpNow_Delayed_1Cycle ), .Enable(1'b1), .Initial(wInstructionPointerAlternateValue), .Q(wInstructionPointer) ); reg [5:0] CurrentState, NextState; //------------------------------------------------ always @(posedge Clock or posedge Reset) begin if (Reset) CurrentState <= `IFU_AFTER_RESET; else CurrentState <= NextState; end //------------------------------------------------ always @ ( * ) begin case ( CurrentState ) //------------------------------------ `IFU_AFTER_RESET: begin rEnable <= iTrigger; rIpControl <= `IP_SET_VALUE_INITIAL_ADDRESS;//0; oExecutionDone <= 0; if (iTrigger) NextState <= `IFU_INITIAL_STATE; else NextState <= `IFU_AFTER_RESET; end //------------------------------------ `IFU_INITIAL_STATE: begin rEnable <= 1; rIpControl <= `IP_SET_VALUE_BRANCH_ADDRESS; //1; oExecutionDone <= 0; //We reached last instrcution (RETURN), and IDU latched the one before that if ( wLastInstruction && iDecodeUnitLatchedValues && !rJumpNow ) NextState <= `IFU_WAIT_FOR_LAST_INSTRUCTION_LATCHED_BY_IDU; else NextState <= `IFU_INITIAL_STATE; end //------------------------------------ //Here, we wait until IDU latches the last //instruction, ie. the RETURN instruction `IFU_WAIT_FOR_LAST_INSTRUCTION_LATCHED_BY_IDU: begin rEnable <= ~iDecodeUnitLatchedValues; rIpControl <= `IP_SET_VALUE_BRANCH_ADDRESS; oExecutionDone <= 0; if ( iDecodeUnitLatchedValues && !rJumpNow)//&& !iExeBusy && !iIDUBusy ) NextState <= `IFU_DONE; else if ( rJumpNow ) NextState <= `IFU_INITIAL_STATE; else NextState <= `IFU_WAIT_FOR_LAST_INSTRUCTION_LATCHED_BY_IDU; end //------------------------------------ `IFU_DONE: begin rEnable <= 0; rIpControl <= `IP_SET_VALUE_BRANCH_ADDRESS; oExecutionDone <= !iExeBusy && !iIDUBusy;//1'b1; if (!iExeBusy && !iIDUBusy) NextState <= `IFU_AFTER_RESET; else NextState <= `IFU_DONE; end //------------------------------------ default: begin rEnable <= 0; rIpControl <= `IP_SET_VALUE_INITIAL_ADDRESS; //0; oExecutionDone <= 0; NextState <= `IFU_AFTER_RESET; end //------------------------------------ endcase end// always //------------------------------------------------------ // // `ifdef DEBUG2 always @ ( negedge iTrigger or negedge iDecodeUnitLatchedValues ) begin $write("(%dns %d)",$time,oInstructionPointer); end always @ ( negedge wLastInstruction ) begin $display(" %dns RETURN %d",$time,oMicroCodeReturnValue); end `endif `ifdef DEBUG2 always @ (posedge wStall) begin $write("<S>"); end `endif endmodule //-------------------------------------------------------------------------------
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