From 1a20d908b6eefe32807f906b7294c562256a7518 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Karel=20Ko=C4=8D=C3=AD?= Date: Fri, 16 Feb 2018 16:24:35 +0100 Subject: Fix forwarding checker for I and J and S* instructions THere are exceptions when we care about forwarding and when we don't. --- qtmips_machine/core.cpp | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) (limited to 'qtmips_machine/core.cpp') diff --git a/qtmips_machine/core.cpp b/qtmips_machine/core.cpp index 75f7173..273842d 100644 --- a/qtmips_machine/core.cpp +++ b/qtmips_machine/core.cpp @@ -305,20 +305,26 @@ void CorePipelined::step() { bool stall = false; if (hazard_unit != MachineConfig::HU_NONE) { // Note: We make exception with $0 as that has no effect when written and is used in nop instruction -// TODO rt should be compared onlu if instruction is R or it's S* -#define HAZARD(STAGE) ((STAGE).regwrite && (STAGE).rwrite != 0 && ((STAGE).rwrite == dt_d.inst.rs() || (STAGE).rwrite == dt_d.inst.rt())) // Note: We make exception with $0 as that has no effect and is used in nop instruction + +#define HAZARD(STAGE) ( \ + (STAGE).regwrite && (STAGE).rwrite != 0 && \ + ((STAGE).rwrite == dt_d.inst.rs() || ( \ + ((STAGE).inst.type() == Instruction::T_R || (STAGE).inst.is_store()) && \ + (STAGE).rwrite == dt_d.inst.rt()) \ + )) // Note: We make exception with $0 as that has no effect and is used in nop instruction + if (HAZARD(dt_e)) { // Hazard with instruction in execute stage if (hazard_unit == MachineConfig::HU_STALL_FORWARD) { - if (dt_e.memread) - stall = true; - else { - // Forward result value - if (dt_e.rwrite == dt_d.inst.rs()) - dt_d.val_rs = dt_e.alu_val; - if (dt_e.rwrite == dt_d.inst.rt()) - dt_d.val_rt = dt_e.alu_val; - } + if (dt_e.memread) // TODO extend by branch instructions + stall = true; + else { + // Forward result value + if (dt_e.rwrite == dt_d.inst.rs()) + dt_d.val_rs = dt_e.alu_val; + if (dt_e.rwrite == dt_d.inst.rt()) + dt_d.val_rt = dt_e.alu_val; + } } else stall = true; } @@ -346,7 +352,7 @@ void CorePipelined::step() { fetch(); // clear decode latch (insert nope to execute stage) dtDecodeInit(dt_d); - } + } } void CorePipelined::reset() { -- cgit v1.2.3