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Fix bad predbranch tracking on a jump to a predicted-taken non-taken 

branch which is halfword-sized and halfword-aligned, causing CIR
and PC to diverge.
This commit is contained in:
Luke Wren 2022-06-26 15:22:47 +01:00
parent 5455349961
commit 33cec49952
1 changed files with 9 additions and 4 deletions
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13
hdl/hazard3_frontend.v
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@ -455,7 +455,12 @@ wire [2:0] cir_bus_err_plus_fetch =
// And the same thing again for whether CIR contains a predicted-taken branch.
// One day I should clean up this copy/paste.
wire [1:0] fetch_predbranch_hw = fifo_empty ? mem_data_predbranch : fifo_predbranch[0];
wire [1:0] fetch_predbranch = fifo_empty ? mem_data_predbranch : fifo_predbranch[0];
wire [1:0] fetch_predbranch_aligned = {
fetch_predbranch[1],
fetch_data_hwvld[0] || ~|EXTENSION_C ? fetch_predbranch[0] : fetch_predbranch[1]
};
reg [2:0] cir_predbranch_reg;
wire [2:0] cir_predbranch_shifted =
@ -464,9 +469,9 @@ wire [2:0] cir_predbranch_shifted =
wire [2:0] cir_predbranch_plus_fetch =
!cir_room_for_fetch ? cir_predbranch_shifted :
level_next_no_fetch[1] && |EXTENSION_C ? {fetch_predbranch_hw[0], cir_predbranch_shifted[1:0]} :
level_next_no_fetch[0] && |EXTENSION_C ? {fetch_predbranch_hw, cir_predbranch_shifted[0]} :
{cir_predbranch_shifted[2], fetch_predbranch_hw};
level_next_no_fetch[1] && |EXTENSION_C ? {fetch_predbranch_aligned[0], cir_predbranch_shifted[1:0]} :
level_next_no_fetch[0] && |EXTENSION_C ? {fetch_predbranch_aligned, cir_predbranch_shifted[0]} :
{cir_predbranch_shifted[2], fetch_predbranch_aligned};
wire [1:0] fetch_fill_amount = cir_room_for_fetch && fetch_data_vld ? (
&fetch_data_hwvld ? 2'h2 : 2'h1