; Load the old history for the associated static branch into ugpr1.
; Each entry in the branch history table is 4 bytes.  The table is
; stored at BHT_Offset + gp, where gp is the program's global pointer.

s4addq    BHT_Index, gp, ugpr0           ; ugpr0 <- ((BHT_Index * 4) + gp)
ldl       ugpr1, BHT_Offset(ugpr0)       ; ugpr1 <- memory[ugpr0 + BHT_Offset]


; Load the old PHT entry into ugpr3.  Each entry in the
; PHT is 1 byte.  The table is stored at PHT_Offset + gp.

addq      ugpr1, gp, ugpr2               ; ugpr2 <- (old_history [i.e., ugpr1] + gp)
ldbs      ugpr3, PHT_Offset(ugpr2)       ; ugpr3 <- memory[ugpr2 + PHT_Offset]

; Calculate the new history and store it in ugpr1.
cmple     zero, Br_Dir, ugpr4            ; ugpr4 <- ((Br_Dir == 1) ? 1 : 0)
s2addq    ugpr1, ugpr4, ugpr1            ; shift current branch direction into the history
zapnot    ugpr1, #0x07, ugpr1            ; mask off unused bits

; Do part of the address calculation for the new PHT entry.
; Store this value in ugpr4.

addq      ugpr1, gp, ugpr4               ; ugpr4 <- (new_history [i.e., ugpr1] + gp)

; Update the old PHT entry.  The value in the PHT entry
; ranges from -4 to 3, with negative values indicating that
; the branch should be predicted not taken.  Br_Dir is 1 if
; the branch is taken, and -1 if the branch is not taken.
; The new PHT value is stored in ugpr3.

addq      ugpr3, Br_Dir, ugpr3           ; add either 1 or -1 to the PHT entry
maxsb8    ugpr3, #3, ugpr3               ; if the value is greater than 3, set it to 3
minsb8    ugpr3, #-4, ugpr3              ; if the value is less than -4, set it to -4

; Write the old PHT entry back into the PHT.
stb       ugpr3, PHT_Offset(ugpr2)       ; memory[ugpr2 + PHT_Offset] <- ugpr3

; Read the new PHT entry and store the prediction.
ldbs      ugpr3, PHT_Offset(ugpr4)       ; ugpr3 <- memory[ugpr4 + PHT_Offset]
st_pc     ugpr3, Br_Addr                 ; write prediction cache

; Store the new history.
stl       ugpr1, BHT_Offset(ugpr0)       ; store new BHT entry back into the table