Construct a table like that shown in Figure C.21 to check for WAW stalls in the RISC V FP pipeline of Figure C.30. Do not consider FP divides.

Figure C.21

Figure C.30

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Situation No dependence Dependence requiring stall Dependence overcome by forwarding Dependence with accesses in order Example code sequence 1d x1,45(x2) x5,x6, x7 add sub x8, x6, x7 or x9,x6, x7 ld x1,45(x2) add x5,x1,x7 sub or ld add sub or x8, x6, x7 x9,x6, x7 x1,45 (x2) x5, x6, x7 x8, x1,x7 x9,x6, x7 ld x1,45(x2) add x5,x6, x7 sub x8, x6, x7 x9,x1,x7 or Action No hazard possible because no dependence exists on x1 in the immediately following three instructions Comparators detect the use of x1 in the add and stall the add (and sub and or) before the add begins EX Comparators detect use of x1 in sub and forward result of load to ALU in time for sub to begin EX No action required because the read of x1 by or occurs in the second half of the ID phase, while the write of the loaded data occurred in the first half