Imperas lockstep simulation hangs on rv64gc when minstret = 0xFFFFFFFFFFFFFFFF and then a csrrc is done on bit 63

[davidharrishmc]

The following program hangs in lockstep after the csrrc. minstret contains 0xFFFFFFFFFFFFFFFF, and then it tries to clear the most significant bit. If I uncomment the nop, it finishes normally. If I don't initialize minstret to all 1s, it also finishes.

wsim rv64gc hang.elf --lockstepverbose

.section .text.init
.global rvtest_entry_point

main:

	li t1, -1           # all 1s
	li t0, 1            # 1 in lsb
	slli t0, t0, 63
    csrrs t6, minstret, t1	# set all bits 
#    nop
	csrrc t6, minstret, t0 # clear msb

self_loop:
    j self_loop

hang.elf.gz