DIV and REM: erronous results for -1/1

Created by: ASintzoff

When performing integer division -1/1, the quotient should be -1 and the remainder should be 0.

The observed results are not the expected ones:

• quotient: 0
• remainder: -1

These results are obtained thanks to the riscv-compliance test suite.

• https://github.com/riscv/riscv-compliance/blob/master/riscv-test-suite/rv32im/src/DIV.S
• https://github.com/riscv/riscv-compliance/blob/master/riscv-test-suite/rv32im/src/REM.S

Extract of riscv-compliance rv32im/DIV.S test log:

core   0: 0x0000000080000182 (0x000057fd) c.li    a5, -1
3 0x0000000080000182 (0x000057fd) x15 0xffffffffffffffff
core   0: 0x0000000080000184 (0x00004705) c.li    a4, 1
3 0x0000000080000184 (0x00004705) x14 0x0000000000000001
core   0: 0x0000000080000186 (0x02e7c733) div     a4, a5, a4
3 0x0000000080000186 (0x02e7c733) x14 0x0000000000000000

And rv32im/REM.S test log:

core   0: 0x0000000080000182 (0x000057fd) c.li    a5, -1
3 0x0000000080000182 (0x000057fd) x15 0xffffffffffffffff
core   0: 0x0000000080000184 (0x00004705) c.li    a4, 1
3 0x0000000080000184 (0x00004705) x14 0x0000000000000001
core   0: 0x0000000080000186 (0x02e7e733) rem     a4, a5, a4
3 0x0000000080000186 (0x02e7e733) x14 0xffffffffffffffff