mirror of https://github.com/xemu-project/xemu.git
45d1749c1c
Assume clzw being executed on a register that is not sign-extended, such as for the following sequence that uses (1ULL << 63) | 392 as the operand to clzw: bseti a2, zero, 63 addi a2, a2, 392 clzw a3, a2 The correct result of clzw would be 23, but the current implementation returns -32 (as it performs a 64bit clz, which results in 0 leading zero bits, and then subtracts 32). Fix this by changing the implementation to: 1. shift the original register up by 32 2. performs a target-length (64bit) clz 3. return 32 if no bits are set Marking this instruction as 'w-form' (i.e., setting ctx->w) would not correctly model the behaviour, as the instruction should not perform a zero-extensions on the input (after all, it is not a .uw instruction) and the result is always in the range 0..32 (so neither a sign-extension nor a zero-extension on the result will ever be needed). Consequently, we do not set ctx->w and mark the instruction as EXT_NONE. Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu> Reviewed-by: LIU Zhiwei<zhiwei_liu@c-sky.com> Message-id: 20210911140016.834071-4-philipp.tomsich@vrull.eu Signed-off-by: Alistair Francis <alistair.francis@wdc.com> |
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