[RV64_DYNAREC] Minor optimizations to sign mask extraction instructio… #5501

Job	Run time
build (X64, Release, ubuntu-latest)	2m 12s
build (X64, Trace, ubuntu-latest)	2m 29s
build (X64, Box32, ubuntu-latest)	3m 8s
build (RISCV, Release, ubuntu-latest)	8m 49s
build (RISCV, Trace, ubuntu-latest)	9m 52s
build (RISCV, StaticBuild, ubuntu-latest)	6m 2s
build (RISCV, Box32, ubuntu-latest)	9m 24s
build (RK3588, Release, ubuntu-22.04-arm)	6m 21s
build (RK3588, Trace, ubuntu-22.04-arm)	5m 41s
build (RK3588, StaticBuild, ubuntu-22.04-arm)	3m 57s
build (RK3588, Box32, ubuntu-22.04-arm)	5m 24s
build (ARM64, Release, ubuntu-22.04-arm)	6m 9s
build (ARM64, Trace, ubuntu-22.04-arm)	6m 13s
build (ARM64, StaticBuild, ubuntu-22.04-arm)	3m 29s
build (ARM64, Box32, ubuntu-22.04-arm)	5m 26s
build (ANDROID, Release, ubuntu-latest)	5m 7s
build (ANDROID, Trace, ubuntu-latest)	2m 46s
build (TERMUX, Release, ubuntu-latest)	2m 24s
build (TERMUX, Trace, ubuntu-latest)	2m 39s
build (LARCH64, Release, ubuntu-latest)	4m 20s
build (LARCH64, Trace, ubuntu-latest)	5m 12s
build (LARCH64, StaticBuild, ubuntu-latest)	5m 11s
build (LARCH64, Box32, ubuntu-latest)	4m 19s
build (ANDROID_GLIBC, Release, ubuntu-22.04-arm)	5m 43s
build (ANDROID_GLIBC, Trace, ubuntu-22.04-arm)	6m 26s
build (ANDROID_GLIBC, StaticBuild, ubuntu-22.04-arm)	3m 14s
build (ANDROID_GLIBC, Box32, ubuntu-22.04-arm)	6m 10s
	2h 18m 7s

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