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+Unexpected Behaviors when Using RISC-V Extension "zbs"
+### Description & Investigation
+
+I tried to run python3.12 on box64, and it crashed with SIGSEGV. Using `BOX64_DYNAREC_TEST=1`, I saw many differences about RIP:
+
+```txt
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001e44b1 (0f 82 82 03 00 00 8d b0)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001e44b7 | 0000003f001e4839
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001e4405 (0f 82 2d 01 00 00 83 ea)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001e440b | 0000003f001e4538
+Warning, difference between x64 Interpreter and Dynarec in 0x3f002683c7 (72 2b 2d 00 01 00 00 83)
+=======================================
+DIFF: Dynarec |  Interpreter
+(( omitted ))
+```
+
+These addresses are all in `libpython3.12.so` and `objdump` told me **they all almost look like**:
+
+```asm
+bt     %eax,%ecx
+jb     (( somewhere ))
+```
+
+The `bt` instruction should set the CF flag and the behavior of the following `jb` instruction depends on it. So I read current code:
+
+https://github.com/ptitSeb/box64/blob/d6b9fd2860dc097de8aebf147b3aa6d1741ea550/src/dynarec/rv64/dynarec_rv64_0f.c#L1720-L1739
+
+and saw `BEXT` will emit to `bext` instruction when "zbs" extension enabled.
+
+---
+
+When turning off the "zbs" extension, `libpython3.12` still crashed but the test log showed other differences irrelative with `bt` instruction:
+
+```txt
+(( BEGIN ))
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001ea3f3 (7e 17 83 fe 63 7f 12 89)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001ea40c | 0000003f001ea3f5
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001ea36f (0f 8f bb 00 00 00 39 c3)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001ea430 | 0000003f001ea375
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001ea3f3 (7e 17 83 fe 63 7f 12 89)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001ea40c | 0000003f001ea3f5
+Warning, difference between x64 Interpreter and Dynarec in 0x3f001ea36f (0f 8f bb 00 00 00 39 c3)
+=======================================
+DIFF: Dynarec |  Interpreter
+----------------------
+RIP: 0000003f001ea430 | 0000003f001ea375
+(( END ))
+```
+
+Again, `objdump` told me **they all look like**:
+
+```asm
+cmp    (( %esi or $0x63 here )),%eax
+jle/jg    (( somewhere ))
+```
+
+---
+
+Maybe at least we can say the `bt` instruction with "zbs" extension results in the my first "dynarec test" difference of this issue. And the latter one is still in investigation.
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