clang miscompilation when using experimental-mv abi #71124
Description
repro.tar.zst uploaded at https://files.catbox.moe/5asjku.zst
The above tarball contains an archive with all combined dependencies, and a CPP-processed C source file to reproduce the bug. The bug happens on both clang-17 and trunk. No wasi-sdk build or wasi-libc sysroot is needed to reproduce and diagnose the bug, vanilla clang with wasm32 target shall do:
clang --target=wasm32 \
-Oz -mmultivalue -c hgcd2.orig.c -o hgcd2.o -Xclang -target-abi -Xclang experimental-mv
wasm-ld -m wasm32 ghc_5.o repro.a hgcd2.o -o integerPowMod.wasm
wasmtime integerPowMod.wasm
The above example produces invalid code and crashes with:
Error: failed to run main module `integerPowMod.wasm`
Caused by:
0: failed to invoke command default
1: error while executing at wasm backtrace:
0: 0x15b647 - <unknown>!abort
1: 0x15216d - <unknown>!dlfree
2: 0x15012d - <unknown>!free
3: 0x5d161 - <unknown>!__gmp_default_free
4: 0x5d3f3 - <unknown>!__gmp_tmp_reentrant_free
5: 0x9e6e3 - <unknown>!__gmpn_gcdext
6: 0xa1dcd - <unknown>!__gmpz_gcdext
7: 0xa2bad - <unknown>!__gmpz_invert
8: 0xa941f - <unknown>!integer_gmp_invert
9: 0xaa4cb - <unknown>!_blk_c1yM
10: 0x4ab2f - <unknown>!StgRun
11: 0x2a60c - <unknown>!scheduleWaitThread
12: 0xa233 - <unknown>!rts_evalLazyIO
13: 0xa362 - <unknown>!hs_main
14: 0x6ec1 - <unknown>!main
15: 0x17ad12 - <unknown>!__main_void
16: 0x17ad84 - <unknown>!_start
note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
2: wasm trap: wasm `unreachable` instruction executed
However, if either -Oz is changed to -Os (or -O3 and other optimization levels), or if -Xclang -target-abi -Xclang experimental-mv, then it compiles and runs fine, producing the correct result 7690788370462822410877571751743509720259.