[LoongArch][Clang] Make the parameters and return value of {x,}vshuf.b builtins signed char vectors (#114512)

The lsxintrin.h and and lasxintrin.h headers uses `signed char` vectors
instead of `unsigned char` vectors.  GCC also uses `signed char` for
them, so align their definition with the headers and GCC.

Depends on #114511.  Part of #110834 fix.

Author: xry111

clang/include/clang/Basic/BuiltinsLoongArchLASX.def

@@ -935,7 +935,7 @@ TARGET_BUILTIN(__builtin_lasx_xvilvh_h, "V16sV16sV16s", "nc", "lasx")
 TARGET_BUILTIN(__builtin_lasx_xvilvh_w, "V8iV8iV8i", "nc", "lasx")
 TARGET_BUILTIN(__builtin_lasx_xvilvh_d, "V4LLiV4LLiV4LLi", "nc", "lasx")
 
-TARGET_BUILTIN(__builtin_lasx_xvshuf_b, "V32UcV32UcV32UcV32Uc", "nc", "lasx")
+TARGET_BUILTIN(__builtin_lasx_xvshuf_b, "V32ScV32ScV32ScV32Sc", "nc", "lasx")
 
 TARGET_BUILTIN(__builtin_lasx_xvshuf_h, "V16sV16sV16sV16s", "nc", "lasx")
 TARGET_BUILTIN(__builtin_lasx_xvshuf_w, "V8iV8iV8iV8i", "nc", "lasx")

clang/include/clang/Basic/BuiltinsLoongArchLSX.def

@@ -910,7 +910,7 @@ TARGET_BUILTIN(__builtin_lsx_vilvh_h, "V8sV8sV8s", "nc", "lsx")
 TARGET_BUILTIN(__builtin_lsx_vilvh_w, "V4iV4iV4i", "nc", "lsx")
 TARGET_BUILTIN(__builtin_lsx_vilvh_d, "V2LLiV2LLiV2LLi", "nc", "lsx")
 
-TARGET_BUILTIN(__builtin_lsx_vshuf_b, "V16UcV16UcV16UcV16Uc", "nc", "lsx")
+TARGET_BUILTIN(__builtin_lsx_vshuf_b, "V16ScV16ScV16ScV16Sc", "nc", "lsx")
 
 TARGET_BUILTIN(__builtin_lsx_vshuf_h, "V8sV8sV8sV8s", "nc", "lsx")
 TARGET_BUILTIN(__builtin_lsx_vshuf_w, "V4iV4iV4iV4i", "nc", "lsx")