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Avoid __builtin_ctzll on some platforms #604

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Aug 3, 2023
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Avoid __builtin_ctzll on some platforms #604

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40 changes: 32 additions & 8 deletions cbits/is-valid-utf8.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ SUCH DAMAGE.
#endif

#include <MachDeps.h>
#include "Rts.h"
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@juhp juhp Aug 8, 2023 •
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This seems to break x86_64 on Fedora for me... booting 9.4.6 with either 9.2.8 or 9.4.5:

In file included from /usr/lib64/ghc-9.4.5/lib/x86_64-linux-ghc-9.4.5/rts-1.0.2/include/Rts.h:235,
                 from libraries/bytestring/cbits/is-valid-utf8.c:53:0: error:
    
/usr/lib64/ghc-9.4.5/lib/x86_64-linux-ghc-9.4.5/rts-1.0.2/include/rts/OSThreads.h:38:5: error:
     error: unknown type name ‘clockid_t’
       38 |     clockid_t timeout_clk;
          |     ^~~~~~~~~
   |
38 |     clockid_t timeout_clk;
   |     ^

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Looks to me like that #include should be conditional somehow.


#ifdef WORDS_BIGENDIAN
#define to_little_endian(x) __builtin_bswap64(x)
Expand All @@ -66,6 +67,29 @@ static inline uint64_t read_uint64(const uint64_t *p) {
return r;
}

// stand-in for __builtin_ctzll, used because __builtin_ctzll can
// cause runtime linker issues for GHC in some exotic situations (#601)
//
// See also these ghc issues:
// * https://gitlab.haskell.org/ghc/ghc/-/issues/21787
// * https://gitlab.haskell.org/ghc/ghc/-/issues/22011
static inline int hs_bytestring_ctz64(const uint64_t x) {
// These CPP conditions are taken from ghc-prim:
// https://gitlab.haskell.org/ghc/ghc/-/blob/73b5c7ce33929e1f7c9283ed7c2860aa40f6d0ec/libraries/ghc-prim/cbits/ctz.c#L31-57
// credit to Herbert Valerio Riedel, Erik de Castro Lopo
#if defined(__GNUC__) && (defined(i386_HOST_ARCH) || defined(powerpc_HOST_ARCH))
uint32_t xhi = (uint32_t)(x >> 32);
uint32_t xlo = (uint32_t) x;
return xlo ? __builtin_ctz(xlo) : 32 + __builtin_ctz(xhi);
#elif SIZEOF_UNSIGNED_LONG == 8
return __builtin_ctzl(x);
#elif SIZEOF_UNSIGNED_LONG_LONG == 8
return __builtin_ctzll(x);
#else
# error no suitable __builtin_ctz() found
#endif
}

static inline int is_valid_utf8_fallback(uint8_t const *const src,
size_t const len) {
uint8_t const *ptr = (uint8_t const *)src;
Expand Down Expand Up @@ -100,16 +124,16 @@ static inline int is_valid_utf8_fallback(uint8_t const *const src,
if (results[3] == 0) {
ptr += 8;
} else {
ptr += (__builtin_ctzll(results[3]) / 8);
ptr += (hs_bytestring_ctz64(results[3]) / 8);
}
} else {
ptr += (__builtin_ctzll(results[2]) / 8);
ptr += (hs_bytestring_ctz64(results[2]) / 8);
}
} else {
ptr += (__builtin_ctzll(results[1]) / 8);
ptr += (hs_bytestring_ctz64(results[1]) / 8);
}
} else {
ptr += (__builtin_ctzll(results[0]) / 8);
ptr += (hs_bytestring_ctz64(results[0]) / 8);
}
}
}
Expand Down Expand Up @@ -207,16 +231,16 @@ static inline int is_valid_utf8_sse2(uint8_t const *const src,
if (result == 0) {
ptr += 16;
} else {
ptr += __builtin_ctzll(result);
ptr += __builtin_ctz(result);
}
} else {
ptr += __builtin_ctzll(result);
ptr += __builtin_ctz(result);
}
} else {
ptr += __builtin_ctzll(result);
ptr += __builtin_ctz(result);
}
} else {
ptr += __builtin_ctzll(result);
ptr += __builtin_ctz(result);
}
}
}
Expand Down
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