Hi!
We already have __builtin_bswap{16,32,64,128}, the last one has been
added ~6 years ago. So, I think we should have also
__builtin_bitreverse128.
The following patch does that.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Note, we don't have __builtin_bswapg and I don't think we should, one can
only byteswap something which has number of bits divisible by CHAR_BIT.
For __builtin_bitreverseg that isn't a problem, but am not sure I want to
spend time handling it on say unsigned _BitInt(357). Perhaps only if there
is some real-world use-case.
2026-05-16 Jakub Jelinek <[email protected]>
PR target/50481
* doc/extend.texi (__builtin_bitreverse32, __builtin_bitreverse64):
Tweak wording for consistency with __builtin_bswap*.
(__builtin_bitreverse128): Document.
* builtins.def (BUILT_IN_BITREVERSE128): New.
* builtins.cc (expand_builtin): Handle also BUILT_IN_BITREVERSE128.
(is_inexpensive_builtin): Likewise.
* fold-const-call.cc (fold_const_call_ss): Handle also
CFN_BUILT_IN_BITREVERSE128.
* fold-const.cc (tree_call_nonnegative_warnv_p): Likewise.
* tree-ssa-ccp.cc (evaluate_stmt): Handle also BUILT_IN_BITREVERSE128.
* tree-ssa-phiopt.cc (empty_bb_or_one_feeding_into_p): Handle also
CFN_BUILT_IN_BITREVERSE128.
(cond_removal_in_builtin_zero_pattern): Likewise.
* gcc.dg/builtin-bitreverse-1.c: Add __builtin_bitreverse128 tests.
* gcc.dg/builtin-bitreverse-2.c: Likewise.
--- gcc/doc/extend.texi.jj 2026-05-15 09:31:18.380852668 +0200
+++ gcc/doc/extend.texi 2026-05-15 11:41:31.441911030 +0200
@@ -16032,15 +16032,20 @@ are 16-bit.
@enddefbuiltin
@defbuiltin{uint32_t __builtin_bitreverse32 (uint32_t @var{x})}
-Similar to @code{__builtin_bitreverse8}, except the argument and return types
+Similar to @code{__builtin_bitreverse16}, except the argument and return types
are 32-bit.
@enddefbuiltin
@defbuiltin{uint64_t __builtin_bitreverse64 (uint64_t @var{x})}
-Similar to @code{__builtin_bitreverse8}, except the argument and return types
+Similar to @code{__builtin_bitreverse32}, except the argument and return types
are 64-bit.
@enddefbuiltin
+@defbuiltin{uint128_t __builtin_bitreverse128 (uint128_t @var{x})}
+Similar to @code{__builtin_bitreverse64}, except the argument and return types
+are 128-bit. Only supported on targets when 128-bit types are supported.
+@enddefbuiltin
+
@node CRC Builtins
@subsection CRC Builtins
@cindex CRC builtins
--- gcc/builtins.def.jj 2026-05-15 09:31:18.379183958 +0200
+++ gcc/builtins.def 2026-05-15 11:00:08.850492644 +0200
@@ -1028,6 +1028,7 @@ DEF_GCC_BUILTIN (BUILT_IN_BITREVE
DEF_GCC_BUILTIN (BUILT_IN_BITREVERSE16, "bitreverse16",
BT_FN_UINT16_UINT16, ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN (BUILT_IN_BITREVERSE32, "bitreverse32",
BT_FN_UINT32_UINT32, ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_GCC_BUILTIN (BUILT_IN_BITREVERSE64, "bitreverse64",
BT_FN_UINT64_UINT64, ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN (BUILT_IN_BITREVERSE128, "bitreverse128",
BT_FN_UINT128_UINT128, ATTR_CONST_NOTHROW_LEAF_LIST)
DEF_EXT_LIB_BUILTIN (BUILT_IN_CLEAR_CACHE, "__clear_cache",
BT_FN_VOID_PTR_PTR, ATTR_NOTHROW_LEAF_LIST)
/* [trans-mem]: Adjust BUILT_IN_TM_CALLOC if BUILT_IN_CALLOC is changed. */
--- gcc/builtins.cc.jj 2026-05-15 09:31:18.378534258 +0200
+++ gcc/builtins.cc 2026-05-15 11:01:20.014275990 +0200
@@ -8188,6 +8188,7 @@ expand_builtin (tree exp, rtx target, rt
case BUILT_IN_BITREVERSE16:
case BUILT_IN_BITREVERSE32:
case BUILT_IN_BITREVERSE64:
+ case BUILT_IN_BITREVERSE128:
target = expand_builtin_unop (target_mode, exp, target, subtarget,
bitreverse_optab);
if (target)
@@ -12357,6 +12358,7 @@ is_inexpensive_builtin (tree decl)
case BUILT_IN_BITREVERSE16:
case BUILT_IN_BITREVERSE32:
case BUILT_IN_BITREVERSE64:
+ case BUILT_IN_BITREVERSE128:
case BUILT_IN_CLZ:
case BUILT_IN_CLZIMAX:
case BUILT_IN_CLZL:
--- gcc/fold-const-call.cc.jj 2026-05-15 09:31:18.381940011 +0200
+++ gcc/fold-const-call.cc 2026-05-15 11:01:35.660008503 +0200
@@ -1106,6 +1106,7 @@ fold_const_call_ss (wide_int *result, co
case CFN_BUILT_IN_BITREVERSE16:
case CFN_BUILT_IN_BITREVERSE32:
case CFN_BUILT_IN_BITREVERSE64:
+ case CFN_BUILT_IN_BITREVERSE128:
*result = wi::bitreverse (wide_int::from (arg, precision,
TYPE_SIGN (arg_type)));
return true;
--- gcc/fold-const.cc.jj 2026-05-15 09:31:18.382677943 +0200
+++ gcc/fold-const.cc 2026-05-15 11:01:51.075744951 +0200
@@ -14988,6 +14988,7 @@ tree_call_nonnegative_warnv_p (tree type
case CFN_BUILT_IN_BITREVERSE16:
case CFN_BUILT_IN_BITREVERSE32:
case CFN_BUILT_IN_BITREVERSE64:
+ case CFN_BUILT_IN_BITREVERSE128:
/* Always true. */
return true;
--- gcc/tree-ssa-ccp.cc.jj 2026-05-15 09:31:18.384503870 +0200
+++ gcc/tree-ssa-ccp.cc 2026-05-15 22:27:05.533474689 +0200
@@ -2466,6 +2466,7 @@ evaluate_stmt (gimple *stmt)
case BUILT_IN_BITREVERSE16:
case BUILT_IN_BITREVERSE32:
case BUILT_IN_BITREVERSE64:
+ case BUILT_IN_BITREVERSE128:
val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
if (val.lattice_val == UNDEFINED)
break;
--- gcc/tree-ssa-phiopt.cc.jj 2026-05-15 09:31:18.384795813 +0200
+++ gcc/tree-ssa-phiopt.cc 2026-05-15 11:08:28.023938328 +0200
@@ -823,6 +823,7 @@ empty_bb_or_one_feeding_into_p (basic_bl
case CFN_BUILT_IN_BITREVERSE16:
case CFN_BUILT_IN_BITREVERSE32:
case CFN_BUILT_IN_BITREVERSE64:
+ case CFN_BUILT_IN_BITREVERSE128:
CASE_CFN_FFS:
CASE_CFN_PARITY:
CASE_CFN_POPCOUNT:
@@ -2586,6 +2587,7 @@ cond_removal_in_builtin_zero_pattern (ba
case CFN_BUILT_IN_BITREVERSE16:
case CFN_BUILT_IN_BITREVERSE32:
case CFN_BUILT_IN_BITREVERSE64:
+ case CFN_BUILT_IN_BITREVERSE128:
CASE_CFN_FFS:
CASE_CFN_PARITY:
CASE_CFN_POPCOUNT:
--- gcc/testsuite/gcc.dg/builtin-bitreverse-1.c.jj 2026-05-15
09:47:01.332664414 +0200
+++ gcc/testsuite/gcc.dg/builtin-bitreverse-1.c 2026-05-15 11:46:42.888574660
+0200
@@ -25,6 +25,14 @@ br64 (unsigned long long x)
return __builtin_bitreverse64 (x);
}
+#if __SIZEOF_INT128__ == 16
+[[gnu::noipa]] static unsigned __int128
+br128 (unsigned __int128 x)
+{
+ return __builtin_bitreverse128 (x);
+}
+#endif
+
int
main ()
{
@@ -67,5 +75,18 @@ main ()
if (br64 (0xffffffffffffffffull) != 0xffffffffffffffffull)
__builtin_abort ();
#endif
+#if __SIZEOF_INT128__ == 16
+ if (br128 (0) != 0)
+ __builtin_abort ();
+ if (br128 (1) != (unsigned __int128) 1 << 127)
+ __builtin_abort ();
+ if (br128 (((unsigned __int128) 0x0123456789abcdefull << 64)
+ | 0x2468ace013579bdfull)
+ != (((unsigned __int128) 0xfbd9eac807351624ull << 64)
+ | 0xf7b3d591e6a2c480ull))
+ __builtin_abort ();
+ if (br128 (~(unsigned __int128) 0) != ~(unsigned __int128) 0)
+ __builtin_abort ();
+#endif
#endif
}
--- gcc/testsuite/gcc.dg/builtin-bitreverse-2.c.jj 2026-05-15
09:36:13.907780008 +0200
+++ gcc/testsuite/gcc.dg/builtin-bitreverse-2.c 2026-05-15 11:46:55.306361889
+0200
@@ -12,6 +12,13 @@ _Static_assert (__builtin_bitreverse32 (
#endif
#if __SIZEOF_LONG_LONG__ == 8
_Static_assert (__builtin_bitreverse64 (0x0123456789abcdefull)
- == 0xf7b3d591e6a2c480ull, "bitreverse64");
+ == 0xf7b3d591e6a2c480ull, "bitreverse64");
+#endif
+#if __SIZEOF_INT128__ == 16
+_Static_assert (__builtin_bitreverse128 (((unsigned __int128)
+ 0x0123456789abcdefull << 64)
+ | 0x2468ace013579bdfull)
+ == (((unsigned __int128) 0xfbd9eac807351624ull << 64)
+ | 0xf7b3d591e6a2c480ull), "bitreverse128");
#endif
#endif
Jakub
