[Bug c++/105353] New: __builtin_shufflevector with template parameter fails to compile on GCC 12 but compiles on clang
john_platts at hotmail dot com
gcc-bugzilla@gcc.gnu.org
Fri Apr 22 21:07:58 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105353
Bug ID: 105353
Summary: __builtin_shufflevector with template parameter fails
to compile on GCC 12 but compiles on clang
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: john_platts at hotmail dot com
Target Milestone: ---
The following code fails to compile with GCC 12 but compiles successfully on
clang (with the -std=c++17 flag):
#include <cstdint>
typedef std::uint8_t Simd128U8VectT __attribute__((__vector_size__(16)));
template<int ShuffleIndex>
static inline Simd128U8VectT ShufFunc(Simd128U8VectT vect) noexcept {
if constexpr(unsigned(ShuffleIndex) >= 16)
return Simd128U8VectT { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
else if constexpr(ShuffleIndex == 0)
return vect;
else
return __builtin_shufflevector(vect, vect, ShuffleIndex, ShuffleIndex +
1,
ShuffleIndex + 2, ShuffleIndex + 3, ShuffleIndex + 4, ShuffleIndex
+ 5,
ShuffleIndex + 6, ShuffleIndex + 7, ShuffleIndex + 8, ShuffleIndex
+ 9,
ShuffleIndex + 10, ShuffleIndex + 11, ShuffleIndex + 12,
ShuffleIndex + 13,
ShuffleIndex + 14, ShuffleIndex + 15);
}
auto func1(Simd128U8VectT vect) noexcept {
return ShufFunc<5>(vect);
}
Here is the assembly output when the above code is compiled on clang 14.0.0
with the -O2 -std=c++17 flags:
func1(unsigned char __vector(16)): # @func1(unsigned
char __vector(16))
movdqa xmm1, xmm0
psrldq xmm1, 5 # xmm1 =
xmm1[5,6,7,8,9,10,11,12,13,14,15],zero,zero,zero,zero,zero
pslldq xmm0, 11 # xmm0 =
zero,zero,zero,zero,zero,zero,zero,zero,zero,zero,zero,xmm0[0,1,2,3,4]
por xmm0, xmm1
ret
The below code compiles successfully with GCC 11 and GCC 12 (which uses
__builtin_shuffle instead of __builtin_shufflevector):
#include <cstdint>
typedef std::uint8_t Simd128U8VectT __attribute__((__vector_size__(16)));
template<int ShuffleIndex>
static inline Simd128U8VectT ShufFunc(Simd128U8VectT vect) noexcept {
if constexpr(unsigned(ShuffleIndex) >= 16)
return Simd128U8VectT { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
else if constexpr(ShuffleIndex == 0)
return vect;
else
return __builtin_shuffle(vect, vect, (Simd128U8VectT){
ShuffleIndex, ShuffleIndex + 1,
ShuffleIndex + 2, ShuffleIndex + 3, ShuffleIndex + 4, ShuffleIndex
+ 5,
ShuffleIndex + 6, ShuffleIndex + 7, ShuffleIndex + 8, ShuffleIndex
+ 9,
ShuffleIndex + 10, ShuffleIndex + 11, ShuffleIndex + 12,
ShuffleIndex + 13,
ShuffleIndex + 14, ShuffleIndex + 15 });
}
auto func1(Simd128U8VectT vect) noexcept {
return ShufFunc<5>(vect);
}
More information about the Gcc-bugs
mailing list