[llvm-bugs] [Bug 50808] New: [SIMD] shuffle even/odd, extend, add should generate extadd_pairwise

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50808

            Bug ID: 50808
           Summary: [SIMD] shuffle even/odd, extend, add should generate
                    extadd_pairwise
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: WebAssembly
          Assignee: unassignedbugs at nondot.org
          Reporter: clang at evan.coeusgroup.com
                CC: llvm-bugs at lists.llvm.org

With -msimd128, shuffling to extract even and odd elements, then extending
those and adding the result should result in one of the extadd_pairwise
instructions (assuming 8 or 16 bit inputs).  It doesn't.

Right now they result in some rather atrocious code, but I filed that as
#50807.  This issue is about generating an extadd_pairwise instruction.

Example (Compiler Explorer: https://godbolt.org/z/94n6sooTs):



#include <stdint.h>

#pragma clang diagnostic ignored "-Wmissing-prototypes"

typedef   int8_t i8x16 __attribute__((__vector_size__(16)));
typedef  int16_t i16x8 __attribute__((__vector_size__(16)));
typedef  int32_t i32x4 __attribute__((__vector_size__(16)));
typedef  uint8_t u8x16 __attribute__((__vector_size__(16)));
typedef uint16_t u16x8 __attribute__((__vector_size__(16)));
typedef uint32_t u32x4 __attribute__((__vector_size__(16)));

i16x8
i8x16_extadd_pairwise(i8x16 a) {
    return (i16x8) {
      __builtin_convertvector(__builtin_shufflevector(a, a, 0, 2, 4, 6, 8, 10,
12, 14), i16x8) +
      __builtin_convertvector(__builtin_shufflevector(a, a, 1, 3, 5, 7, 9, 11,
13, 15), i16x8)  
    };
}

i32x4
i16x8_extadd_pairwise(i16x8 a) {
    return (i32x4) {
      __builtin_convertvector(__builtin_shufflevector(a, a, 0, 2, 4, 6), i32x4)
+
      __builtin_convertvector(__builtin_shufflevector(a, a, 1, 3, 5, 7), i32x4) 
    };
}

u16x8
u8x16_extadd_pairwise(i8x16 a) {
    return (u16x8) {
      __builtin_convertvector(__builtin_shufflevector(a, a, 0, 2, 4, 6, 8, 10,
12, 14), u16x8) +
      __builtin_convertvector(__builtin_shufflevector(a, a, 1, 3, 5, 7, 9, 11,
13, 15), u16x8)  
    };
}

u32x4
u16x8_extadd_pairwise(i16x8 a) {
    return (u32x4) {
      __builtin_convertvector(__builtin_shufflevector(a, a, 0, 2, 4, 6), u32x4)
+
      __builtin_convertvector(__builtin_shufflevector(a, a, 1, 3, 5, 7), u32x4) 
    };
}

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