[llvm-bugs] [Bug 50794] New: [SIMD] avgr patterns not recognized

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50794

            Bug ID: 50794
           Summary: [SIMD] avgr patterns not recognized
           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

Instead of i8x16.avgr_u and i16x8.avgr_u, these examples result in two
additions and a shift (Compiler Explorer: https://godbolt.org/z/7bKq4hTqj):


#include <wasm_simd128.h>

#pragma clang diagnostic ignored "-Wmissing-prototypes"

typedef uint8_t u8x16 __attribute__((__vector_size__(16)));
typedef uint16_t u16x8 __attribute__((__vector_size__(16)));

#if 0 // Copied from proposal

Lane-wise integer rounding average

    i8x16.avgr_u(a: v128, b: v128) -> v128
    i16x8.avgr_u(a: v128, b: v128) -> v128

Lane-wise rounding average:

def S.RoundingAverage(x, y):
    return (x + y + 1) // 2

def S.avgr_u(a, b):
    return S.lanewise_binary(S.RoundingAverage, S.AsUnsigned(a),
S.AsUnsigned(b))

#endif

u8x16 avgr8(u8x16 a, u8x16 b) {
    return (a + b + 1) >> 1;
}

u16x8 avgr16(u16x8 a, u16x8 b) {
    return (a + b + 1) >> 1;
}

u8x16 avgr8_div(u8x16 a, u8x16 b) {
    return (a + b + 1) / 2;
}

u16x8 avgr16_div(u16x8 a, u16x8 b) {
    return (a + b + 1) / 2;
}

u8x16 avgr8_intrin(u8x16 a, u8x16 b) {
    return __builtin_wasm_avgr_u_i8x16(a, b);
}

u16x8 avgr16_intrin(u16x8 a, u16x8 b) {
    return __builtin_wasm_avgr_u_i16x8(a, b);
}

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