[llvm-bugs] [Bug 47494] New: [IR] Suboptimal vector code

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47494

            Bug ID: 47494
           Summary: [IR] Suboptimal vector code
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: david.bolvansky at gmail.com
                CC: llvm-bugs at lists.llvm.org

void test(int* restrict r, int* restrict a){
    for (int i = 0; i < 16; i++){

         r[i] +=  r[i+1];
    }
}

Clang -O3 -mavx2:
test:                                   # @test
        vmovdqu ymm0, ymmword ptr [rdi]
        vmovdqu ymm1, ymmword ptr [rdi + 32]
        vperm2i128      ymm2, ymm0, ymm1, 33    # ymm2 = ymm0[2,3],ymm1[0,1]
        vpalignr        ymm2, ymm2, ymm0, 4             # ymm2 =
ymm0[4,5,6,7,8,9,10,11,12,13,14,15],ymm2[0,1,2,3],ymm0[20,21,22,23,24,25,26,27,28,29,30,31],ymm2[16,17,18,19]
        vpaddd  ymm0, ymm0, ymm2
        vmovdqu ymmword ptr [rdi], ymm0
        vmovdqu xmm0, xmmword ptr [rdi + 48]
        vpshufd xmm2, xmm0, 249                 # xmm2 = xmm0[1,2,3,3]
        vpinsrd xmm2, xmm2, dword ptr [rdi + 64], 3
        vpalignr        xmm0, xmm0, xmmword ptr [rdi + 32], 4 # xmm0 =
mem[4,5,6,7,8,9,10,11,12,13,14,15],xmm0[0,1,2,3]
        vinserti128     ymm0, ymm0, xmm2, 1
        vpaddd  ymm0, ymm1, ymm0
        vmovdqu ymmword ptr [rdi + 32], ymm0
        vzeroupper
        ret


ICC -O3 -mavx2:
test:
        vmovdqu   ymm0, YMMWORD PTR [rdi]                       #4.10
        vmovdqu   ymm2, YMMWORD PTR [32+rdi]                    #4.10
        vpaddd    ymm1, ymm0, YMMWORD PTR [4+rdi]               #4.10
        vpaddd    ymm3, ymm2, YMMWORD PTR [36+rdi]              #4.10
        vmovdqu   YMMWORD PTR [rdi], ymm1                       #4.10
        vmovdqu   YMMWORD PTR [32+rdi], ymm3                    #4.10
        vzeroupper                                              #6.1
        ret                                                     #6.1

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