[llvm-bugs] [Bug 43453] New: Incorrect code generated with ext_vector_type(16)

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Sep 25 13:32:03 PDT 2019


            Bug ID: 43453
           Summary: Incorrect code generated with ext_vector_type(16)
           Product: clang
           Version: 9.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: warp at iki.fi
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Consider the following code:

typedef double Double16 __attribute__((ext_vector_type(16)));
// or
// typedef double Double16 __attribute__((vector_size(8*16)));

Double16 mult(const Double16& v1, const Double16& v2)
    return v1 * v2;

When compiling with clang 9.0.0 using -Ofast -march=skylake, the following
result is produced:

        vmovapd ymm0, ymmword ptr [rsi]
        vmovapd ymm1, ymmword ptr [rsi + 32]
        vmovapd ymm2, ymmword ptr [rsi + 64]
        vmovapd ymm3, ymmword ptr [rsi + 96]
        vmulpd  ymm0, ymm0, ymmword ptr [rdi]
        vmulpd  ymm1, ymm1, ymmword ptr [rdi + 32]
        vmulpd  ymm2, ymm2, ymmword ptr [rdi + 64]
        vmulpd  ymm3, ymm3, ymmword ptr [rdi + 96]

I believe this is erroneous, as the result is not stored into the function
return value according to the ABI.

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