[llvm-bugs] [Bug 31305] New: Incorrect code generated for llvm.masked.store <2 x i1> with a variable mask

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31305

            Bug ID: 31305
           Summary: Incorrect code generated for llvm.masked.store <2 x
                    i1> with a variable mask
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: zvi.rackover at intel.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

define void @unmasked(<2 x i1> %x, <2 x i1>* %ptr) nounwind {
   store <2 x i1> %x, <2 x i1>* %ptr
   ret void
 }

 define void @masked_const(<2 x i1> %x, <2 x i1>* %ptr) nounwind {
   call void @llvm.masked.store.v2i1.p0v2i1(<2 x i1> %x, <2 x i1>* %ptr, i32 0,
<2 x i1> <i1 1, i1 1>)
   ret void
 }


For both functions above we generate:
llc -mcpu=skx

  vpsllq  $63, %xmm0, %xmm0
  vptestmq        %xmm0, %xmm0, %k0
  kmovb   %k0, (%rdi)
  retq

But in the case of a variable mask:

 define void @masked_var(<2 x i1> %x, <2 x i1>* %ptr) nounwind {
   call void @llvm.masked.store.v2i1.p0v2i1(<2 x i1> %x, <2 x i1>* %ptr, i32 0,
<2 x i1> %x)
   ret void
 }

the generated code stores each vector element in a distinct byte:
        vpsllq  $63, %xmm0, %xmm0
        vptestmq        %xmm0, %xmm0, %k0
        kshiftlw        $15, %k0, %k1
        kshiftrw        $15, %k1, %k1
        kmovw   %k1, %eax
        andl    $1, %eax
        testb   %al, %al
        je      .LBB2_2
# BB#1:                                 # %cond.store
        kmovb   %k1, (%rdi)
.LBB2_2:                                # %else
        kshiftlw        $14, %k0, %k0
        kshiftrw        $15, %k0, %k0
        kmovw   %k0, %eax
        andl    $1, %eax
        testb   %al, %al
        je      .LBB2_4
# BB#3:                                 # %cond.store1
        kmovb   %k0, 1(%rdi)
.LBB2_4:                                # %else2
        retq

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