[llvm-bugs] [Bug 39016] New: [DAGCombine] Missed extractelement(bitcast(scalar_to_vector()) combine

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39016

            Bug ID: 39016
           Summary: [DAGCombine] Missed
                    extractelement(bitcast(scalar_to_vector()) combine
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: llvm-bugs at lists.llvm.org, spatel+llvm at rotateright.com

define i32 @test(i64 %a0) {
  %1 = insertelement <2 x i64> zeroinitializer, i64 %a0, i32 0
  %2 = bitcast <2 x i64> %1 to <4 x i32>
  %3 = extractelement <4 x i32> %2, i32 0
  ret i32 %3
}

llc -mtriple=x86_64-unknown

test: # @test
  movq %rdi, %xmm0
  movd %xmm0, %eax
  retq

This could be reduced to:

test: # @test
  mov %edi, %eax
  retq

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