[llvm-bugs] [Bug 52351] New: [InstCombine] try harder to peek through vector bitcasts with bitwise logic

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52351

            Bug ID: 52351
           Summary: [InstCombine] try harder to peek through vector
                    bitcasts with bitwise logic
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: spatel+llvm at rotateright.com
                CC: llvm-bugs at lists.llvm.org

Vector bitcasts can interfere with bitwise logic reductions:

define <2 x i64> @src(<2 x i64> %x, <4 x i32> %y, <4 x i32> %z) {
  %yb = bitcast <4 x i32> %y to <2 x i64>
  %yz = and <4 x i32> %z, %y
  %yzb = bitcast <4 x i32> %yz to <2 x i64>
  %xy = and <2 x i64> %yb, %x
  %r = or <2 x i64> %xy, %yzb
  ret <2 x i64> %r
}

define <2 x i64> @tgt(<2 x i64> %x, <4 x i32> %y, <4 x i32> %z)  {
  %xb = bitcast <2 x i64> %x to <4 x i32>
  %xz = or <4 x i32> %xb, %z
  %xyz = and <4 x i32> %xz, %y
  %r = bitcast <4 x i32> %xyz to <2 x i64>
  ret <2 x i64> %r
}

https://alive2.llvm.org/ce/z/dWQbwD

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