[llvm] [AggressiveInstCombine] Improve popcount matching if the input has known zero bits (PR #142501)

[Craig Topper via llvm-commits]

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@@ -191,3 +191,51 @@ define <4 x i32> @popcount32vec(<4 x i32> %0) {
   %13 = lshr <4 x i32> %12, <i32 24, i32 24, i32 24, i32 24>
   ret <4 x i32> %13
 }
+
+define signext i32 @popcount64_zext(i32 %x) {
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topperc wrote:

That's also present on the other scalar tests in this file. Should we remove it?

https://github.com/llvm/llvm-project/pull/142501