[llvm] [SelectionDAG] Preserve CTTZ_ELTS lane count during expansion (PR #217982)

[Simon Pilgrim via llvm-commits]

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@@ -101,5 +102,25 @@ define i8 @ctz_v8i16_poison(<8 x i16> %a) {
   ret i8 %res
 }
 
+define i32 @ctz_zero_v4i1() {
+; CHECK-LABEL: ctz_zero_v4i1:
+; CHECK:         movl $4, %eax
+; CHECK-NEXT:    retq
+; AVX512-LABEL: ctz_zero_v4i1:
+; AVX512:         addb $5, %al
+  %res = call i32 @llvm.experimental.cttz.elts.i32.v4i1(<4 x i1> zeroinitializer, i1 false)
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RKSimon wrote:

still not great - use the update script to regenerate ALL the codegen checks - then manually restore the constant pool entries in the earlier tests (and make sure you remove the NOTE the update script will add to the top of the file)

https://github.com/llvm/llvm-project/pull/217982