[llvm] [InstCombine] Remove over-generalization from computeKnownBitsFromCmp() (PR #72637)

[Nikita Popov via llvm-commits]

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@@ -4016,9 +4016,10 @@ define i32 @abs_preserve(i32 %x) {
 declare void @llvm.assume(i1)
 define i1 @PR35794(ptr %a) {
 ; CHECK-LABEL: @PR35794(
-; CHECK-NEXT:    [[MASKCOND:%.*]] = icmp eq ptr [[A:%.*]], null
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt ptr [[A:%.*]], inttoptr (i64 -1 to ptr)
+; CHECK-NEXT:    [[MASKCOND:%.*]] = icmp eq ptr [[A]], null
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nikic wrote:

This is no longer handled just because `m_APInt()` doesn't match pointers. I could add a special case just for this and retain the behavior.

https://github.com/llvm/llvm-project/pull/72637