[llvm] [InstCombine] Drop redundant dereferenceable assumptions (PR #202946)

[Nikita Popov via llvm-commits]

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@@ -1257,6 +1257,23 @@ define void @assume_dereferenceable_variable_on_nullptr(i64 %count) {
   ret void
 }
 
+define void @redundant_assume_dereferenceable_2(ptr dereferenceable(2) %ptr) {
+; CHECK-LABEL: @redundant_assume_dereferenceable_2(
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %ptr, i64 2) ]
+  ret void
+}
+
+define void @not_redundant_assume_dereferenceable_2(ptr dereferenceable(1) %ptr) {
+; CHECK-LABEL: @not_redundant_assume_dereferenceable_2(
+; CHECK-NEXT:    call void @llvm.assume(i1 true) [ "dereferenceable"(ptr [[PTR:%.*]], i64 2) ]
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.assume(i1 true) [ "dereferenceable"(ptr %ptr, i64 2) ]
+  ret void
+}
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nikic wrote:

Can you also add a test with two assumes, where one is redundant?

https://github.com/llvm/llvm-project/pull/202946