[Reduce] Argument reduction: do properly handle invoke insts (PR46819)

replaceFunctionCalls() is very non-exhaustive, it only handles
CallInst's. Which means, by the time we drop old function,
there may still be uses of it lurking around.
Let's instead whack-a-mole them by all by replacing with undef.

I'm not sure this is the best handling, especially for calls, but IMO
poorly reduced input is much better than crashing reduction tool.
A (previously-crashing!) test added.

Fixes https://bugs.llvm.org/show_bug.cgi?id=46819

llvm/test/Reduce/remove-invoked-functions.ll

@@ -0,0 +1,55 @@
+; RUN: llvm-reduce --test FileCheck --test-arg --check-prefixes=CHECK-ALL,CHECK-INTERESTINGNESS --test-arg %s --test-arg --input-file %s -o %t
+; RUN: cat %t | FileCheck --check-prefixes=CHECK-ALL,CHECK-FINAL %s
+
+; CHECK-INTERESTINGNESS: define i32 @maybe_throwing_callee(
+; CHECK-FINAL: define i32 @maybe_throwing_callee()
+define i32 @maybe_throwing_callee(i32 %arg) {
+; CHECK-ALL: call void @thrown()
+; CHECK-INTERESTINGNESS: ret i32
+; CHECK-FINAL: ret i32 undef
+  call void @thrown()
+  ret i32 %arg
+}
+
+; CHECK-ALL: declare void @did_not_throw(i32)
+declare void @did_not_throw(i32)
+
+; CHECK-ALL: declare void @thrown()
+declare void @thrown()
+
+; CHECK-INTERESTINGNESS: define void @caller(
+; CHECK-FINAL: define void @caller(i32 %arg)
+define void @caller(i32 %arg) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+; CHECK-ALL: bb:
+bb:
+; CHECK-INTERESTINGNESS: %i0 = invoke i32
+; CHECK-FINAL: %i0 = invoke i32 undef(i32 %arg)
+; CHECK-ALL: to label %bb3 unwind label %bb1
+  %i0 = invoke i32 @maybe_throwing_callee(i32 %arg)
+          to label %bb3 unwind label %bb1
+
+; CHECK-ALL: bb1:
+bb1:
+; CHECK-ALL: landingpad { i8*, i32 }
+; CHECK-ALL: catch i8* null
+; CHECK-ALL: call void @thrown()
+; CHECK-ALL: br label %bb4
+  landingpad { i8*, i32 }
+  catch i8* null
+  call void @thrown()
+  br label %bb4
+
+; CHECK-ALL: bb3:
+bb3:
+; CHECK-ALL: call void @did_not_throw(i32 %i0)
+; CHECK-ALL: br label %bb4
+  call void @did_not_throw(i32 %i0)
+  br label %bb4
+
+; CHECK-ALL: bb4:
+; CHECK-ALL: ret void
+bb4:
+  ret void
+}
+
+declare i32 @__gxx_personality_v0(...)

llvm/tools/llvm-reduce/deltas/ReduceArguments.cpp

@@ -94,6 +94,7 @@ static void extractArgumentsFromModule(std::vector<Chunk> ChunksToKeep,
     replaceFunctionCalls(*F, *ClonedFunc, ArgIndexesToKeep);
     // Rename Cloned Function to Old's name
     std::string FName = std::string(F->getName());
+    F->replaceAllUsesWith(UndefValue::get(F->getType()));
     F->eraseFromParent();
     ClonedFunc->setName(FName);
   }