[llvm-reduce] Actually skip invalid candidates in operands-to-args

This was checked while counting but not actually when doing the reduction, resulting in crashes.

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D112766

llvm/test/tools/llvm-reduce/operands-to-args.ll

@@ -54,3 +54,19 @@ entry:
   ret void
 }
 
+
+; Make sure to skip functions with non-direct call users
+declare void @e(i8*)
+
+; INTERESTING-LABEL: define void @g() {
+define void @g() {
+  call void @e(i8* bitcast (void (i8**)* @f to i8*))
+  ret void
+}
+
+; INTERESTING-LABEL: define void @f(i8** %a) {
+define void @f(i8** %a) {
+  %1 = load i8*, i8** %a
+  %2 = bitcast i8* %1 to i32*
+  ret void
+}

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

@@ -174,6 +174,8 @@ static void substituteOperandWithArgument(Function *OldF,
 static void reduceOperandsToArgs(Oracle &O, Module &Program) {
   SmallVector<Use *> OperandsToReduce;
   for (Function &F : make_early_inc_range(Program.functions())) {
+    if (!canReplaceFunction(&F))
+      continue;
     OperandsToReduce.clear();
     for (Instruction &I : instructions(&F)) {
       for (Use &Op : I.operands()) {