Kill the benefit check in findCands, let the cost model filters out t…

…he root (#694)

lib/Inst/Inst.cpp

@@ -1052,18 +1052,15 @@ void souper::findCands(Inst *Root, std::vector<Inst *> &Guesses,
                bool WidthMustMatch, bool FilterVars, int Max) {
   // breadth-first search
   std::set<Inst *> Visited;
-  std::queue<std::tuple<Inst *,int>> Q;
-  Q.push(std::make_tuple(Root, 0));
+  std::queue<Inst *> Q;
+  Q.push(Root);
   while (!Q.empty()) {
-    Inst *I;
-    int Benefit;
-    std::tie(I, Benefit) = Q.front();
+    Inst *I = Q.front();
     Q.pop();
-    ++Benefit;
     if (Visited.insert(I).second) {
       for (auto Op : I->Ops)
-        Q.push(std::make_tuple(Op, Benefit));
-      if (Benefit > 1 && I->Available && I->K != Inst::Const
+        Q.push(Op);
+      if (I->Available && I->K != Inst::Const
           && I->K != Inst::UntypedConst) {
         if (WidthMustMatch && I->Width != Root->Width)
           continue;

test/Infer/root-ignore-cost.opt

@@ -0,0 +1,8 @@
+; REQUIRES: solver, synthesis
+; RUN: %souper-check -infer-rhs -souper-enumerative-synthesis -souper-enumerative-synthesis-num-instructions=3 -souper-enumerative-synthesis-ignore-cost %solver %s > %t1
+; RUN: %FileCheck %s < %t1
+
+; CHECK: result %0
+
+%0:i8 = var
+infer %0

test/Infer/root-with-cost.opt

@@ -0,0 +1,10 @@
+; REQUIRES: solver, synthesis
+; RUN: %souper-check -infer-rhs -souper-enumerative-synthesis -souper-enumerative-synthesis-num-instructions=3 %solver %s > %t1
+; RUN: %souper-check -infer-rhs -souper-enumerative-synthesis %solver %s > %t2
+; RUN: %FileCheck %s < %t1
+; RUN: %FileCheck %s < %t2
+
+; CHECK: ; Failed to infer RHS
+
+%0:i32 = var
+infer %0