InlineCostAnnotationPrinterPass - print constants to which instructions are simplified

[knaumov]

Summary

Adding functionality to InlineCostAnnotationPrinterPass to print the constant (if any) to which each instruction will be simplified. This feature helps for debugging purposes to track the constant folding thread in InlineCost Analysis.

[knaumov]

ping

[mtrofin]

lgtm

llvm/lib/Analysis/InlineCost.cpp

CallAnalyzer(
       ProfileSummaryInfo *PSI = nullptr,
       OptimizationRemarkEmitter *ORE = nullptr)
       : TTI(TTI), GetAssumptionCache(GetAssumptionCache), GetBFI(GetBFI),
         PSI(PSI), F(Callee), DL(F.getParent()->getDataLayout()), ORE(ORE),
         CandidateCall(Call), EnableLoadElimination(true) {}
 
   InlineResult analyze();
 
+  Optional<Constant*> getSimplifiedValue(Instruction *I) {
+    if (SimplifiedValues.find(I) != SimplifiedValues.end())
+      return SimplifiedValues[I];
+    return None;
+  }
+
   // Keep a bunch of stats about the cost savings found so we can print them
   // out when debugging.
   unsigned NumConstantArgs = 0;
   unsigned NumConstantOffsetPtrArgs = 0;
   unsigned NumAllocaArgs = 0;
   unsigned NumConstantPtrCmps = 0;
   unsigned NumConstantPtrDiffs = 0;
   unsigned NumInstructionsSimplified = 0;
else {
     OS << "; cost before = " << Record->CostBefore
        << ", cost after = " << Record->CostAfter
        << ", threshold before = " << Record->ThresholdBefore
        << ", threshold after = " << Record->ThresholdAfter << ", ";
     OS << "cost delta = " << Record->getCostDelta();
     if (Record->hasThresholdChanged())
       OS << ", threshold delta = " << Record->getThresholdDelta();
   }
+  auto C = ICCA->getSimplifiedValue(const_cast<Instruction *>(I));
+  if (C) {
+    OS << ", simplified to ";
+    C.getValue()->print(OS, true);
+  }
   OS << "\n";
 }
 
 /// If 'V' maps to a SROA candidate, disable SROA for it.
 void CallAnalyzer::disableSROA(Value *V) {
   if (auto *SROAArg = getSROAArgForValueOrNull(V)) {
     disableSROAForArg(SROAArg);
   }
for (Instruction &I : BB) {
         ICCA.analyze();
         OS << "      Analyzing call of " << CalledFunction->getName()
            << "... (caller:" << CI->getCaller()->getName() << ")\n";
         ICCA.dump();
       }
     }
   }
   return PreservedAnalyses::all();
-}
+}
 

llvm/test/Transforms/Inline/simplified_to.ll

+; RUN: opt < %s -passes="print<inline-cost>" 2>&1 | FileCheck %s
+
+; CHECK-LABEL: @test()
+; CHECK: cost before = {{.*}}, cost after = {{.*}}, threshold before = {{.*}}, threshold after = {{.*}}, cost delta = {{.*}}, simplified to i1 false
+; CHECK:   %1 = icmp eq i32 4, 5
+
+define i32 @test() {
+  %1 = icmp eq i32 4, 5
+  ret i32 0
+}
+
+define void @main() {
+  %1 = call i32 @test()
+  ret void
+}