Enrich inline messages

Summary:
This patch improves Inliner to provide causes/reasons for negative inline decisions.
1. It adds one new message field to InlineCost to report causes for Always and Never instances. All Never and Always instantiations must provide a simple message.
2. Several functions that used to return the inlining results as boolean are changed to return InlineResult which carries the cause for negative decision.
3. Changed remark priniting and debug output messages to provide the additional messages and related inline cost.
4. Adjusted tests for changed printing.

Patch by: yrouban (Yevgeny Rouban)


Reviewers: craig.topper, sammccall, sgraenitz, NutshellySima, shchenz, chandlerc, apilipenko, javed.absar, tejohnson, dblaikie, sanjoy, eraman, xbolva00

Reviewed By: tejohnson, xbolva00

Subscribers: xbolva00, llvm-commits, arsenm, mehdi_amini, eraman, haicheng, steven_wu, dexonsmith

Differential Revision: https://reviews.llvm.org/D49412

llvm-svn: 338969

1 files changed, 66 insertions, 54 deletions

diff --git a/llvm/lib/Transforms/IPO/Inliner.cpp b/llvm/lib/Transforms/IPO/Inliner.cpp
index 3da0c2e83eb..fdf47b7bd62 100644
--- a/llvm/lib/Transforms/IPO/Inliner.cpp
+++ b/llvm/lib/Transforms/IPO/Inliner.cpp
@@ -64,6 +64,7 @@
 #include <algorithm>
 #include <cassert>
 #include <functional>
+#include <sstream>
 #include <tuple>
 #include <utility>
 #include <vector>
@@ -275,8 +276,9 @@ static bool InlineCallIfPossible(
 
   // Try to inline the function.  Get the list of static allocas that were
   // inlined.
-  if (!InlineFunction(CS, IFI, &AAR, InsertLifetime))
-    return false;
+  InlineResult IR = InlineFunction(CS, IFI, &AAR, InsertLifetime);
+  if (!IR)
+    return IR;
 
   if (InlinerFunctionImportStats != InlinerFunctionImportStatsOpts::No)
     ImportedFunctionsStats.recordInline(*Caller, *Callee);
@@ -286,7 +288,7 @@ static bool InlineCallIfPossible(
   if (!DisableInlinedAllocaMerging)
     mergeInlinedArrayAllocas(Caller, IFI, InlinedArrayAllocas, InlineHistory);
 
-  return true;
+  return IR; // success
 }
 
 /// Return true if inlining of CS can block the caller from being
@@ -365,6 +367,33 @@ shouldBeDeferred(Function *Caller, CallSite CS, InlineCost IC,
   return false;
 }
 
+static std::basic_ostream<char> &operator<<(std::basic_ostream<char> &R,
+                                            const ore::NV &Arg) {
+  return R << Arg.Val;
+}
+
+template <class RemarkT>
+RemarkT &operator<<(RemarkT &&R, const InlineCost &IC) {
+  using namespace ore;
+  if (IC.isAlways()) {
+    R << "(cost=always)";
+  } else if (IC.isNever()) {
+    R << "(cost=never)";
+  } else {
+    R << "(cost=" << ore::NV("Cost", IC.getCost())
+      << ", threshold=" << ore::NV("Threshold", IC.getThreshold()) << ")";
+  }
+  if (const char *Reason = IC.getReason())
+    R << ": " << ore::NV("Reason", Reason);
+  return R;
+}
+
+static std::string inlineCostStr(const InlineCost &IC) {
+  std::stringstream Remark;
+  Remark << IC;
+  return Remark.str();
+}
+
 /// Return the cost only if the inliner should attempt to inline at the given
 /// CallSite. If we return the cost, we will emit an optimisation remark later
 /// using that cost, so we won't do so from this function.
@@ -379,35 +408,32 @@ shouldInline(CallSite CS, function_ref<InlineCost(CallSite CS)> GetInlineCost,
   Function *Caller = CS.getCaller();
 
   if (IC.isAlways()) {
-    LLVM_DEBUG(dbgs() << "    Inlining: cost=always"
+    LLVM_DEBUG(dbgs() << "    Inlining " << inlineCostStr(IC)
                       << ", Call: " << *CS.getInstruction() << "\n");
     return IC;
   }
 
   if (IC.isNever()) {
-    LLVM_DEBUG(dbgs() << "    NOT Inlining: cost=never"
+    LLVM_DEBUG(dbgs() << "    NOT Inlining " << inlineCostStr(IC)
                       << ", Call: " << *CS.getInstruction() << "\n");
     ORE.emit([&]() {
       return OptimizationRemarkMissed(DEBUG_TYPE, "NeverInline", Call)
              << NV("Callee", Callee) << " not inlined into "
-             << NV("Caller", Caller)
-             << " because it should never be inlined (cost=never)";
+             << NV("Caller", Caller) << " because it should never be inlined "
+             << IC;
     });
-    return None;
+    return IC;
   }
 
   if (!IC) {
-    LLVM_DEBUG(dbgs() << "    NOT Inlining: cost=" << IC.getCost()
-                      << ", thres=" << IC.getThreshold()
+    LLVM_DEBUG(dbgs() << "    NOT Inlining " << inlineCostStr(IC)
                       << ", Call: " << *CS.getInstruction() << "\n");
     ORE.emit([&]() {
       return OptimizationRemarkMissed(DEBUG_TYPE, "TooCostly", Call)
              << NV("Callee", Callee) << " not inlined into "
-             << NV("Caller", Caller) << " because too costly to inline (cost="
-             << NV("Cost", IC.getCost())
-             << ", threshold=" << NV("Threshold", IC.getThreshold()) << ")";
+             << NV("Caller", Caller) << " because too costly to inline " << IC;
     });
-    return None;
+    return IC;
   }
 
   int TotalSecondaryCost = 0;
@@ -428,8 +454,7 @@ shouldInline(CallSite CS, function_ref<InlineCost(CallSite CS)> GetInlineCost,
     return None;
   }
 
-  LLVM_DEBUG(dbgs() << "    Inlining: cost=" << IC.getCost()
-                    << ", thres=" << IC.getThreshold()
+  LLVM_DEBUG(dbgs() << "    Inlining " << inlineCostStr(IC)
                     << ", Call: " << *CS.getInstruction() << '\n');
   return IC;
 }
@@ -461,6 +486,18 @@ bool LegacyInlinerBase::runOnSCC(CallGraphSCC &SCC) {
   return inlineCalls(SCC);
 }
 
+static void emit_inlined_into(OptimizationRemarkEmitter &ORE, DebugLoc &DLoc,
+                              const BasicBlock *Block, const Function &Callee,
+                              const Function &Caller, const InlineCost &IC) {
+  ORE.emit([&]() {
+    bool AlwaysInline = IC.isAlways();
+    StringRef RemarkName = AlwaysInline ? "AlwaysInline" : "Inlined";
+    return OptimizationRemark(DEBUG_TYPE, RemarkName, DLoc, Block)
+           << ore::NV("Callee", &Callee) << " inlined into "
+           << ore::NV("Caller", &Caller) << " with " << IC;
+  });
+}
+
 static bool
 inlineCallsImpl(CallGraphSCC &SCC, CallGraph &CG,
                 std::function<AssumptionCache &(Function &)> GetAssumptionCache,
@@ -585,8 +622,9 @@ inlineCallsImpl(CallGraphSCC &SCC, CallGraph &CG,
       Optional<InlineCost> OIC = shouldInline(CS, GetInlineCost, ORE);
       // If the policy determines that we should inline this function,
       // delete the call instead.
-      if (!OIC)
+      if (!OIC || !*OIC) {
         continue;
+      }
 
       // If this call site is dead and it is to a readonly function, we should
       // just delete the call instead of trying to inline it, regardless of
@@ -606,34 +644,21 @@ inlineCallsImpl(CallGraphSCC &SCC, CallGraph &CG,
         // Attempt to inline the function.
         using namespace ore;
 
-        if (!InlineCallIfPossible(CS, InlineInfo, InlinedArrayAllocas,
-                                  InlineHistoryID, InsertLifetime, AARGetter,
-                                  ImportedFunctionsStats)) {
+        InlineResult IR = InlineCallIfPossible(
+            CS, InlineInfo, InlinedArrayAllocas, InlineHistoryID,
+            InsertLifetime, AARGetter, ImportedFunctionsStats);
+        if (!IR) {
           ORE.emit([&]() {
             return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc,
                                             Block)
                    << NV("Callee", Callee) << " will not be inlined into "
-                   << NV("Caller", Caller);
+                   << NV("Caller", Caller) << ": " << NV("Reason", IR.message);
           });
           continue;
         }
         ++NumInlined;
 
-        ORE.emit([&]() {
-          bool AlwaysInline = OIC->isAlways();
-          StringRef RemarkName = AlwaysInline ? "AlwaysInline" : "Inlined";
-          OptimizationRemark R(DEBUG_TYPE, RemarkName, DLoc, Block);
-          R << NV("Callee", Callee) << " inlined into ";
-          R << NV("Caller", Caller);
-          if (AlwaysInline)
-            R << " with cost=always";
-          else {
-            R << " with cost=" << NV("Cost", OIC->getCost());
-            R << " (threshold=" << NV("Threshold", OIC->getThreshold());
-            R << ")";
-          }
-          return R;
-        });
+        emit_inlined_into(ORE, DLoc, Block, *Callee, *Caller, *OIC);
 
         // If inlining this function gave us any new call sites, throw them
         // onto our worklist to process.  They are useful inline candidates.
@@ -971,7 +996,7 @@ PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
 
       Optional<InlineCost> OIC = shouldInline(CS, GetInlineCost, ORE);
       // Check whether we want to inline this callsite.
-      if (!OIC)
+      if (!OIC || !*OIC)
         continue;
 
       // Setup the data structure used to plumb customization into the
@@ -987,32 +1012,19 @@ PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
 
       using namespace ore;
 
-      if (!InlineFunction(CS, IFI)) {
+      InlineResult IR = InlineFunction(CS, IFI);
+      if (!IR) {
         ORE.emit([&]() {
           return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc, Block)
                  << NV("Callee", &Callee) << " will not be inlined into "
-                 << NV("Caller", &F);
+                 << NV("Caller", &F) << ": " << NV("Reason", IR.message);
         });
         continue;
       }
       DidInline = true;
       InlinedCallees.insert(&Callee);
 
-      ORE.emit([&]() {
-        bool AlwaysInline = OIC->isAlways();
-        StringRef RemarkName = AlwaysInline ? "AlwaysInline" : "Inlined";
-        OptimizationRemark R(DEBUG_TYPE, RemarkName, DLoc, Block);
-        R << NV("Callee", &Callee) << " inlined into ";
-        R << NV("Caller", &F);
-        if (AlwaysInline)
-          R << " with cost=always";
-        else {
-          R << " with cost=" << NV("Cost", OIC->getCost());
-          R << " (threshold=" << NV("Threshold", OIC->getThreshold());
-          R << ")";
-        }
-        return R;
-      });
+      emit_inlined_into(ORE, DLoc, Block, Callee, F, *OIC);
 
       // Add any new callsites to defined functions to the worklist.
       if (!IFI.InlinedCallSites.empty()) {