commit ca69b3bf6d91d633737682234f2ab0efe542ab22
author Francis Visoiu Mistrih <francisvm@yahoo.com> Tue Jun 05 00:27:24 2018 +0000
committer Francis Visoiu Mistrih <francisvm@yahoo.com> Tue Jun 05 00:27:24 2018 +0000
tree 59fa72befebc419fbc1a1f384621fa3516e98cfc
parent 34b6798ee21d046ceeb3689c9e42e82514986078

[ShrinkWrap] Add optimization remarks to the shrink-wrapping pass

Start by emitting remarks for very basic unsupported cases such as
irreducible CFGs and EHFunclets. The end goal is to be able to cover all
the cases where we give up with an explanation.

llvm-svn: 333972

llvm/lib/CodeGen/ShrinkWrap.cpp

diff --git a/llvm/lib/CodeGen/ShrinkWrap.cpp b/llvm/lib/CodeGen/ShrinkWrap.cpp
index 7647df0..d3454ca 100644
--- a/llvm/lib/CodeGen/ShrinkWrap.cpp
+++ b/llvm/lib/CodeGen/ShrinkWrap.cpp
@@ -63,6 +63,7 @@
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/MachinePostDominators.h"
 #include "llvm/CodeGen/RegisterClassInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
@@ -130,6 +131,9 @@
   /// are in the same loop.
   MachineLoopInfo *MLI;
 
+  // Emit remarks.
+  MachineOptimizationRemarkEmitter *ORE = nullptr;
+
   /// Frequency of the Entry block.
   uint64_t EntryFreq;
 
@@ -189,6 +193,7 @@
     Restore = nullptr;
     MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
     MLI = &getAnalysis<MachineLoopInfo>();
+    ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
     EntryFreq = MBFI->getEntryFreq();
     const TargetSubtargetInfo &Subtarget = MF.getSubtarget();
     const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
@@ -222,6 +227,7 @@
     AU.addRequired<MachineDominatorTree>();
     AU.addRequired<MachinePostDominatorTree>();
     AU.addRequired<MachineLoopInfo>();
+    AU.addRequired<MachineOptimizationRemarkEmitterPass>();
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 
@@ -248,6 +254,7 @@
 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(MachinePostDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass)
 INITIALIZE_PASS_END(ShrinkWrap, DEBUG_TYPE, "Shrink Wrap Pass", false, false)
 
 bool ShrinkWrap::useOrDefCSROrFI(const MachineInstr &MI,
@@ -432,6 +439,19 @@
   }
 }
 
+static bool giveUpWithRemarks(MachineOptimizationRemarkEmitter *ORE,
+                              StringRef RemarkName, StringRef RemarkMessage,
+                              const DiagnosticLocation &Loc,
+                              const MachineBasicBlock *MBB) {
+  ORE->emit([&]() {
+    return MachineOptimizationRemarkMissed(DEBUG_TYPE, RemarkName, Loc, MBB)
+           << RemarkMessage;
+  });
+
+  LLVM_DEBUG(dbgs() << RemarkMessage << '\n');
+  return false;
+}
+
 bool ShrinkWrap::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(MF.getFunction()) || MF.empty() || !isShrinkWrapEnabled(MF))
     return false;
@@ -448,8 +468,9 @@
     // results. Moreover, we may miss that the prologue and
     // epilogue are not in the same loop, leading to unbalanced
     // construction/deconstruction of the stack frame.
-    LLVM_DEBUG(dbgs() << "Irreducible CFGs are not supported yet\n");
-    return false;
+    return giveUpWithRemarks(ORE, "UnsupportedIrreducibleCFG",
+                             "Irreducible CFGs are not supported yet.",
+                             MF.getFunction().getSubprogram(), &MF.front());
   }
 
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
@@ -460,10 +481,10 @@
     LLVM_DEBUG(dbgs() << "Look into: " << MBB.getNumber() << ' '
                       << MBB.getName() << '\n');
 
-    if (MBB.isEHFuncletEntry()) {
-      LLVM_DEBUG(dbgs() << "EH Funclets are not supported yet.\n");
-      return false;
-    }
+    if (MBB.isEHFuncletEntry())
+      return giveUpWithRemarks(ORE, "UnsupportedEHFunclets",
+                               "EH Funclets are not supported yet.",
+                               MBB.front().getDebugLoc(), &MBB);
 
     if (MBB.isEHPad()) {
       // Push the prologue and epilogue outside of