Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.)

[oota-llvm.git] / lib / Transforms / Scalar / CorrelatedValuePropagation.cpp

diff --git a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 3fd72a4306cb405bfdad676e8026fea307778e18..075c0351534dc1d196c0a59dc61075a661d8bd7a 100644 (file)
--- a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -11,19 +11,22 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define DEBUG_TYPE "correlated-value-propagation"
 #include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/LazyValueInfo.h"
-#include "llvm/Support/CFG.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/Statistic.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "correlated-value-propagation"
+
 STATISTIC(NumPhis,      "Number of phis propagated");
 STATISTIC(NumSelects,   "Number of selects propagated");
 STATISTIC(NumMemAccess, "Number of memory access targets propagated");
@@ -46,9 +49,9 @@ namespace {
      initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
     }
 
-    bool runOnFunction(Function &F);
+    bool runOnFunction(Function &F) override;
 
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.addRequired<LazyValueInfo>();
     }
   };
@@ -97,15 +100,33 @@ bool CorrelatedValuePropagation::processPHI(PHINode *P) {
     Value *Incoming = P->getIncomingValue(i);
     if (isa<Constant>(Incoming)) continue;
 
-    Constant *C = LVI->getConstantOnEdge(P->getIncomingValue(i),
-                                         P->getIncomingBlock(i),
-                                         BB);
-    if (!C) continue;
+    Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB);
+
+    // Look if the incoming value is a select with a constant but LVI tells us
+    // that the incoming value can never be that constant. In that case replace
+    // the incoming value with the other value of the select. This often allows
+    // us to remove the select later.
+    if (!V) {
+      SelectInst *SI = dyn_cast<SelectInst>(Incoming);
+      if (!SI) continue;
+
+      Constant *C = dyn_cast<Constant>(SI->getFalseValue());
+      if (!C) continue;
 
-    P->setIncomingValue(i, C);
+      if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
+                                  P->getIncomingBlock(i), BB) !=
+          LazyValueInfo::False)
+        continue;
+
+      DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
+      V = SI->getTrueValue();
+    }
+
+    P->setIncomingValue(i, V);
     Changed = true;
   }
 
+  // FIXME: Provide DL, TLI, DT, AT to SimplifyInstruction.
   if (Value *V = SimplifyInstruction(P)) {
     P->replaceAllUsesWith(V);
     P->eraseFromParent();
@@ -119,7 +140,7 @@ bool CorrelatedValuePropagation::processPHI(PHINode *P) {
 }
 
 bool CorrelatedValuePropagation::processMemAccess(Instruction *I) {
-  Value *Pointer = 0;
+  Value *Pointer = nullptr;
   if (LoadInst *L = dyn_cast<LoadInst>(I))
     Pointer = L->getPointerOperand();
   else
@@ -199,7 +220,7 @@ bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
   // Analyse each switch case in turn.  This is done in reverse order so that
   // removing a case doesn't cause trouble for the iteration.
   bool Changed = false;
-  for (SwitchInst::CaseIt CI = SI->caseEnd(), CE = SI->caseBegin(); CI-- != CE;
+  for (SwitchInst::CaseIt CI = SI->case_end(), CE = SI->case_begin(); CI-- != CE;
        ) {
     ConstantInt *Case = CI.getCaseValue();
 
@@ -235,6 +256,11 @@ bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
       // This case never fires - remove it.
       CI.getCaseSuccessor()->removePredecessor(BB);
       SI->removeCase(CI); // Does not invalidate the iterator.
+
+      // The condition can be modified by removePredecessor's PHI simplification
+      // logic.
+      Cond = SI->getCondition();
+
       ++NumDeadCases;
       Changed = true;
     } else if (State == LazyValueInfo::True) {
@@ -257,6 +283,9 @@ bool CorrelatedValuePropagation::processSwitch(SwitchInst *SI) {
 }
 
 bool CorrelatedValuePropagation::runOnFunction(Function &F) {
+  if (skipOptnoneFunction(F))
+    return false;
+
   LVI = &getAnalysis<LazyValueInfo>();
 
   bool FnChanged = false;