1 files changed, 35 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index 060ca92e559a..28befd0aa1ce 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -26,6 +26,7 @@
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/LoopUtils.h"
 
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
@@ -175,6 +176,26 @@ SCEVExpander::findInsertPointAfter(Instruction *I,
   return IP;
 }
 
+void SCEVExpander::eraseDeadInstructions(Value *Root) {
+  SmallVector<Value *> WorkList;
+  SmallPtrSet<Value *, 8> DeletedValues;
+  append_range(WorkList, getAllInsertedInstructions());
+  while (!WorkList.empty()) {
+    Value *V = WorkList.pop_back_val();
+    if (DeletedValues.contains(V))
+      continue;
+    auto *I = dyn_cast<Instruction>(V);
+    if (!I || I == Root || !isInsertedInstruction(I) ||
+        !isInstructionTriviallyDead(I))
+      continue;
+    append_range(WorkList, I->operands());
+    InsertedValues.erase(I);
+    InsertedPostIncValues.erase(I);
+    DeletedValues.insert(I);
+    I->eraseFromParent();
+  }
+}
+
 BasicBlock::iterator
 SCEVExpander::GetOptimalInsertionPointForCastOf(Value *V) const {
   // Cast the argument at the beginning of the entry block, after
@@ -1239,10 +1260,13 @@ Value *SCEVExpander::tryToReuseLCSSAPhi(const SCEVAddRecExpr *S) {
     if (!isa<SCEVAddRecExpr>(ExitSCEV))
       continue;
     Type *PhiTy = PN.getType();
-    if (STy->isIntegerTy() && PhiTy->isPointerTy())
+    if (STy->isIntegerTy() && PhiTy->isPointerTy()) {
       ExitSCEV = SE.getPtrToIntExpr(ExitSCEV, STy);
-    else if (S->getType() != PN.getType())
+      if (isa<SCEVCouldNotCompute>(ExitSCEV))
+        continue;
+    } else if (S->getType() != PN.getType()) {
       continue;
+    }
 
     // Check if we can re-use the existing PN, by adjusting it with an expanded
     // offset, if the offset is simpler.
@@ -2184,8 +2208,15 @@ Value *SCEVExpander::generateOverflowCheck(const SCEVAddRecExpr *AR,
   // negative. If Step is known to be positive or negative, only create
   // either 1. or 2.
   auto ComputeEndCheck = [&]() -> Value * {
-    // Checking <u 0 is always false.
-    if (!Signed && Start->isZero() && SE.isKnownPositive(Step))
+    // Checking <u 0 is always false, if (Step * trunc ExitCount) does not wrap.
+    // TODO: Predicates that can be proven true/false should be discarded when
+    // the predicates are created, not late during expansion.
+    if (!Signed && Start->isZero() && SE.isKnownPositive(Step) &&
+        DstBits < SrcBits &&
+        ExitCount == SE.getZeroExtendExpr(SE.getTruncateExpr(ExitCount, ARTy),
+                                          ExitCount->getType()) &&
+        SE.willNotOverflow(Instruction::Mul, Signed, Step,
+                           SE.getTruncateExpr(ExitCount, ARTy)))
       return ConstantInt::getFalse(Loc->getContext());
 
     // Get the backedge taken count and truncate or extended to the AR type.