[CVP] Remove unnecessary checks for empty GNWR; NFC

The guaranteed no-wrap region is never empty, it always contains at
least zero, so these optimizations don't ever apply.

To make this more obviously true, replace the conversative return
in makeGNWR with an assertion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361698 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/IR/ConstantRange.cpp b/lib/IR/ConstantRange.cpp
index 549886271ff87d40e93b652b5c331696d95bd69a..0d44c3815b3b44b0f13551a98bb37730617e16b4 100644 (file)
--- a/lib/IR/ConstantRange.cpp
+++ b/lib/IR/ConstantRange.cpp
@@ -238,8 +238,7 @@ ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
 
   switch (BinOp) {
   default:
-    // Conservative answer: empty set
-    return getEmpty(BitWidth);
+    llvm_unreachable("Unsupported binary op");
 
   case Instruction::Add: {
     if (Unsigned)

diff --git a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 2c31e4aa6cd16120ce4cbda8bdf410367dc8aa3b..4e4715be61aed76db1e5d79c69f60b80f367877c 100644 (file)
--- a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -400,15 +400,12 @@ static bool processSwitch(SwitchInst *SI, LazyValueInfo *LVI,
 
 // See if we can prove that the given overflow intrinsic will not overflow.
 static bool willNotOverflow(WithOverflowInst *WO, LazyValueInfo *LVI) {
-  Value *RHS = WO->getRHS();
-  ConstantRange RRange = LVI->getConstantRange(RHS, WO->getParent(), WO);
+  ConstantRange LRange = LVI->getConstantRange(
+      WO->getLHS(), WO->getParent(), WO);
+  ConstantRange RRange = LVI->getConstantRange(
+      WO->getRHS(), WO->getParent(), WO);
   ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
       WO->getBinaryOp(), RRange, WO->getNoWrapKind());
-  // As an optimization, do not compute LRange if we do not need it.
-  if (NWRegion.isEmptySet())
-    return false;
-  Value *LHS = WO->getLHS();
-  ConstantRange LRange = LVI->getConstantRange(LHS, WO->getParent(), WO);
   return NWRegion.contains(LRange);
 }
 
@@ -626,36 +623,23 @@ static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
   Value *LHS = BinOp->getOperand(0);
   Value *RHS = BinOp->getOperand(1);
 
+  ConstantRange LRange = LVI->getConstantRange(LHS, BB, BinOp);
   ConstantRange RRange = LVI->getConstantRange(RHS, BB, BinOp);
 
-  // Initialize LRange only if we need it. If we know that guaranteed no wrap
-  // range for the given RHS range is empty don't spend time calculating the
-  // range for the LHS.
-  Optional<ConstantRange> LRange;
-  auto LazyLRange = [&] () {
-      if (!LRange)
-        LRange = LVI->getConstantRange(LHS, BB, BinOp);
-      return LRange.getValue();
-  };
-
   bool Changed = false;
   if (!NUW) {
     ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
         BinOp->getOpcode(), RRange, OBO::NoUnsignedWrap);
-    if (!NUWRange.isEmptySet()) {
-      bool NewNUW = NUWRange.contains(LazyLRange());
-      BinOp->setHasNoUnsignedWrap(NewNUW);
-      Changed |= NewNUW;
-    }
+    bool NewNUW = NUWRange.contains(LRange);
+    BinOp->setHasNoUnsignedWrap(NewNUW);
+    Changed |= NewNUW;
   }
   if (!NSW) {
     ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
         BinOp->getOpcode(), RRange, OBO::NoSignedWrap);
-    if (!NSWRange.isEmptySet()) {
-      bool NewNSW = NSWRange.contains(LazyLRange());
-      BinOp->setHasNoSignedWrap(NewNSW);
-      Changed |= NewNSW;
-    }
+    bool NewNSW = NSWRange.contains(LRange);
+    BinOp->setHasNoSignedWrap(NewNSW);
+    Changed |= NewNSW;
   }
 
   return Changed;