[llvm] 4919365 - [ValueTracking] reduce code duplication; NFC

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2021-04-14T08:32:42-04:00
New Revision: 49193653974ae96b756b8ff13668d07d6252aa77

URL: https://github.com/llvm/llvm-project/commit/49193653974ae96b756b8ff13668d07d6252aa77
DIFF: https://github.com/llvm/llvm-project/commit/49193653974ae96b756b8ff13668d07d6252aa77.diff

LOG: [ValueTracking] reduce code duplication; NFC

The start value can't be null for something to be a non-zero
recurrence, so hoist that common check out of the switch.

Subsequent checks may be incomplete or over-specified as noted in:
D100408

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d61f5ac47c70..2d933489447d 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2213,33 +2213,31 @@ static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value)
   return true;
 }
 
+/// Try to detect a recurrence that monotonically increases from a non-zero
+/// starting value. These are common as induction variables.
 static bool isNonZeroRecurrence(const PHINode *PN) {
-  // Try and detect a recurrence that monotonically increases from a
-  // starting value, as these are common as induction variables.
   BinaryOperator *BO = nullptr;
   Value *Start = nullptr, *Step = nullptr;
   const APInt *StartC, *StepC;
   if (!matchSimpleRecurrence(PN, BO, Start, Step) ||
-      !match(Start, m_APInt(StartC)))
+      !match(Start, m_APInt(StartC)) || StartC->isNullValue())
     return false;
 
   switch (BO->getOpcode()) {
   case Instruction::Add:
     return match(Step, m_APInt(StepC)) &&
-           ((BO->hasNoUnsignedWrap() && !StartC->isNullValue() &&
-             !StepC->isNullValue()) ||
+           ((BO->hasNoUnsignedWrap() && !StepC->isNullValue()) ||
             (BO->hasNoSignedWrap() && StartC->isStrictlyPositive() &&
              StepC->isNonNegative()));
   case Instruction::Mul:
-    return !StartC->isNullValue() && match(Step, m_APInt(StepC)) &&
+    return match(Step, m_APInt(StepC)) &&
            ((BO->hasNoUnsignedWrap() && !StepC->isNullValue()) ||
             (BO->hasNoSignedWrap() && StepC->isStrictlyPositive()));
   case Instruction::Shl:
-    return !StartC->isNullValue() &&
-           (BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap());
+    return BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap();
   case Instruction::AShr:
   case Instruction::LShr:
-    return !StartC->isNullValue() && BO->isExact();
+    return BO->isExact();
   default:
     return false;
   }