[llvm] r260706 - [LIR] Partially revert r252926(NFC), which introduced a very subtle change.

[Chad Rosier via llvm-commits]

Author: mcrosier
Date: Fri Feb 12 13:05:27 2016
New Revision: 260706

URL: http://llvm.org/viewvc/llvm-project?rev=260706&view=rev
Log:
[LIR] Partially revert r252926(NFC), which introduced a very subtle change.

In short, before r252926 we were comparing an unsigned (StoreSize) against an a
APInt (Stride), which is fine and well.  After we were zero extending the Stride
and then converting to an unsigned, which is not the same thing.  Obviously,
Stides can also be negative.  This commit just restores the original behavior.

AFAICT, it's not possible to write a test case to expose the issue because
the code already has checks to make sure the StoreSize can't overflow an
unsigned (which prevents the Stride from overflowing an unsigned as well).

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp?rev=260706&r1=260705&r2=260706&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp Fri Feb 12 13:05:27 2016
@@ -262,9 +262,9 @@ static unsigned getStoreSizeInBytes(Stor
   return (unsigned)SizeInBits >> 3;
 }
 
-static unsigned getStoreStride(const SCEVAddRecExpr *StoreEv) {
+static APInt getStoreStride(const SCEVAddRecExpr *StoreEv) {
   const SCEVConstant *ConstStride = cast<SCEVConstant>(StoreEv->getOperand(1));
-  return ConstStride->getAPInt().getZExtValue();
+  return ConstStride->getAPInt();
 }
 
 /// getMemSetPatternValue - If a strided store of the specified value is safe to
@@ -365,7 +365,7 @@ bool LoopIdiomRecognize::isLegalStore(St
   if (HasMemcpy) {
     // Check to see if the stride matches the size of the store.  If so, then we
     // know that every byte is touched in the loop.
-    unsigned Stride = getStoreStride(StoreEv);
+    APInt Stride = getStoreStride(StoreEv);
     unsigned StoreSize = getStoreSizeInBytes(SI, DL);
     if (StoreSize != Stride && StoreSize != -Stride)
       return false;
@@ -493,11 +493,11 @@ bool LoopIdiomRecognize::processLoopStor
     Value *FirstStorePtr = SL[i]->getPointerOperand();
     const SCEVAddRecExpr *FirstStoreEv =
         cast<SCEVAddRecExpr>(SE->getSCEV(FirstStorePtr));
-    unsigned FirstStride = getStoreStride(FirstStoreEv);
+    APInt FirstStride = getStoreStride(FirstStoreEv);
     unsigned FirstStoreSize = getStoreSizeInBytes(SL[i], DL);
 
     // See if we can optimize just this store in isolation.
-    if (FirstStride == FirstStoreSize || FirstStride == -FirstStoreSize) {
+    if (FirstStride == FirstStoreSize || -FirstStride == FirstStoreSize) {
       Heads.insert(SL[i]);
       continue;
     }
@@ -529,7 +529,7 @@ bool LoopIdiomRecognize::processLoopStor
       Value *SecondStorePtr = SL[k]->getPointerOperand();
       const SCEVAddRecExpr *SecondStoreEv =
           cast<SCEVAddRecExpr>(SE->getSCEV(SecondStorePtr));
-      unsigned SecondStride = getStoreStride(SecondStoreEv);
+      APInt SecondStride = getStoreStride(SecondStoreEv);
 
       if (FirstStride != SecondStride)
         continue;
@@ -595,7 +595,7 @@ bool LoopIdiomRecognize::processLoopStor
     Value *StoredVal = HeadStore->getValueOperand();
     Value *StorePtr = HeadStore->getPointerOperand();
     const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
-    unsigned Stride = getStoreStride(StoreEv);
+    APInt Stride = getStoreStride(StoreEv);
 
     // Check to see if the stride matches the size of the stores.  If so, then
     // we know that every byte is touched in the loop.
@@ -817,7 +817,7 @@ bool LoopIdiomRecognize::processLoopStor
 
   Value *StorePtr = SI->getPointerOperand();
   const SCEVAddRecExpr *StoreEv = cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
-  unsigned Stride = getStoreStride(StoreEv);
+  APInt Stride = getStoreStride(StoreEv);
   unsigned StoreSize = getStoreSizeInBytes(SI, DL);
   bool NegStride = StoreSize == -Stride;