From 55306bdea5d2d53be39f3ac59fadf5220ee6b5d0 Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Fri, 21 Dec 2012 00:07:35 +0000
Subject: Fix a bug in the code that checks if we can vectorize loops while
 using dynamic memory bound checks.  Before the fix we were able to vectorize
 this loop from the Livermore Loops benchmark:

for ( k=1 ; k<n ; k++ )
  x[k] = x[k-1] + y[k];



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170811 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Vectorize/LoopVectorize.cpp | 43 +++++++++++++++++-------------
 1 file changed, 24 insertions(+), 19 deletions(-)

(limited to 'lib/Transforms/Vectorize/LoopVectorize.cpp')

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 827c13ffc9..4a90d78c24 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1593,8 +1593,7 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
 
   ValueVector::iterator I, IE;
   for (I = Stores.begin(), IE = Stores.end(); I != IE; ++I) {
-    StoreInst *ST = dyn_cast<StoreInst>(*I);
-    assert(ST && "Bad StoreInst");
+    StoreInst *ST = cast<StoreInst>(*I);
     Value* Ptr = ST->getPointerOperand();
 
     if (isUniform(Ptr)) {
@@ -1609,8 +1608,7 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
   }
 
   for (I = Loads.begin(), IE = Loads.end(); I != IE; ++I) {
-    LoadInst *LD = dyn_cast<LoadInst>(*I);
-    assert(LD && "Bad LoadInst");
+    LoadInst *LD = cast<LoadInst>(*I);
     Value* Ptr = LD->getPointerOperand();
     // If we did *not* see this pointer before, insert it to the
     // read list. If we *did* see it before, then it is already in
@@ -1633,13 +1631,13 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
 
   // Find pointers with computable bounds. We are going to use this information
   // to place a runtime bound check.
-  bool RT = true;
+  bool CanDoRT = true;
   for (I = ReadWrites.begin(), IE = ReadWrites.end(); I != IE; ++I)
     if (hasComputableBounds(*I)) {
       PtrRtCheck.insert(SE, TheLoop, *I);
       DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n");
     } else {
-      RT = false;
+      CanDoRT = false;
       break;
     }
   for (I = Reads.begin(), IE = Reads.end(); I != IE; ++I)
@@ -1647,23 +1645,23 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
       PtrRtCheck.insert(SE, TheLoop, *I);
       DEBUG(dbgs() << "LV: Found a runtime check ptr:" << **I <<"\n");
     } else {
-      RT = false;
+      CanDoRT = false;
       break;
     }
 
   // Check that we did not collect too many pointers or found a
   // unsizeable pointer.
-  if (!RT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) {
+  if (!CanDoRT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) {
     PtrRtCheck.reset();
-    RT = false;
+    CanDoRT = false;
   }
 
-  PtrRtCheck.Need = RT;
-
-  if (RT) {
+  if (CanDoRT) {
     DEBUG(dbgs() << "LV: We can perform a memory runtime check if needed.\n");
   }
 
+  bool NeedRTCheck = false;
+
   // Now that the pointers are in two lists (Reads and ReadWrites), we
   // can check that there are no conflicts between each of the writes and
   // between the writes to the reads.
@@ -1678,12 +1676,12 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
          it != e; ++it) {
       if (!isIdentifiedObject(*it)) {
         DEBUG(dbgs() << "LV: Found an unidentified write ptr:"<< **it <<"\n");
-        return RT;
+        NeedRTCheck = true;
       }
       if (!WriteObjects.insert(*it)) {
         DEBUG(dbgs() << "LV: Found a possible write-write reorder:"
               << **it <<"\n");
-        return RT;
+        return false;
       }
     }
     TempObjects.clear();
@@ -1696,20 +1694,27 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
          it != e; ++it) {
       if (!isIdentifiedObject(*it)) {
         DEBUG(dbgs() << "LV: Found an unidentified read ptr:"<< **it <<"\n");
-        return RT;
+        NeedRTCheck = true;
       }
       if (WriteObjects.count(*it)) {
         DEBUG(dbgs() << "LV: Found a possible read/write reorder:"
               << **it <<"\n");
-        return RT;
+        return false;
       }
     }
     TempObjects.clear();
   }
 
-  // It is safe to vectorize and we don't need any runtime checks.
-  DEBUG(dbgs() << "LV: We don't need a runtime memory check.\n");
-  PtrRtCheck.reset();
+  PtrRtCheck.Need = NeedRTCheck;
+  if (NeedRTCheck && !CanDoRT) {
+    DEBUG(dbgs() << "LV: We can't vectorize because we can't find " <<
+          "the array bounds.\n");
+    PtrRtCheck.reset();
+    return false;
+  }
+
+  DEBUG(dbgs() << "LV: We "<< (NeedRTCheck ? "" : "don't") <<
+        " need a runtime memory check.\n");
   return true;
 }
 
-- 
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