X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoads.cpp;h=4b2fa3c6505a14a1e0b4a5a1eacc9abe5aa7cab6;hb=92989cbe8452a9406f6e0d3c5709b5745f27158a;hp=624c5a18d6793c2cabbaf0c5e8fc8b8c520a47dd;hpb=f2e7bb5d2f983472df351572ffea52f7b0b93b25;p=oota-llvm.git

diff --git a/lib/Analysis/Loads.cpp b/lib/Analysis/Loads.cpp
index 624c5a18d67..4b2fa3c6505 100644
--- a/lib/Analysis/Loads.cpp
+++ b/lib/Analysis/Loads.cpp
@@ -118,7 +118,8 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
   // from/to.  If so, the previous load or store would have already trapped,
   // so there is no harm doing an extra load (also, CSE will later eliminate
   // the load entirely).
-  BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
+  BasicBlock::iterator BBI = ScanFrom->getIterator(),
+                       E = ScanFrom->getParent()->begin();
 
   // We can at least always strip pointer casts even though we can't use the
   // base here.
@@ -161,6 +162,18 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
   return false;
 }
 
+/// DefMaxInstsToScan - the default number of maximum instructions
+/// to scan in the block, used by FindAvailableLoadedValue().
+/// FindAvailableLoadedValue() was introduced in r60148, to improve jump
+/// threading in part by eliminating partially redundant loads.
+/// At that point, the value of MaxInstsToScan was already set to '6'
+/// without documented explanation.
+cl::opt<unsigned>
+llvm::DefMaxInstsToScan("available-load-scan-limit", cl::init(6), cl::Hidden,
+  cl::desc("Use this to specify the default maximum number of instructions "
+           "to scan backward from a given instruction, when searching for "
+           "available loaded value"));
+
 /// \brief Scan the ScanBB block backwards to see if we have the value at the
 /// memory address *Ptr locally available within a small number of instructions.
 ///
@@ -199,7 +212,7 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
   while (ScanFrom != ScanBB->begin()) {
     // We must ignore debug info directives when counting (otherwise they
     // would affect codegen).
-    Instruction *Inst = --ScanFrom;
+    Instruction *Inst = &*--ScanFrom;
     if (isa<DbgInfoIntrinsic>(Inst))
       continue;
 
@@ -246,9 +259,7 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
 
       // If we have alias analysis and it says the store won't modify the loaded
       // value, ignore the store.
-      if (AA &&
-          (AA->getModRefInfo(SI, StrippedPtr, AccessSize) &
-           AliasAnalysis::Mod) == 0)
+      if (AA && (AA->getModRefInfo(SI, StrippedPtr, AccessSize) & MRI_Mod) == 0)
         continue;
 
       // Otherwise the store that may or may not alias the pointer, bail out.
@@ -261,8 +272,7 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
       // If alias analysis claims that it really won't modify the load,
       // ignore it.
       if (AA &&
-          (AA->getModRefInfo(Inst, StrippedPtr, AccessSize) &
-           AliasAnalysis::Mod) == 0)
+          (AA->getModRefInfo(Inst, StrippedPtr, AccessSize) & MRI_Mod) == 0)
         continue;
 
       // May modify the pointer, bail out.