Revert "InstCombine rule to fold truncs whose value is available"

This reverts commit r274853.
Caused failure in ppcBE build

llvm-svn: 274943

1 files changed, 1 insertions, 23 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 395e83661d5..20556157188 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -13,10 +13,9 @@
 
 #include "InstCombineInternal.h"
 #include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/Loads.h"
-#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/PatternMatch.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 using namespace llvm;
 using namespace PatternMatch;
 
@@ -576,27 +575,6 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
   if (Instruction *I = foldVecTruncToExtElt(CI, *this, DL))
     return I;
 
-  // When trunc operand is a widened load, see if we can get the value from a
-  // previous store/load
-  if (auto *LI = dyn_cast<LoadInst>(Src)) {
-    BasicBlock::iterator BBI(*LI);
-
-    // Scan a few instructions up from LI and if we find a partial load/store
-    // of Type DestTy that feeds into LI, we can replace all uses of the trunc
-    // with the load/store value.
-    // This replacement can be done only in the case of non-volatile loads, with
-    // ordering at most unordered. If the load is atomic, its only use should be
-    // the trunc instruction. We don't want to allow other users of LI to see a
-    // value that is out of sync with the value we're folding the trunc to (in
-    // case of a race).
-    if (LI->isUnordered() && (!LI->isAtomic() || LI->hasOneUse()))
-      if (Value *AvailableVal = FindAvailableLoadedValue(
-              LI->getPointerOperand(), DestTy, LI->isAtomic(), LI->getParent(),
-              BBI, DefMaxInstsToScan))
-        return replaceInstUsesWith(
-            CI, Builder->CreateBitOrPointerCast(AvailableVal, CI.getType(),
-                                                CI.getName() + ".cast"));
-  }
   return nullptr;
 }