This case is solved by Scalar Replacement of Aggregates (DT) and

Early CSE pass so this patch reverts it to original source code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127574 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index e5ff00fc1dc09f938d572a17289ee6a4f73ac2d0..35c1d91d501663566a2feea3492df8f17c08bb6c 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -429,31 +429,9 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
     // the pointer we're loading and is producing the pointer we're storing,
     // then *this* store is dead (X = load P; store X -> P).
     if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
-      if (equivalentAddressValues(LI->getOperand(0), Ptr) &&
-          !SI.isVolatile()) {
-        if (LI == Val)
-          return EraseInstFromFunction(SI);
-        // load and store reference same memory location, the memory location
-        // is represented by getelementptr with two uses (load and store) and
-        // the getelementptr's base is alloca with single use. At this point,
-        // instructions from alloca to store can be removed.
-        // (this pattern is generated when bitfield is accessed.)
-        // For example,
-        // %u = alloca %struct.test, align 4               ; [#uses=1]
-        // %0 = getelementptr inbounds %struct.test* %u, i32 0, i32 0;[#uses=2]
-        // %1 = load i8* %0, align 4                       ; [#uses=1]
-        // %2 = and i8 %1, -16                             ; [#uses=1]
-        // %3 = or i8 %2, 5                                ; [#uses=1]
-        // store i8 %3, i8* %0, align 4
-        if (Ptr->hasNUses(2)) {
-          if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
-            if (isa<AllocaInst>(GEP->getOperand(0))) {
-              if (GEP->getOperand(0)->hasOneUse())
-                return EraseInstFromFunction(SI);
-            }
-          }
-        }
-      }
+      if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) &&
+          !SI.isVolatile())
+        return EraseInstFromFunction(SI);
       
       // Otherwise, this is a load from some other location.  Stores before it
       // may not be dead.