diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index f55aff31255..37c946223ed 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4629,60 +4629,11 @@ Instruction *InstCombiner::FoldGEPICmp(User *GEPLHS, Value *RHS,
 
   Value *PtrBase = GEPLHS->getOperand(0);
   if (PtrBase == RHS) {
-    // As an optimization, we don't actually have to compute the actual value of
-    // OFFSET if this is a icmp_eq or icmp_ne comparison, just return whether 
-    // each index is zero or not.
-    if (Cond == ICmpInst::ICMP_EQ || Cond == ICmpInst::ICMP_NE) {
-      Instruction *InVal = 0;
-      gep_type_iterator GTI = gep_type_begin(GEPLHS);
-      for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i, ++GTI) {
-        bool EmitIt = true;
-        if (Constant *C = dyn_cast<Constant>(GEPLHS->getOperand(i))) {
-          if (isa<UndefValue>(C))  // undef index -> undef.
-            return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
-          if (C->isNullValue())
-            EmitIt = false;
-          else if (TD->getABITypeSize(GTI.getIndexedType()) == 0) {
-            EmitIt = false;  // This is indexing into a zero sized array?
-          } else if (isa<ConstantInt>(C))
-            return ReplaceInstUsesWith(I, // No comparison is needed here.
-                                 ConstantInt::get(Type::Int1Ty, 
-                                                  Cond == ICmpInst::ICMP_NE));
-        }
-
-        if (EmitIt) {
-          Instruction *Comp =
-            new ICmpInst(Cond, GEPLHS->getOperand(i),
-                    Constant::getNullValue(GEPLHS->getOperand(i)->getType()));
-          if (InVal == 0)
-            InVal = Comp;
-          else {
-            InVal = InsertNewInstBefore(InVal, I);
-            InsertNewInstBefore(Comp, I);
-            if (Cond == ICmpInst::ICMP_NE)   // True if any are unequal
-              InVal = BinaryOperator::createOr(InVal, Comp);
-            else                              // True if all are equal
-              InVal = BinaryOperator::createAnd(InVal, Comp);
-          }
-        }
-      }
-
-      if (InVal)
-        return InVal;
-      else
-        // No comparison is needed here, all indexes = 0
-        ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty, 
-                                                Cond == ICmpInst::ICMP_EQ));
-    }
-
-    // Only lower this if the icmp is the only user of the GEP or if we expect
-    // the result to fold to a constant!
-    if (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) {
-      // ((gep Ptr, OFFSET) cmp Ptr)   ---> (OFFSET cmp 0).
-      Value *Offset = EmitGEPOffset(GEPLHS, I, *this);
-      return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
-                          Constant::getNullValue(Offset->getType()));
-    }
+    // ((gep Ptr, OFFSET) cmp Ptr)   ---> (OFFSET cmp 0).
+    // This transformation is valid because we know pointers can't overflow.
+    Value *Offset = EmitGEPOffset(GEPLHS, I, *this);
+    return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
+                        Constant::getNullValue(Offset->getType()));
   } else if (User *GEPRHS = dyn_castGetElementPtr(RHS)) {
     // If the base pointers are different, but the indices are the same, just
     // compare the base pointer.
diff --git a/test/Transforms/InstCombine/2008-02-04-GEPIdxBug.ll b/test/Transforms/InstCombine/2008-02-04-GEPIdxBug.ll
new file mode 100644
index 00000000000..6814e2febce
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-02-04-GEPIdxBug.ll
@@ -0,0 +1,33 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {icmp eq i32 %indvar, 0}
+; PR1978
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i686-apple-darwin8"
+	%struct.x = type <{ i8 }>
+@.str = internal constant [6 x i8] c"Main!\00"		; <[6 x i8]*> [#uses=1]
+@.str1 = internal constant [12 x i8] c"destroy %p\0A\00"		; <[12 x i8]*> [#uses=1]
+
+define i32 @main() nounwind  {
+entry:
+	%orientations = alloca [1 x [1 x %struct.x]]		; <[1 x [1 x %struct.x]]*> [#uses=2]
+	%tmp3 = call i32 @puts( i8* getelementptr ([6 x i8]* @.str, i32 0, i32 0) ) nounwind 		; <i32> [#uses=0]
+	%tmp45 = getelementptr [1 x [1 x %struct.x]]* %orientations, i32 1, i32 0, i32 0		; <%struct.x*> [#uses=1]
+	%orientations62 = getelementptr [1 x [1 x %struct.x]]* %orientations, i32 0, i32 0, i32 0		; <%struct.x*> [#uses=1]
+	br label %bb10
+
+bb10:		; preds = %bb10, %entry
+	%indvar = phi i32 [ 0, %entry ], [ %indvar.next, %bb10 ]		; <i32> [#uses=2]
+	%tmp.0.reg2mem.0.rec = mul i32 %indvar, -1		; <i32> [#uses=1]
+	%tmp12.rec = add i32 %tmp.0.reg2mem.0.rec, -1		; <i32> [#uses=1]
+	%tmp12 = getelementptr %struct.x* %tmp45, i32 %tmp12.rec		; <%struct.x*> [#uses=2]
+	%tmp16 = call i32 (i8*, ...)* @printf( i8* getelementptr ([12 x i8]* @.str1, i32 0, i32 0), %struct.x* %tmp12 ) nounwind 		; <i32> [#uses=0]
+	%tmp84 = icmp eq %struct.x* %tmp12, %orientations62		; <i1> [#uses=1]
+	%indvar.next = add i32 %indvar, 1		; <i32> [#uses=1]
+	br i1 %tmp84, label %bb17, label %bb10
+
+bb17:		; preds = %bb10
+	ret i32 0
+}
+
+declare i32 @puts(i8*)
+
+declare i32 @printf(i8*, ...)