Index: lib/Transforms/Scalar/GVN.cpp
===================================================================
--- lib/Transforms/Scalar/GVN.cpp
+++ lib/Transforms/Scalar/GVN.cpp
@@ -1463,6 +1463,13 @@
                                              UndefValue::get(LI->getType())));
       continue;
     }
+    
+    // Loading from calloc (which zero initializes memory) -> zero
+    if (isCallocLikeFn(DepInst, TLI)) {
+      ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
+                                             Constant::getNullValue(LI->getType())));
+      continue;
+    }
 
     if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
       // Reject loads and stores that are to the same address but are of
@@ -1988,6 +1995,15 @@
     }
   }
 
+  // If this load follows a calloc (which zero initializes memory),
+  // then the loaded value is zero
+  if (isCallocLikeFn(DepInst, TLI)) {
+    L->replaceAllUsesWith(Constant::getNullValue(L->getType()));
+    markInstructionForDeletion(L);
+    ++NumGVNLoad;
+    return true;
+  }
+
   return false;
 }
 
Index: test/Transforms/GVN/calloc-load-removal.ll
===================================================================
--- /dev/null
+++ test/Transforms/GVN/calloc-load-removal.ll
@@ -0,0 +1,25 @@
+; RUN: opt -S -basicaa -gvn < %s | FileCheck %s
+; RUN: opt -S -basicaa -gvn -disable-simplify-libcalls < %s | FileCheck %s -check-prefix=CHECK_NO_LIBCALLS
+; check that loads from calloc are recognized as being zero
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+; Function Attrs: nounwind uwtable
+define i32 @test1() {
+  %1 = tail call noalias i8* @calloc(i64 1, i64 4) #2
+  %2 = bitcast i8* %1 to i32*
+  ; This load is trivially constant zero
+  %3 = load i32* %2, align 4
+  ret i32 %3
+
+; CHECK-LABEL: @test1(
+; CHECK-NOT: %3 = load i32* %2, align 4 
+; CHECK: ret i32 0
+
+; CHECK_NO_LIBCALLS-LABEL: @test1(
+; CHECK_NO_LIBCALLS: load
+; CHECK_NO_LIBCALLS: ret i32 %
+
+}
+
+declare noalias i8* @calloc(i64, i64)