Index: llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ llvm/trunk/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -740,6 +740,11 @@
     if (isa<PHINode>(U))
       return TTI::TCC_Free; // Model all PHI nodes as free.
 
+    // Static alloca doesn't generate target instructions.
+    if (auto *A = dyn_cast<AllocaInst>(U))
+      if (A->isStaticAlloca())
+        return TTI::TCC_Free;
+
     if (const GEPOperator *GEP = dyn_cast<GEPOperator>(U)) {
       return static_cast<T *>(this)->getGEPCost(GEP->getSourceElementType(),
                                                 GEP->getPointerOperand(),
Index: llvm/trunk/test/Analysis/CostModel/X86/costmodel.ll
===================================================================
--- llvm/trunk/test/Analysis/CostModel/X86/costmodel.ll
+++ llvm/trunk/test/Analysis/CostModel/X86/costmodel.ll
@@ -7,6 +7,14 @@
 
 define i64 @foo(i64 %arg) {
 
+  ; LATENCY:  cost of 0 {{.*}} alloca i32
+  ; CODESIZE: cost of 0 {{.*}} alloca i32
+  %A1 = alloca i32, align 8
+
+  ; LATENCY:  cost of 1 {{.*}} alloca i64, i64 undef
+  ; CODESIZE: cost of 1 {{.*}} alloca i64, i64 undef
+  %A2 = alloca i64, i64 undef, align 8
+
   ; LATENCY:  cost of 1 {{.*}} %I64 = add
   ; CODESIZE: cost of 1 {{.*}} %I64 = add
   %I64 = add i64 undef, undef