Index: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
===================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
@@ -381,6 +381,14 @@
     return AArch64::X1;
   }
 
+  bool isCheapToSpeculateCttz() const override {
+    return true;
+  }
+
+  bool isCheapToSpeculateCtlz() const override {
+    return true;
+  }
+
 private:
   bool isExtFreeImpl(const Instruction *Ext) const override;
 
Index: llvm/trunk/test/Transforms/SimplifyCFG/AArch64/cttz-ctlz.ll
===================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/AArch64/cttz-ctlz.ll
+++ llvm/trunk/test/Transforms/SimplifyCFG/AArch64/cttz-ctlz.ll
@@ -0,0 +1,43 @@
+; RUN: opt -S -simplifycfg -mtriple=aarch64 < %s | FileCheck %s
+
+define i32 @ctlz(i32 %A) {
+; CHECK-LABEL: @ctlz(
+; CHECK: [[ICMP:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
+; CHECK-NEXT: [[CTZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
+; CHECK-NEXT: [[SEL:%[A-Za-z0-9.]+]] = select i1 [[ICMP]], i32 32, i32 [[CTZ]]
+; CHECK-NEXT: ret i32 [[SEL]]
+entry:
+  %tobool = icmp eq i32 %A, 0
+  br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true:
+  %0 = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
+  br label %cond.end
+
+cond.end:
+  %cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
+  ret i32 %cond
+}
+
+define i32 @cttz(i32 %A) {
+; CHECK-LABEL: @cttz(
+; CHECK: [[ICMP:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
+; CHECK-NEXT: [[CTZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
+; CHECK-NEXT: [[SEL:%[A-Za-z0-9.]+]] = select i1 [[ICMP]], i32 32, i32 [[CTZ]]
+; CHECK-NEXT: ret i32 [[SEL]]
+entry:
+  %tobool = icmp eq i32 %A, 0
+  br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true:
+  %0 = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
+  br label %cond.end
+
+cond.end:
+  %cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
+  ret i32 %cond
+}
+
+declare i32 @llvm.ctlz.i32(i32, i1)
+declare i32 @llvm.cttz.i32(i32, i1)
+