Index: llvm/lib/Transforms/IPO/FunctionAttrs.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -720,10 +720,16 @@
 
       // The accessors used on call site here do the right thing for calls and
       // invokes with operand bundles.
-      if (!CB.onlyReadsMemory() && !CB.onlyReadsMemory(UseIndex))
-        return Attribute::None;
-      if (!CB.doesNotAccessMemory(UseIndex))
+      if (CB.doesNotAccessMemory(UseIndex)) {
+        /* nop */
+      } else if (CB.onlyReadsMemory() || CB.onlyReadsMemory(UseIndex)) {
         IsRead = true;
+      } else if (CB.hasFnAttr(Attribute::WriteOnly) ||
+                 CB.dataOperandHasImpliedAttr(UseIndex, Attribute::WriteOnly)) {
+        IsWrite = true;
+      } else {
+        return Attribute::None;
+      }
       break;
     }
 
Index: llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
===================================================================
--- llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
+++ llvm/test/Analysis/TypeBasedAliasAnalysis/functionattrs.ll
@@ -49,7 +49,7 @@
   ret void
 }
 
-; CHECK: define void @test2_no(i8* nocapture %p, i8* nocapture readonly %q, i64 %n) #5 {
+; CHECK: define void @test2_no(i8* nocapture writeonly %p, i8* nocapture readonly %q, i64 %n) #5 {
 define void @test2_no(i8* %p, i8* %q, i64 %n) nounwind {
   call void @llvm.memcpy.p0i8.p0i8.i64(i8* %p, i8* %q, i64 %n, i1 false), !tbaa !2
   ret void
Index: llvm/test/Other/cgscc-devirt-iteration.ll
===================================================================
--- llvm/test/Other/cgscc-devirt-iteration.ll
+++ llvm/test/Other/cgscc-devirt-iteration.ll
@@ -112,7 +112,7 @@
 ; CHECK-NOT: read
 ; CHECK-SAME: noinline
 ; BEFORE-LABEL: define void @test3(i8* %src, i8* %dest, i64 %size)
-; AFTER-LABEL: define void @test3(i8* nocapture readonly %src, i8* nocapture %dest, i64 %size)
+; AFTER-LABEL: define void @test3(i8* nocapture readonly %src, i8* nocapture writeonly %dest, i64 %size)
   %fptr = alloca i8* (i8*, i8*, i64)*
   store i8* (i8*, i8*, i64)* @memcpy, i8* (i8*, i8*, i64)** %fptr
   %f = load i8* (i8*, i8*, i64)*, i8* (i8*, i8*, i64)** %fptr
Index: llvm/test/Transforms/FunctionAttrs/norecurse.ll
===================================================================
--- llvm/test/Transforms/FunctionAttrs/norecurse.ll
+++ llvm/test/Transforms/FunctionAttrs/norecurse.ll
@@ -50,7 +50,7 @@
 ; CHECK: Function Attrs
 ; CHECK-SAME: nounwind
 ; CHECK-NOT: norecurse
-; CHECK-NEXT: define void @intrinsic(i8* nocapture %dest, i8* nocapture readonly %src, i32 %len)
+; CHECK-NEXT: define void @intrinsic(i8* nocapture writeonly %dest, i8* nocapture readonly %src, i32 %len)
 define void @intrinsic(i8* %dest, i8* %src, i32 %len) {
   call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 %len, i1 false)
   ret void
Index: llvm/test/Transforms/FunctionAttrs/writeonly.ll
===================================================================
--- llvm/test/Transforms/FunctionAttrs/writeonly.ll
+++ llvm/test/Transforms/FunctionAttrs/writeonly.ll
@@ -78,15 +78,23 @@
 
 declare void @direct2_callee(i8* %p) writeonly
 
+; writeonly w/o nocapture is not enough
 ; CHECK: define void @direct2(i8* %p)
 define void @direct2(i8* %p) {
   call void @direct2_callee(i8* %p)
+  ; read back from global, read through pointer...
   ret void
 }
 
-declare void @direct3_callee(i8* writeonly %p)
+; CHECK: define void @direct2b(i8* nocapture writeonly %p)
+define void @direct2b(i8* %p) {
+  call void @direct2_callee(i8* nocapture %p)
+  ret void
+}
+
+declare void @direct3_callee(i8* nocapture writeonly %p)
 
-; CHECK: define void @direct3(i8* %p)
+; CHECK: define void @direct3(i8* nocapture writeonly %p)
 define void @direct3(i8* %p) {
   call void @direct3_callee(i8* %p)
   ret void
@@ -98,15 +106,15 @@
   ret void
 }
 
-; CHECK: define void @fptr_test2(i8* %p, void (i8*)* nocapture readonly %f)
+; CHECK: define void @fptr_test2(i8* nocapture writeonly %p, void (i8*)* nocapture readonly %f)
 define void @fptr_test2(i8* %p, void (i8*)* %f) {
-  call void %f(i8* writeonly %p)
+  call void %f(i8* nocapture writeonly %p)
   ret void
 }
 
-; CHECK: define void @fptr_test3(i8* %p, void (i8*)* nocapture readonly %f)
+; CHECK: define void @fptr_test3(i8* nocapture writeonly %p, void (i8*)* nocapture readonly %f)
 define void @fptr_test3(i8* %p, void (i8*)* %f) {
-  call void %f(i8* %p) writeonly
+  call void %f(i8* nocapture %p) writeonly
   ret void
 }