Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1312,6 +1312,12 @@
     This indicates that callee does not free the pointer argument. This is not
     a valid attribute for return values.
 
+``noreadafterunwind``
+    This indicates that the caller will not read the underlying object of a
+    pointer argument if the call unwinds. As such, stores to the object that
+    are only visible on unwind paths can be elided. This attribute cannot be
+    applied to return values.
+
 .. _nest:
 
 ``nest``
Index: llvm/include/llvm/Bitcode/LLVMBitCodes.h
===================================================================
--- llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -713,6 +713,7 @@
   ATTR_KIND_SKIP_PROFILE = 85,
   ATTR_KIND_MEMORY = 86,
   ATTR_KIND_NOFPCLASS = 87,
+  ATTR_KIND_NOREADAFTERUNWIND = 88,
 };
 
 enum ComdatSelectionKindCodes {
Index: llvm/include/llvm/IR/Attributes.td
===================================================================
--- llvm/include/llvm/IR/Attributes.td
+++ llvm/include/llvm/IR/Attributes.td
@@ -151,6 +151,9 @@
 /// Function does not deallocate memory.
 def NoFree : EnumAttr<"nofree", [FnAttr, ParamAttr]>;
 
+/// Argument is not read if the call unwinds.
+def NoReadAfterUnwind : EnumAttr<"noreadafterunwind", [ParamAttr]>;
+
 /// Disable implicit floating point insts.
 def NoImplicitFloat : EnumAttr<"noimplicitfloat", [FnAttr]>;
 
Index: llvm/lib/Analysis/AliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/AliasAnalysis.cpp
+++ llvm/lib/Analysis/AliasAnalysis.cpp
@@ -896,7 +896,7 @@
 
   // Byval goes out of scope on unwind.
   if (auto *A = dyn_cast<Argument>(Object))
-    return A->hasByValAttr();
+    return A->hasByValAttr() || A->hasAttribute(Attribute::NoReadAfterUnwind);
 
   // A noalias return is not accessible from any other code. If the pointer
   // does not escape prior to the unwind, then the caller cannot access the
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -2060,6 +2060,8 @@
     return Attribute::Hot;
   case bitc::ATTR_KIND_PRESPLIT_COROUTINE:
     return Attribute::PresplitCoroutine;
+  case bitc::ATTR_KIND_NOREADAFTERUNWIND:
+    return Attribute::NoReadAfterUnwind;
   }
 }
 
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -809,6 +809,8 @@
     return bitc::ATTR_KIND_MUSTPROGRESS;
   case Attribute::PresplitCoroutine:
     return bitc::ATTR_KIND_PRESPLIT_COROUTINE;
+  case Attribute::NoReadAfterUnwind:
+    return bitc::ATTR_KIND_NOREADAFTERUNWIND;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None:
Index: llvm/lib/IR/Attributes.cpp
===================================================================
--- llvm/lib/IR/Attributes.cpp
+++ llvm/lib/IR/Attributes.cpp
@@ -1961,7 +1961,8 @@
           .addAttribute(Attribute::ReadNone)
           .addAttribute(Attribute::ReadOnly)
           .addAttribute(Attribute::Dereferenceable)
-          .addAttribute(Attribute::DereferenceableOrNull);
+          .addAttribute(Attribute::DereferenceableOrNull)
+          .addAttribute(Attribute::NoReadAfterUnwind);
     if (ASK & ASK_UNSAFE_TO_DROP)
       Incompatible.addAttribute(Attribute::Nest)
           .addAttribute(Attribute::SwiftError)
Index: llvm/lib/Transforms/Utils/CodeExtractor.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -990,6 +990,7 @@
       case Attribute::ImmArg:
       case Attribute::ByRef:
       case Attribute::WriteOnly:
+      case Attribute::NoReadAfterUnwind:
       //  These are not really attributes.
       case Attribute::None:
       case Attribute::EndAttrKinds:
Index: llvm/test/Bitcode/attributes.ll
===================================================================
--- llvm/test/Bitcode/attributes.ll
+++ llvm/test/Bitcode/attributes.ll
@@ -511,6 +511,11 @@
 ; CHECK: define void @f88() [[SKIPPROFILE:#[0-9]+]]
 define void @f88() skipprofile { ret void }
 
+; CHECK: define void @f89(ptr noreadafterunwind %p)
+define void @f89(ptr noreadafterunwind %p) {
+  ret void
+}
+
 ; CHECK: attributes #0 = { noreturn }
 ; CHECK: attributes #1 = { nounwind }
 ; CHECK: attributes #2 = { memory(none) }
Index: llvm/test/Transforms/DeadStoreElimination/simple.ll
===================================================================
--- llvm/test/Transforms/DeadStoreElimination/simple.ll
+++ llvm/test/Transforms/DeadStoreElimination/simple.ll
@@ -515,12 +515,10 @@
   ret void
 }
 ; Same as previous case, but with an sret argument.
-; TODO: The first store could be eliminated if sret is not visible on unwind.
-define void @test34_sret(ptr noalias sret(i32) %p) {
-; CHECK-LABEL: @test34_sret(
-; CHECK-NEXT:    store i32 1, ptr [[P:%.*]], align 4
+define void @test34_noreadafterunwind(ptr noalias noreadafterunwind %p) {
+; CHECK-LABEL: @test34_noreadafterunwind(
 ; CHECK-NEXT:    call void @unknown_func()
-; CHECK-NEXT:    store i32 0, ptr [[P]], align 4
+; CHECK-NEXT:    store i32 0, ptr [[P:%.*]], align 4
 ; CHECK-NEXT:    ret void
 ;
   store i32 1, ptr %p
Index: llvm/test/Transforms/LICM/scalar-promote-unwind.ll
===================================================================
--- llvm/test/Transforms/LICM/scalar-promote-unwind.ll
+++ llvm/test/Transforms/LICM/scalar-promote-unwind.ll
@@ -147,9 +147,8 @@
   ret void
 }
 
-; TODO: sret could be specified to not be accessed on unwind either.
-define void @test_sret(ptr noalias sret(i32) %a, i1 zeroext %y) uwtable {
-; CHECK-LABEL: @test_sret(
+define void @test_noreadafterunwind(ptr noalias noreadafterunwind %a, i1 zeroext %y) uwtable {
+; CHECK-LABEL: @test_noreadafterunwind(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[A_PROMOTED:%.*]] = load i32, ptr [[A:%.*]], align 4
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
@@ -157,7 +156,6 @@
 ; CHECK-NEXT:    [[ADD1:%.*]] = phi i32 [ [[A_PROMOTED]], [[ENTRY:%.*]] ], [ [[ADD:%.*]], [[FOR_INC:%.*]] ]
 ; CHECK-NEXT:    [[I_03:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[INC:%.*]], [[FOR_INC]] ]
 ; CHECK-NEXT:    [[ADD]] = add nsw i32 [[ADD1]], 1
-; CHECK-NEXT:    store i32 [[ADD]], ptr [[A]], align 4
 ; CHECK-NEXT:    br i1 [[Y:%.*]], label [[IF_THEN:%.*]], label [[FOR_INC]]
 ; CHECK:       if.then:
 ; CHECK-NEXT:    tail call void @f()
@@ -167,6 +165,8 @@
 ; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 10000
 ; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_COND_CLEANUP:%.*]], label [[FOR_BODY]]
 ; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[ADD_LCSSA:%.*]] = phi i32 [ [[ADD]], [[FOR_INC]] ]
+; CHECK-NEXT:    store i32 [[ADD_LCSSA]], ptr [[A]], align 4
 ; CHECK-NEXT:    ret void
 ;
 entry:
Index: llvm/test/Transforms/MemCpyOpt/callslot_throw.ll
===================================================================
--- llvm/test/Transforms/MemCpyOpt/callslot_throw.ll
+++ llvm/test/Transforms/MemCpyOpt/callslot_throw.ll
@@ -56,14 +56,11 @@
   ret void
 }
 
-; TODO: With updated semantics, sret could also be invisible on unwind.
-define void @test_sret(ptr nocapture noalias dereferenceable(4) sret(i32) %x) {
-; CHECK-LABEL: @test_sret(
+define void @test_noreadafterunwind(ptr nocapture noalias noreadafterunwind dereferenceable(4) %x) {
+; CHECK-LABEL: @test_noreadafterunwind(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[T:%.*]] = alloca i32, align 4
-; CHECK-NEXT:    call void @may_throw(ptr nonnull [[T]])
-; CHECK-NEXT:    [[LOAD:%.*]] = load i32, ptr [[T]], align 4
-; CHECK-NEXT:    store i32 [[LOAD]], ptr [[X:%.*]], align 4
+; CHECK-NEXT:    call void @may_throw(ptr nonnull [[X:%.*]])
 ; CHECK-NEXT:    ret void
 ;
 entry:
Index: llvm/test/Verifier/noreadafterunwind.ll
===================================================================
--- /dev/null
+++ llvm/test/Verifier/noreadafterunwind.ll
@@ -0,0 +1,7 @@
+; RUN: not llvm-as -disable-output %s 2>&1 | FileCheck %s
+
+; CHECK: Attribute 'noreadafterunwind' applied to incompatible type!
+; CHECK-NEXT: ptr @not_pointer
+define void @not_pointer(i32 noreadafterunwind %arg) {
+  ret void
+}