Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -880,6 +880,11 @@
 
   const Value *Object = getUnderlyingObject(Loc.Ptr);
 
+  // Stack restore is able to modify unescaped dynamic allocas. Assume it may
+  // modify them even though the alloca is not escaped.
+  if (isa<AllocaInst>(Object) && isIntrinsicCall(Call, Intrinsic::stackrestore))
+    return ModRefInfo::Mod;
+
   // Calls marked 'tail' cannot read or write allocas from the current frame
   // because the current frame might be destroyed by the time they run. However,
   // a tail call may use an alloca with byval. Calling with byval copies the
@@ -891,12 +896,6 @@
           !CI->getAttributes().hasAttrSomewhere(Attribute::ByVal))
         return ModRefInfo::NoModRef;
 
-  // Stack restore is able to modify unescaped dynamic allocas. Assume it may
-  // modify them even though the alloca is not escaped.
-  if (auto *AI = dyn_cast<AllocaInst>(Object))
-    if (!AI->isStaticAlloca() && isIntrinsicCall(Call, Intrinsic::stackrestore))
-      return ModRefInfo::Mod;
-
   // If the pointer is to a locally allocated object that does not escape,
   // then the call can not mod/ref the pointer unless the call takes the pointer
   // as an argument, and itself doesn't capture it.
Index: llvm/test/Transforms/MemCpyOpt/stackrestore.ll
===================================================================
--- llvm/test/Transforms/MemCpyOpt/stackrestore.ll
+++ llvm/test/Transforms/MemCpyOpt/stackrestore.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S -memcpyopt < %s -verify-memoryssa | FileCheck %s
+; RUN: opt -S -passes=memcpyopt -verify-memoryssa < %s | FileCheck %s --check-prefix=CHECK-TEST2
 
 ; PR40118: BasicAA didn't realize that stackrestore ends the lifetime of
 ; unescaped dynamic allocas, such as those that might come from inalloca.
@@ -80,6 +81,61 @@
   ret i32 0
 }
 
+; Test that memcpyopt does not change the final memcpy because the source
+; is an alloca that is clobbered by a call to stackrestore
+
+; Function Attrs: nobuiltin norecurse
+define dso_local void @test() {
+; CHECK-TEST2-LABEL: @test
+; CHECK-TEST2-NOT: ret void
+; CHECK-TEST2: tail call void @llvm.stackrestore(ptr %SS)
+; CHECK-TEST2: call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(56) %uglygep123, ptr noundef nonnull align 8 dereferenceable(56) %A1, i32 56, i1 false)
+; CHECK-TEST2: ret void
+entry:
+  %A1 = alloca [56 x i8], align 8
+  %SS = tail call ptr @llvm.stacksave()
+  %A2 = alloca [56 x i8], align 4
+  store i8 1, ptr %A2, align 4
+  %GEP1 = getelementptr inbounds i8, ptr %A2, i32 8
+  store i8 1, ptr %GEP1, align 4
+  %GEP2 = getelementptr inbounds i8, ptr %A2, i32 12
+  store i8 1, ptr %GEP2, align 4
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 8 dereferenceable(56) %A1, ptr noundef nonnull align 4 dereferenceable(56) %A2, i32 56, i1 false)
+  tail call void @llvm.stackrestore(ptr %SS)
+  %A3 = alloca [56 x i8], align 4
+  %uglygep123 = getelementptr i8, ptr %A3, i32 0
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(56) %uglygep123, ptr noundef nonnull align 8 dereferenceable(56) %A1, i32 56, i1 false)
+  ret void
+}
+
+; Control test: mimic the previous test but substitute different functions
+; for the intrinsics stacksave and stackrestore.  Test that memcpyopt does
+; optimize the final memcpy.
+
+; Function Attrs: nobuiltin norecurse
+define dso_local void @control() {
+; CHECK-TEST2-LABEL: @control
+; CHECK-TEST2-NOT: ret void
+; CHECK-TEST2: tail call void @useit(ptr %CSS)
+; CHECK-TEST2: call void @llvm.memcpy.p0.p0.i32(ptr align 1 %Cuglygep123, ptr align 4 %CA2, i32 56, i1 false)
+; CHECK-TEST2: ret void
+entry:
+  %CA1 = alloca [56 x i8], align 8
+  %CSS = tail call ptr @external()
+  %CA2 = alloca [56 x i8], align 4
+  store i8 1, ptr %CA2, align 4
+  %CGEP1 = getelementptr inbounds i8, ptr %CA2, i32 8
+  store i8 1, ptr %CGEP1, align 4
+  %CGEP2 = getelementptr inbounds i8, ptr %CA2, i32 12
+  store i8 1, ptr %CGEP2, align 4
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 8 dereferenceable(56) %CA1, ptr noundef nonnull align 4 dereferenceable(56) %CA2, i32 56, i1 false)
+  tail call void @useit(ptr %CSS)
+  %CA3 = alloca [56 x i8], align 4
+  %Cuglygep123 = getelementptr i8, ptr %CA3, i32 0
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(56) %Cuglygep123, ptr noundef nonnull align 8 dereferenceable(56) %CA1, i32 56, i1 false)
+  ret void
+}
+
 declare void @llvm.memcpy.p0.p0.i32(ptr nocapture writeonly, ptr nocapture readonly, i32, i1)
 declare ptr @llvm.stacksave()
 declare void @llvm.stackrestore(ptr)