diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -69,6 +69,7 @@
 
 #define DEBUG_TYPE "function-attrs"
 
+STATISTIC(NumArgMemOnly, "Number of functions marked argmemonly");
 STATISTIC(NumReadNone, "Number of functions marked readnone");
 STATISTIC(NumReadOnly, "Number of functions marked readonly");
 STATISTIC(NumWriteOnly, "Number of functions marked writeonly");
@@ -1691,6 +1692,44 @@
   }
 }
 
+static bool functionArgMemOnly(const Function &F) {
+  // We can infer and propagate function attributes only when we know that the
+  // definition we'll get at link time is *exactly* the definition we see now.
+  // For more details, see GlobalValue::mayBeDerefined.
+  if (!F.hasExactDefinition())
+    return false;
+
+  // Can only analyze functions with a definition.
+  if (F.isDeclaration())
+    return false;
+
+  // If all memory accesses are to arguments, the function is argmemonly.
+  // TODO: The current implementation doesn't yet consider calls to argmemonly
+  // functions.
+  return all_of(instructions(F), [](const Instruction &I) {
+    if (!I.mayReadOrWriteMemory())
+      return true;
+    auto Loc = MemoryLocation::getOrNone(&I);
+    if (!Loc)
+      return false;
+    auto *UO = getUnderlyingObject(Loc->Ptr);
+    return UO && isa<Argument>(UO);
+  });
+}
+
+static void addArgMemOnly(const SCCNodeSet &SCCNodes,
+                          SmallSet<Function *, 8> &Changed) {
+  for (Function *F : SCCNodes) {
+    if (!F || F->doesNotAccessMemory() || F->onlyAccessesArgMemory() ||
+        !functionArgMemOnly(*F))
+      continue;
+
+    F->setOnlyAccessesArgMemory();
+    NumArgMemOnly++;
+    Changed.insert(F);
+  }
+}
+
 // Return true if this is an atomic which has an ordering stronger than
 // unordered.  Note that this is different than the predicate we use in
 // Attributor.  Here we chose to be conservative and consider monotonic
@@ -1815,6 +1854,7 @@
   inferConvergent(Nodes.SCCNodes, Changed);
   addNoReturnAttrs(Nodes.SCCNodes, Changed);
   addWillReturn(Nodes.SCCNodes, Changed);
+  addArgMemOnly(Nodes.SCCNodes, Changed);
 
   // If we have no external nodes participating in the SCC, we can deduce some
   // more precise attributes as well.
diff --git a/llvm/test/Transforms/FunctionAttrs/argmemonly.ll b/llvm/test/Transforms/FunctionAttrs/argmemonly.ll
--- a/llvm/test/Transforms/FunctionAttrs/argmemonly.ll
+++ b/llvm/test/Transforms/FunctionAttrs/argmemonly.ll
@@ -14,7 +14,7 @@
 }
 
 define i32 @test_only_read_arg(i32* %ptr) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind readonly willreturn
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nosync nounwind readonly willreturn
 ; CHECK-LABEL: @test_only_read_arg(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[L:%.*]] = load i32, i32* [[PTR:%.*]], align 4
@@ -52,7 +52,7 @@
 }
 
 define void @test_only_write_arg(i32* %ptr) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn writeonly
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nosync nounwind willreturn writeonly
 ; CHECK-LABEL: @test_only_write_arg(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    store i32 0, i32* [[PTR:%.*]], align 4
@@ -91,7 +91,7 @@
 declare i32 @fn_readnone() readnone
 
 define void @test_call_readnone(i32* %ptr) {
-; CHECK: Function Attrs: writeonly
+; CHECK: Function Attrs: argmemonly writeonly
 ; CHECK-LABEL: @test_call_readnone(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[C:%.*]] = call i32 @fn_readnone()
diff --git a/llvm/test/Transforms/FunctionAttrs/atomic.ll b/llvm/test/Transforms/FunctionAttrs/atomic.ll
--- a/llvm/test/Transforms/FunctionAttrs/atomic.ll
+++ b/llvm/test/Transforms/FunctionAttrs/atomic.ll
@@ -21,4 +21,4 @@
 }
 
 ; CHECK: attributes #0 = { mustprogress nofree norecurse nosync nounwind readnone ssp willreturn uwtable }
-; CHECK: attributes #1 = { mustprogress nofree norecurse nounwind ssp willreturn uwtable }
+; CHECK: attributes #1 = { argmemonly mustprogress nofree norecurse nounwind ssp willreturn uwtable }
diff --git a/llvm/test/Transforms/FunctionAttrs/nofree.ll b/llvm/test/Transforms/FunctionAttrs/nofree.ll
--- a/llvm/test/Transforms/FunctionAttrs/nofree.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nofree.ll
@@ -36,7 +36,7 @@
 declare void @free(i8* nocapture) local_unnamed_addr #2
 
 define i32 @_Z4foo3Pi(i32* nocapture readonly %a) local_unnamed_addr #3 {
-; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind readonly willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nosync nounwind readonly willreturn uwtable
 ; CHECK-LABEL: @_Z4foo3Pi(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[A:%.*]], align 4
diff --git a/llvm/test/Transforms/FunctionAttrs/nosync.ll b/llvm/test/Transforms/FunctionAttrs/nosync.ll
--- a/llvm/test/Transforms/FunctionAttrs/nosync.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nosync.ll
@@ -49,7 +49,7 @@
 
 ; negative case - explicit sync
 define void @test5(i8* %p) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn
 ; CHECK-LABEL: @test5(
 ; CHECK-NEXT:    store atomic i8 0, i8* [[P:%.*]] seq_cst, align 1
 ; CHECK-NEXT:    ret void
@@ -60,7 +60,7 @@
 
 ; negative case - explicit sync
 define i8 @test6(i8* %p) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn
 ; CHECK-LABEL: @test6(
 ; CHECK-NEXT:    [[V:%.*]] = load atomic i8, i8* [[P:%.*]] seq_cst, align 1
 ; CHECK-NEXT:    ret i8 [[V]]
@@ -71,7 +71,7 @@
 
 ; negative case - explicit sync
 define void @test7(i8* %p) {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn
 ; CHECK-LABEL: @test7(
 ; CHECK-NEXT:    [[TMP1:%.*]] = atomicrmw add i8* [[P:%.*]], i8 0 seq_cst, align 1
 ; CHECK-NEXT:    ret void
@@ -104,7 +104,7 @@
 
 ; atomic load with monotonic ordering
 define i32 @load_monotonic(i32* nocapture readonly %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn uwtable
 ; CHECK-LABEL: @load_monotonic(
 ; CHECK-NEXT:    [[TMP2:%.*]] = load atomic i32, i32* [[TMP0:%.*]] monotonic, align 4
 ; CHECK-NEXT:    ret i32 [[TMP2]]
@@ -115,7 +115,7 @@
 
 ; atomic store with monotonic ordering.
 define void @store_monotonic(i32* nocapture %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn uwtable
 ; CHECK-LABEL: @store_monotonic(
 ; CHECK-NEXT:    store atomic i32 10, i32* [[TMP0:%.*]] monotonic, align 4
 ; CHECK-NEXT:    ret void
@@ -127,7 +127,7 @@
 ; negative, should not deduce nosync
 ; atomic load with acquire ordering.
 define i32 @load_acquire(i32* nocapture readonly %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn uwtable
 ; CHECK-LABEL: @load_acquire(
 ; CHECK-NEXT:    [[TMP2:%.*]] = load atomic i32, i32* [[TMP0:%.*]] acquire, align 4
 ; CHECK-NEXT:    ret i32 [[TMP2]]
@@ -137,7 +137,7 @@
 }
 
 define i32 @load_unordered(i32* nocapture readonly %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind readonly willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nosync nounwind readonly willreturn uwtable
 ; CHECK-LABEL: @load_unordered(
 ; CHECK-NEXT:    [[TMP2:%.*]] = load atomic i32, i32* [[TMP0:%.*]] unordered, align 4
 ; CHECK-NEXT:    ret i32 [[TMP2]]
@@ -148,7 +148,7 @@
 
 ; atomic store with unordered ordering.
 define void @store_unordered(i32* nocapture %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nosync nounwind willreturn writeonly uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nosync nounwind willreturn writeonly uwtable
 ; CHECK-LABEL: @store_unordered(
 ; CHECK-NEXT:    store atomic i32 10, i32* [[TMP0:%.*]] unordered, align 4
 ; CHECK-NEXT:    ret void
@@ -161,7 +161,7 @@
 ; negative, should not deduce nosync
 ; atomic load with release ordering
 define void @load_release(i32* nocapture %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: nofree norecurse nounwind uwtable
+; CHECK: Function Attrs: argmemonly nofree norecurse nounwind uwtable
 ; CHECK-LABEL: @load_release(
 ; CHECK-NEXT:    store atomic volatile i32 10, i32* [[TMP0:%.*]] release, align 4
 ; CHECK-NEXT:    ret void
@@ -172,7 +172,7 @@
 
 ; negative volatile, relaxed atomic
 define void @load_volatile_release(i32* nocapture %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: nofree norecurse nounwind uwtable
+; CHECK: Function Attrs: argmemonly nofree norecurse nounwind uwtable
 ; CHECK-LABEL: @load_volatile_release(
 ; CHECK-NEXT:    store atomic volatile i32 10, i32* [[TMP0:%.*]] release, align 4
 ; CHECK-NEXT:    ret void
@@ -183,7 +183,7 @@
 
 ; volatile store.
 define void @volatile_store(i32* %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: nofree norecurse nounwind uwtable
+; CHECK: Function Attrs: argmemonly nofree norecurse nounwind uwtable
 ; CHECK-LABEL: @volatile_store(
 ; CHECK-NEXT:    store volatile i32 14, i32* [[TMP0:%.*]], align 4
 ; CHECK-NEXT:    ret void
@@ -195,7 +195,7 @@
 ; negative, should not deduce nosync
 ; volatile load.
 define i32 @volatile_load(i32* %0) norecurse nounwind uwtable {
-; CHECK: Function Attrs: mustprogress nofree norecurse nounwind willreturn uwtable
+; CHECK: Function Attrs: argmemonly mustprogress nofree norecurse nounwind willreturn uwtable
 ; CHECK-LABEL: @volatile_load(
 ; CHECK-NEXT:    [[TMP2:%.*]] = load volatile i32, i32* [[TMP0:%.*]], align 4
 ; CHECK-NEXT:    ret i32 [[TMP2]]
diff --git a/llvm/test/Transforms/FunctionAttrs/stats.ll b/llvm/test/Transforms/FunctionAttrs/stats.ll
--- a/llvm/test/Transforms/FunctionAttrs/stats.ll
+++ b/llvm/test/Transforms/FunctionAttrs/stats.ll
@@ -16,7 +16,8 @@
   ret void
 }
 
-; CHECK:      1 function-attrs - Number of arguments marked nocapture
+; CHECK:      1 function-attrs - Number of functions marked argmemonly
+; CHECK-NEXT: 1 function-attrs - Number of arguments marked nocapture
 ; CHECK-NEXT: 1 function-attrs - Number of functions marked as nofree
 ; CHECK-NEXT: 2 function-attrs - Number of functions marked as norecurse
 ; CHECK-NEXT: 2 function-attrs - Number of functions marked as nosync