Index: llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
===================================================================
--- llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -450,7 +450,7 @@
 /// Determine that this argument is safe to promote, and find the argument
 /// parts it can be promoted into.
 static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
-                         unsigned MaxElements, bool IsSelfRecursive,
+                         unsigned MaxElements, bool IsRecursive,
                          SmallVectorImpl<OffsetAndArgPart> &ArgPartsVec) {
   // Quick exit for unused arguments
   if (Arg->use_empty())
@@ -497,9 +497,9 @@
     if (Size.isScalable())
       return false;
 
-    // If this is a self-recursive function and one of the types is a pointer,
+    // If this is a recursive function and one of the types is a pointer,
     // then promoting it might lead to recursive promotion.
-    if (IsSelfRecursive && Ty->isPointerTy())
+    if (IsRecursive && Ty->isPointerTy())
       return false;
 
     int64_t Off = Offset.getSExtValue();
@@ -756,7 +756,7 @@
                  unsigned MaxElements,
                  Optional<function_ref<void(CallBase &OldCS, CallBase &NewCS)>>
                      ReplaceCallSite,
-                 const TargetTransformInfo &TTI) {
+                 const TargetTransformInfo &TTI, bool IsRecursive) {
   // Don't perform argument promotion for naked functions; otherwise we can end
   // up removing parameters that are seemingly 'not used' as they are referred
   // to in the assembly.
@@ -790,8 +790,7 @@
 
   // Second check: make sure that all callers are direct callers.  We can't
   // transform functions that have indirect callers.  Also see if the function
-  // is self-recursive and check that target features are compatible.
-  bool isSelfRecursive = false;
+  // is self-recursive.
   for (Use &U : F->uses()) {
     CallBase *CB = dyn_cast<CallBase>(U.getUser());
     // Must be a direct call.
@@ -803,7 +802,7 @@
       return nullptr;
 
     if (CB->getParent()->getParent() == F)
-      isSelfRecursive = true;
+      IsRecursive = true;
   }
 
   // Can't change signature of musttail caller
@@ -875,7 +874,7 @@
 
     // Otherwise, see if we can promote the pointer to its value.
     SmallVector<OffsetAndArgPart, 4> ArgParts;
-    if (findArgParts(PtrArg, DL, AAR, MaxElements, isSelfRecursive, ArgParts)) {
+    if (findArgParts(PtrArg, DL, AAR, MaxElements, IsRecursive, ArgParts)) {
       SmallVector<Type *, 4> Types;
       for (const auto &Pair : ArgParts)
         Types.push_back(Pair.second.Ty);
@@ -905,6 +904,7 @@
     FunctionAnalysisManager &FAM =
         AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
 
+    bool IsRecursive = C.size() > 1;
     for (LazyCallGraph::Node &N : C) {
       Function &OldF = N.getFunction();
 
@@ -916,8 +916,8 @@
       };
 
       const TargetTransformInfo &TTI = FAM.getResult<TargetIRAnalysis>(OldF);
-      Function *NewF =
-          promoteArguments(&OldF, AARGetter, MaxElements, None, TTI);
+      Function *NewF = promoteArguments(&OldF, AARGetter, MaxElements, None,
+                                        TTI, IsRecursive);
       if (!NewF)
         continue;
       LocalChange = true;
@@ -1018,6 +1018,7 @@
   do {
     LocalChange = false;
     // Attempt to promote arguments from all functions in this SCC.
+    bool IsRecursive = SCC.size() > 1;
     for (CallGraphNode *OldNode : SCC) {
       Function *OldF = OldNode->getFunction();
       if (!OldF)
@@ -1034,8 +1035,9 @@
 
       const TargetTransformInfo &TTI =
           getAnalysis<TargetTransformInfoWrapperPass>().getTTI(*OldF);
-      if (Function *NewF = promoteArguments(OldF, AARGetter, MaxElements,
-                                            {ReplaceCallSite}, TTI)) {
+      if (Function *NewF =
+              promoteArguments(OldF, AARGetter, MaxElements, {ReplaceCallSite},
+                               TTI, IsRecursive)) {
         LocalChange = true;
 
         // Update the call graph for the newly promoted function.
Index: llvm/test/Transforms/ArgumentPromotion/pr42028-recursion.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/ArgumentPromotion/pr42028-recursion.ll
@@ -0,0 +1,54 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
+; RUN: opt -S < %s -argpromotion | FileCheck %s
+
+; This shouldn't get infinitely promoted.
+
+%S = type { %S* }
+
+define i32 @test_inf_promote_caller(i32 %arg) {
+; CHECK-LABEL: define {{[^@]+}}@test_inf_promote_caller
+; CHECK-SAME: (i32 [[ARG:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[TMP:%.*]] = alloca [[S:%.*]], align 8
+; CHECK-NEXT:    [[TMP1:%.*]] = alloca [[S]], align 8
+; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @test_inf_promote_callee(%S* [[TMP]], %S* [[TMP1]])
+; CHECK-NEXT:    ret i32 0
+;
+bb:
+  %tmp = alloca %S
+  %tmp1 = alloca %S
+  %tmp2 = call i32 @test_inf_promote_callee(%S* %tmp, %S* %tmp1)
+  ret i32 0
+}
+
+define internal i32 @test_inf_promote_callee(%S* %arg, %S* %arg1) {
+; CHECK-LABEL: define {{[^@]+}}@test_inf_promote_callee
+; CHECK-SAME: (%S* [[ARG:%.*]], %S* [[ARG1:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[TMP:%.*]] = getelementptr [[S:%.*]], %S* [[ARG1]], i32 0, i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = load %S*, %S** [[TMP]], align 8
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr [[S]], %S* [[ARG]], i32 0, i32 0
+; CHECK-NEXT:    [[TMP4:%.*]] = load %S*, %S** [[TMP3]], align 8
+; CHECK-NEXT:    [[TMP5:%.*]] = call i32 @test_inf_promote_callee2(%S* [[TMP4]], %S* [[TMP2]])
+; CHECK-NEXT:    ret i32 0
+;
+bb:
+  %tmp = getelementptr %S, %S* %arg1, i32 0, i32 0
+  %tmp2 = load %S*, %S** %tmp
+  %tmp3 = getelementptr %S, %S* %arg, i32 0, i32 0
+  %tmp4 = load %S*, %S** %tmp3
+  %tmp5 = call i32 @test_inf_promote_callee2(%S* %tmp4, %S* %tmp2)
+  ret i32 0
+}
+
+define internal i32 @test_inf_promote_callee2(%S* %arg, %S* %arg1) {
+; CHECK-LABEL: define {{[^@]+}}@test_inf_promote_callee2
+; CHECK-SAME: (%S* [[ARG:%.*]], %S* [[ARG1:%.*]]) {
+; CHECK-NEXT:    [[R:%.*]] = call i32 @test_inf_promote_callee(%S* [[ARG]], %S* [[ARG1]])
+; CHECK-NEXT:    ret i32 0
+;
+  %r = call i32 @test_inf_promote_callee(%S* %arg, %S* %arg1)
+  ret i32 0
+}
+
+declare i32 @wibble(...)