Index: llvm/include/llvm/Transforms/IPO/Attributor.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/Attributor.h
+++ llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -103,6 +103,7 @@
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/CGSCCPassManager.h"
 #include "llvm/Analysis/CallGraph.h"
+#include "llvm/Analysis/InlineCost.h"
 #include "llvm/Analysis/LazyCallGraph.h"
 #include "llvm/Analysis/MustExecute.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
@@ -1704,7 +1705,7 @@
     }
 
     bool IsFnInterface = IRP.isFnInterfaceKind();
-    const Function *FnScope = IRP.getAnchorScope();
+    Function *FnScope = IRP.getAnchorScope();
     // TODO: Not all attributes require an exact definition. Find a way to
     //       enable deduction for some but not all attributes in case the
     //       definition might be changed at runtime, see also
@@ -1712,8 +1713,16 @@
     // TODO: We could always determine abstract attributes and if sufficient
     //       information was found we could duplicate the functions that do not
     //       have an exact definition.
-    if (IsFnInterface && (!FnScope || !FnScope->hasExactDefinition()))
+    if (IsFnInterface && (!FnScope || !FnScope->hasExactDefinition())) {
+      if (FnScope && FnScope->hasFnAttribute(Attribute::AlwaysInline)) {
+        // check if it is OK to inline, if so, do fix-point analysis for the
+        // function
+        InlineResult IsInlineOK = isInlineViable(*FnScope);
+        if (IsInlineOK.isSuccess())
+          return;
+      }
       this->getState().indicatePessimisticFixpoint();
+    }
   }
 
   /// See AbstractAttribute::manifest(...).
@@ -2748,7 +2757,8 @@
   /// Return an assumed constant for the assocaited value a program point \p
   /// CtxI.
   Optional<ConstantInt *>
-  getAssumedConstantInt(Attributor &A, const Instruction *CtxI = nullptr) const {
+  getAssumedConstantInt(Attributor &A,
+                        const Instruction *CtxI = nullptr) const {
     ConstantRange RangeV = getAssumedConstantRange(A, CtxI);
     if (auto *C = RangeV.getSingleElement())
       return cast<ConstantInt>(
Index: llvm/test/Transforms/Attributor/alwaysinline.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Attributor/alwaysinline.ll
@@ -0,0 +1,90 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -attributor -attributor-disable=false -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefix=CHECK
+;
+; When a function is marked `alwaysinline` and is able to be inlined,
+; we can IPO its boundaries
+
+; The function can be removed safely because it has external linkage
+; so this will be inlined, although the function is not exactly
+; defined.
+
+; CHECK: Function Attrs: alwaysinline nofree nosync nounwind readnone
+define linkonce void @inner1() alwaysinline {
+; CHECK-LABEL: @inner1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret void
+;
+entry:
+  ret void
+}
+
+; CHECK: Function Attrs: nofree nosync nounwind
+define void @outer1() {
+; CHECK-LABEL: @outer1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret void
+;
+entry:
+  call void @inner1()
+  ret void
+}
+
+; The function is not alwaysinline and is external
+; so it will be analyzed
+; CHECK: Function Attrs: nofree nosync nounwind readnone willreturn
+define i32 @inner2() {
+; CHECK-LABEL: @inner2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret i32 1
+;
+entry:
+  ret i32 1
+}
+
+; CHECK: Function Attrs: nofree nosync nounwind readnone willreturn
+define i32 @outer2() {
+; CHECK-LABEL: @outer2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret i32 1
+;
+entry:
+  %r = call i32 @inner2() alwaysinline
+  ret i32 %r
+}
+
+; This function cannot be inlined although it is marked alwaysinline
+; alwaysinline nofree nosync nounwind readnone
+; CHECK: Function Attrs:
+; CHECK-NOT: nofree nosync nounwind readnone
+define linkonce i32 @inner3(i8* %addr) alwaysinline {
+; CHECK-LABEL: @inner3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    indirectbr i8* [[ADDR:%.*]], [label [[ONE:%.*]], label %two]
+; CHECK:       one:
+; CHECK-NEXT:    ret i32 42
+; CHECK:       two:
+; CHECK-NEXT:    ret i32 44
+;
+entry:
+  indirectbr i8* %addr, [ label %one, label %two ]
+
+one:
+  ret i32 42
+
+two:
+  ret i32 44
+}
+
+; CHECK-NOT: Function Attrs:
+define i32 @outer3(i32 %x) {
+; CHECK-LABEL: @outer3(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 42
+; CHECK-NEXT:    [[ADDR:%.*]] = select i1 [[CMP]], i8* blockaddress(@inner3, [[ONE:%.*]]), i8* blockaddress(@inner3, [[TWO:%.*]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @inner3(i8* [[ADDR]])
+; CHECK-NEXT:    ret i32 [[CALL]]
+;
+  %cmp = icmp slt i32 %x, 42
+  %addr = select i1 %cmp, i8* blockaddress(@inner3, %one), i8* blockaddress(@inner3, %two)
+  %call = call i32 @inner3(i8* %addr)
+  ret i32 %call
+}