Index: include/llvm/IR/Attributes.td
===================================================================
--- include/llvm/IR/Attributes.td
+++ include/llvm/IR/Attributes.td
@@ -235,3 +235,4 @@
 def : MergeRule<"adjustCallerSSPLevel">;
 def : MergeRule<"adjustCallerStackProbes">;
 def : MergeRule<"adjustCallerStackProbeSize">;
+def : MergeRule<"adjustMinLegalVectorWidth">;
Index: lib/IR/Attributes.cpp
===================================================================
--- lib/IR/Attributes.cpp
+++ lib/IR/Attributes.cpp
@@ -1682,6 +1682,33 @@
   }
 }
 
+/// If the inlined function defines a min legal vector width, then ensure
+/// the calling function has the same or larger min legal vector width. This
+/// function is called after the inlining decision has been made so we have to
+/// merge the attribute this way. Heuristics that would use
+/// min-legal-vector-width to determine inline compatibility would need to be
+/// handled as part of inline cost analysis.
+static void
+adjustMinLegalVectorWidth(Function &Caller, const Function &Callee) {
+  if (Callee.hasFnAttribute("min-legal-vector-width")) {
+    uint64_t CalleeVectorWidth;
+    Callee.getFnAttribute("min-legal-vector-width")
+          .getValueAsString()
+          .getAsInteger(0, CalleeVectorWidth);
+    if (Caller.hasFnAttribute("min-legal-vector-width")) {
+      uint64_t CallerVectorWidth;
+      Caller.getFnAttribute("min-legal-vector-width")
+            .getValueAsString()
+            .getAsInteger(0, CallerVectorWidth);
+      if (CallerVectorWidth < CalleeVectorWidth) {
+        Caller.addFnAttr(Callee.getFnAttribute("min-legal-vector-width"));
+      }
+    } else {
+      Caller.addFnAttr(Callee.getFnAttribute("min-legal-vector-width"));
+    }
+  }
+}
+
 #define GET_ATTR_COMPAT_FUNC
 #include "AttributesCompatFunc.inc"
 
Index: test/Transforms/Inline/inline-min-legal-vector-width.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/inline-min-legal-vector-width.ll
@@ -0,0 +1,29 @@
+; RUN: opt %s -inline -S | FileCheck %s
+
+define internal void @innerSmall() "min-legal-vector-width"="128" {
+  ret void
+}
+
+define internal void @innerLarge() "min-legal-vector-width"="512" {
+  ret void
+}
+
+define void @outerNoAttribute() {
+  call void @innerLarge()
+  ret void
+}
+
+define void @outerConflictingAttributeSmall() "min-legal-vector-width"="128" {
+  call void @innerLarge()
+  ret void
+}
+
+define void @outerConflictingAttributeLarge() "min-legal-vector-width"="512" {
+  call void @innerSmall()
+  ret void
+}
+
+; CHECK: define void @outerNoAttribute() #0
+; CHECK: define void @outerConflictingAttributeSmall() #0
+; CHECK: define void @outerConflictingAttributeLarge() #0
+; CHECK: attributes #0 = { "min-legal-vector-width"="512" }