diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -224,6 +224,14 @@
   return true;
 }
 
+static bool setAlignedAllocParam(Function &F, unsigned ArgNo) {
+  if (F.hasFnAttribute(Attribute::AllocAlign)) {
+    return false;
+  }
+  F.addFnAttr(Attribute::get(F.getContext(), Attribute::AllocAlign, static_cast<uint64_t>(ArgNo+1)));
+  return true;
+}
+
 bool llvm::inferLibFuncAttributes(Module *M, StringRef Name,
                                   const TargetLibraryInfo &TLI) {
   Function *F = M->getFunction(Name);
@@ -416,6 +424,8 @@
     Changed |= setOnlyReadsMemory(F, 0);
     return Changed;
   case LibFunc_aligned_alloc:
+    Changed |= setAlignedAllocParam(F, 0);
+    LLVM_FALLTHROUGH;
   case LibFunc_valloc:
   case LibFunc_malloc:
   case LibFunc_vec_malloc:
@@ -481,6 +491,7 @@
     Changed |= setOnlyReadsMemory(F, 1);
     return Changed;
   case LibFunc_memalign:
+    Changed |= setAlignedAllocParam(F, 0);
     Changed |= setOnlyAccessesInaccessibleMemory(F);
     Changed |= setRetNoUndef(F);
     Changed |= setDoesNotThrow(F);
diff --git a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
--- a/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
+++ b/llvm/test/Transforms/InferFunctionAttrs/annotate.ll
@@ -219,7 +219,7 @@
 ; CHECK: declare x86_fp80 @acosl(x86_fp80) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare x86_fp80 @acosl(x86_fp80)
 
-; CHECK: declare noalias noundef i8* @aligned_alloc(i64 noundef, i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+; CHECK: declare noalias noundef i8* @aligned_alloc(i64 noundef, i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALIGN:#[0-9]+]]
 declare i8* @aligned_alloc(i64, i64)
 
 ; CHECK: declare double @asin(double) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
@@ -656,7 +656,7 @@
 ; CHECK: declare noalias noundef i8* @malloc(i64 noundef) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare i8* @malloc(i64)
 
-; CHECK-LINUX: declare noalias noundef i8* @memalign(i64, i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK-LINUX: declare noalias noundef i8* @memalign(i64, i64) [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALIGN:#[0-9]+]]
 declare i8* @memalign(i64, i64)
 
 ; CHECK: declare i8* @memccpy(i8* noalias writeonly, i8* noalias nocapture readonly, i32, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
@@ -1067,6 +1067,7 @@
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]] = { mustprogress nofree nounwind willreturn writeonly }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND]] = { nofree nounwind }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] = { inaccessiblememonly mustprogress nofree nounwind willreturn }
+; CHECK-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALIGN]] = { inaccessiblememonly mustprogress nofree nounwind willreturn allocalign(1) }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_READONLY_WILLRETURN]] = { mustprogress nofree nounwind readonly willreturn }
 ; CHECK-DAG: attributes [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] = { argmemonly mustprogress nofree nounwind willreturn }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_READONLY]] = { nofree nounwind readonly }