diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -2222,6 +2222,10 @@
 
 Enable optimizations based on the strict rules for overwriting polymorphic C++ objects
 
+.. option:: -fstrict-pointer-alignment, -fno-strict-pointer-alignment
+
+Enable optimizations based on the strict rules for pointer alignment
+
 .. option:: -fstruct-path-tbaa, -fno-struct-path-tbaa
 
 .. option:: -fsymbol-partition=<arg>
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -54,6 +54,10 @@
   to allow codebases to be cleaned up in preparation for this optimization,
   to avoid miscompiles.
 
+- Clang now assumes that all function pointer arguments are properly aligned,
+  and optimizes on that. A new ``-fstrict-pointer-alignment`` flag was
+  introduces (default on), which guards these new optimizations.
+
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -1669,6 +1669,12 @@
    modules where it isn't necessary. It causes more inline virtual functions
    to be emitted.
 
+.. option:: -fstrict-pointer-alignment
+
+   Enable optimizations based on the strict rules for pointer alignment.
+   This currently only affects function pointer arguments, and only controls
+   UBSan behaviour, no optimizations are currently performed based on it.
+
 .. option:: -fno-assume-sane-operator-new
 
    Don't assume that the C++'s new operator is sane.
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -261,6 +261,7 @@
 CODEGENOPT(FineGrainedBitfieldAccesses, 1, 0) ///< Enable fine-grained bitfield accesses.
 CODEGENOPT(StrictEnums       , 1, 0) ///< Optimize based on strict enum definition.
 CODEGENOPT(StrictVTablePointers, 1, 0) ///< Optimize based on the strict vtable pointers
+CODEGENOPT(StrictPointerAlignment, 1, 1) ///< Optimize based on the strict pointer alignment rules
 CODEGENOPT(TimePasses        , 1, 0) ///< Set when -ftime-report or -ftime-report= is enabled.
 CODEGENOPT(TimePassesPerRun  , 1, 0) ///< Set when -ftime-report=per-pass-run is enabled.
 CODEGENOPT(TimeTrace         , 1, 0) ///< Set when -ftime-trace is enabled.
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2446,6 +2446,11 @@
   PosFlag<SetTrue, [CC1Option], "Enable optimizations based on the strict rules for"
             " overwriting polymorphic C++ objects">,
   NegFlag<SetFalse>>;
+defm strict_pointer_alignment : BoolFOption<"strict-pointer-alignment",
+  CodeGenOpts<"StrictPointerAlignment">, DefaultFalse,
+  NegFlag<SetFalse, [CC1Option], "Disable">,
+  PosFlag<SetTrue,  [CC1Option], "Enable">,
+  BothFlags<[], " optimizations based on the strict rules for pointer alignmen">>;
 def fstrict_overflow : Flag<["-"], "fstrict-overflow">, Group<f_Group>;
 def fsyntax_only : Flag<["-"], "fsyntax-only">,
   Flags<[NoXarchOption,CoreOption,CC1Option,FC1Option]>, Group<Action_Group>;
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2446,6 +2446,17 @@
       }
     }
 
+    if (getCodeGenOpts().StrictPointerAlignment) {
+      if (const auto *PtrTy = ParamType->getAs<PointerType>()) {
+        QualType PTy = PtrTy->getPointeeType();
+        if (PTy->isObjectType()) {
+          llvm::Align Alignment =
+              getNaturalPointeeTypeAlignment(ParamType).getAsAlign();
+          Attrs.addAlignmentAttr(Alignment);
+        }
+      }
+    }
+
     switch (FI.getExtParameterInfo(ArgNo).getABI()) {
     case ParameterABI::Ordinary:
       break;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4872,6 +4872,10 @@
                    options::OPT_fno_force_emit_vtables,
                    false))
     CmdArgs.push_back("-fforce-emit-vtables");
+  if (Args.hasFlag(options::OPT_fstrict_pointer_alignment,
+                   options::OPT_fno_strict_pointer_alignment,
+                   !RawTriple.isOSDarwin()))
+    CmdArgs.push_back("-fstrict-pointer-alignment");
   if (!Args.hasFlag(options::OPT_foptimize_sibling_calls,
                     options::OPT_fno_optimize_sibling_calls))
     CmdArgs.push_back("-mdisable-tail-calls");