diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e213db6e2a0..b09c7ce5812 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2017-09-17  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/82166
+	* config/i386/i386.c (ix86_finalize_stack_frame_flags): Properly
+	compute the minimum stack alignment.  Also update preferred stack
+	boundary for leaf functions.
+
 2017-09-16  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/82228
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fa79762a922..4f0414ffa9d 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -14257,11 +14257,12 @@ ix86_finalize_stack_frame_flags (void)
   unsigned int incoming_stack_boundary
     = (crtl->parm_stack_boundary > ix86_incoming_stack_boundary
        ? crtl->parm_stack_boundary : ix86_incoming_stack_boundary);
+  unsigned int stack_alignment
+    = (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
+       ? crtl->max_used_stack_slot_alignment
+       : crtl->stack_alignment_needed);
   unsigned int stack_realign
-    = (incoming_stack_boundary
-       < (crtl->is_leaf && !ix86_current_function_calls_tls_descriptor
-	  ? crtl->max_used_stack_slot_alignment
-	  : crtl->stack_alignment_needed));
+    = (incoming_stack_boundary < stack_alignment);
   bool recompute_frame_layout_p = false;
 
   if (crtl->stack_realign_finalized)
@@ -14306,7 +14307,9 @@ ix86_finalize_stack_frame_flags (void)
 			   HARD_FRAME_POINTER_REGNUM);
 
       /* The preferred stack alignment is the minimum stack alignment.  */
-      unsigned int stack_alignment = crtl->preferred_stack_boundary;
+      if (stack_alignment > crtl->preferred_stack_boundary)
+	stack_alignment = crtl->preferred_stack_boundary;
+
       bool require_stack_frame = false;
 
       FOR_EACH_BB_FN (bb, cfun)
@@ -14349,6 +14352,10 @@ ix86_finalize_stack_frame_flags (void)
 		= incoming_stack_boundary;
 	      crtl->stack_alignment_needed
 		= incoming_stack_boundary;
+	      /* Also update preferred_stack_boundary for leaf
+	         functions.  */
+	      crtl->preferred_stack_boundary
+		= incoming_stack_boundary;
 	    }
 	}
       else
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index d40f08e13cf..47de348eb51 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-17  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/82166
+	* gcc.target/i386/pr82166.c: New test.
+
 2017-09-17  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/82173
diff --git a/gcc/testsuite/gcc.target/i386/pr82166.c b/gcc/testsuite/gcc.target/i386/pr82166.c
new file mode 100644
index 00000000000..8bc63e15231
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr82166.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+
+void foo (void);
+int a, b, c;
+int
+main (void)
+{
+  int j;
+  for (; c;)
+    a = b;
+  for (; j;)
+    foo ();
+}