diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a7a941e238f3545c7f80c08dc7efa54b06674039..d30386082afc966354d45c0fbf2a1e8d927d7939 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2019-05-27  Uroš Bizjak  <ubizjak@gmail.com>
+
+	* config/i386/i386.h (STACK_SIZE_MODE): Define.
+
 2019-05-27  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/90637
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 7852c766f7707ff3fc7b6240297923c3185cd1f1..d9e8a412e6ebf2639b1fafeb926a358f73e7d85e 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -1947,6 +1947,10 @@ do {							\
 #define STACK_SAVEAREA_MODE(LEVEL)			\
   ((LEVEL) == SAVE_NONLOCAL ? (TARGET_64BIT ? TImode : DImode) : Pmode)
 
+/* Specify the machine_mode of the size increment
+   operand of an 'allocate_stack' named pattern.  */
+#define STACK_SIZE_MODE Pmode
+
 /* A C expression whose value is zero if pointers that need to be extended
    from being `POINTER_SIZE' bits wide to `Pmode' are sign-extended and
    greater then zero if they are zero-extended and less then zero if the