c++: Shrink lambda-expr

c++: Shrink lambda-expr

[Nathan Sidwell]

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I noticed the default capture mode and the discriminator both used ints. 
  That seems excessive.  This shrinks them to 8 bits and 16 bits 
respectively.  I suppose the discriminator could use the remaining 24 
bits of an int allocation unit, if we're worried about more that 64K 
lambdas per function.  I know, users are strange :)  On a 64 bit system 
this saves 64 bits, because we also had 32 bits of padding added.

             gcc/cp/
             * cp-tree.h (struct tree_lambda_expr): Shrink
             default_capture_mode & discriminator.


-- 
Nathan Sidwell

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diff --git i/gcc/cp/cp-tree.h w/gcc/cp/cp-tree.h
index a599f3bad1c..d43c53ae29a 100644
--- i/gcc/cp/cp-tree.h
+++ w/gcc/cp/cp-tree.h
@@ -1442,8 +1442,8 @@ struct GTY (()) tree_lambda_expr
   tree extra_scope;
   vec<tree, va_gc> *pending_proxies;
   location_t locus;
-  enum cp_lambda_default_capture_mode_type default_capture_mode;
-  int discriminator;
+  enum cp_lambda_default_capture_mode_type default_capture_mode : 8;
+  short int discriminator;
 };
 
 /* Non-zero if this template specialization has access violations that