* invoke.texi (-fstrict-aliasing): Document.

	* rtl.texi (MEM_ALIAS_SET): Document.
	* flags.h (flag_strict_aliasing): Declare.
	* toplev.c (flag_strict_aliasing): Define.
	(f_options): Add -strict-aliasing.
	(main): Set flag_strict_aliasing if -O2 or higher.
	* tree.h (tree_type): Add alias_set field.
	(TYPE_ALIAS_SET): New macro.
	(TYPE_ALIAS_SET_KNOWN_P): Likewise.
	(get_alias_set): Declare.
	* tree.c (lang_get_alias_set): Define.
	(make_node): Initialize TYPE_ALIAS_SET.
	(get_alias_set): New function.
	* print-tree.c (print_node): Dump the alias set for a type.
	* c-tree.h (c_get_alias_set): Declare.
	* c-common.c (c_get_alias_set): New function.
	* c-decl.c (init_decl_processing): Set lang_get_alias_set.
	* expr.c (protect_from_queue): Propogage alias sets.
	(expand_assignment): Calculate alias set for new MEMs.
	(expand_expr): Likewise.
	* function.c (put_var_into_stack): Likewise.
	(put_reg_into_stack): Likewise.
	(gen_mem_addressof): Likewise.
	(assign_parms): Likewise.
	* stmt.c (expand_decl): Likewise.
	* varasm.c (make_decl_rtl): Eliminate redundant clearing of
	DECL_RTL.  Calculate alias set for new MEMs.
	* rtl.def (REG): Add dummy operand.
	(MEM): Add extra operand to store the MEM_ALIAS_SET.
	* rtl.h (MEM_ALIAS_SET): New macro.
	(gen_rtx_MEM): Declare.
	* emit-rtl.c (gen_rtx_MEM): New function.
	* gengenrtl.c (sepcial_rtx): Make MEMs special.
	* alias.c (CHECK_ALIAS_SETS_FOR_CONSISTENCY): New macro.
	(DIFFERENT_ALIAS_SETS_P): Likewise.
	(canon_rtx): Propogate the alias set to the new MEM.
	(true_dependence): Check the alias sets.
	(anti_dependence): Likewise.
	(output_dependence): Likewise.
	* explow.c (stabilize): Progoate alias sets.
	* integrate.c (copy_rtx_and_substitute): Likewise.
	* final.c (alter_subreg): Make sure not to leave MEM_IN_STRUCT_P
	in an unpredictable state.  Propogate alias sets.
	* reload1.c (reload): Clear MEM_ALIAS_SET for new MEMs about which
	we have no alias information.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@20719 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 15 insertions, 7 deletions

diff --git a/gcc/rtl.def b/gcc/rtl.def
index e219e87c042..a00d3f1d7c5 100644
--- a/gcc/rtl.def
+++ b/gcc/rtl.def
@@ -537,10 +537,16 @@ DEF_RTL_EXPR(CONST, "const", "e", 'o')
    by a SET whose first operand is (PC).  */
 DEF_RTL_EXPR(PC, "pc", "", 'o')
 
-/* A register.  The "operand" is the register number, accessed
-   with the REGNO macro.  If this number is less than FIRST_PSEUDO_REGISTER
-   than a hardware register is being referred to.  */
-DEF_RTL_EXPR(REG, "reg", "i", 'o')
+/* A register.  The "operand" is the register number, accessed with
+   the REGNO macro.  If this number is less than FIRST_PSEUDO_REGISTER
+   than a hardware register is being referred to.  The second operand
+   doesn't really exist.  Unfortunately, however, the compiler
+   implicitly assumes that a REG can be transformed in place into a
+   MEM, and therefore that a REG is at least as big as a MEM.  To
+   avoid this memory overhead, which is likely to be substantial,
+   search for uses of PUT_CODE that turn REGs into MEMs, and fix them
+   somehow.  Then, the trailing `0' can be removed here.  */
+DEF_RTL_EXPR(REG, "reg", "i0", 'o')
 
 /* A scratch register.  This represents a register used only within a
    single insn.  It will be turned into a REG during register allocation
@@ -578,9 +584,11 @@ DEF_RTL_EXPR(STRICT_LOW_PART, "strict_low_part", "e", 'x')
    in DECL_RTLs and during RTL generation, but not in the insn chain.  */
 DEF_RTL_EXPR(CONCAT, "concat", "ee", 'o')
 
-/* A memory location; operand is the address.
-   Can be nested inside a VOLATILE.  */
-DEF_RTL_EXPR(MEM, "mem", "e", 'o')
+/* A memory location; operand is the address.  Can be nested inside a
+   VOLATILE.  The second operand is the alias set to which this MEM
+   belongs.  We use `0' instead of `i' for this field so that the
+   field need not be specified in machine descriptions.  */
+DEF_RTL_EXPR(MEM, "mem", "e0", 'o')
 
 /* Reference to an assembler label in the code for this function.
    The operand is a CODE_LABEL found in the insn chain.