This patch adds return and simple_return patterns to the s390 backend,
which eanbles shrink-wrapping and conditional returns to be used.
Perhaps the only subtle thing is the handling of call-clobbered base
registers. The idea is to emit the initialising main_pool pattern in
both early_mach -- at the very beginning of the function -- and in the
prologue. Then, if shrink-wrapping is used, the one added by early_mach
will still be the first in the function. If shrink-wrapping isn't used
then the one added by the prologue will be the first in the function.
s390_mainpool_start then deletes whichever isn't needed.
Tested in the same way as the previous patches. OK to install?
Thanks,
Richard
gcc/
* config/s390/s390-protos.h (s390_can_use_simple_return_insn)
(s390_can_use_return_insn): Declare.
* config/s390/s390.h (EPILOGUE_USES): Define.
* config/s390/s390.c (s390_mainpool_start): Allow two main_pool
instructions.
(s390_chunkify_start): Handle return JUMP_LABELs.
(s390_early_mach): Emit a main_pool instruction on the entry edge.
(s300_set_up_by_prologue, s390_can_use_simple_return_insn)
(s390_can_use_return_insn): New functions.
(s390_fix_long_loop_prediction): Handle conditional returns.
(TARGET_SET_UP_BY_PROLOGUE): Define.
* config/s390/s390.md (ANY_RETURN): New code iterator.
(*creturn, *csimple_return, return, simple_return): New patterns.
Index: gcc/config/s390/s390-protos.h
===================================================================
--- gcc/config/s390/s390-protos.h 2014-01-31 17:20:20.520231908 +0000
+++ gcc/config/s390/s390-protos.h 2014-01-31 17:20:36.126182141 +0000
@@ -36,6 +36,8 @@ extern bool s390_check_symref_alignment
extern HOST_WIDE_INT s390_initial_elimination_offset (int, int);
extern void s390_emit_prologue (void);
extern void s390_emit_epilogue (bool);
+extern bool s390_can_use_simple_return_insn (void);
+extern bool s390_can_use_return_insn (void);
extern void s390_function_profiler (FILE *, int);
extern void s390_set_has_landing_pad_p (bool);
extern bool s390_hard_regno_mode_ok (unsigned int, enum machine_mode);
Index: gcc/config/s390/s390.h
===================================================================
--- gcc/config/s390/s390.h 2014-01-31 17:20:20.520231908 +0000
+++ gcc/config/s390/s390.h 2014-01-31 17:20:36.129182131 +0000
@@ -878,6 +878,10 @@ #define ASM_OUTPUT_ADDR_DIFF_ELT(FILE, B
fputc ('\n', (FILE));
\
} while (0)
+/* Mark the return register as used by the epilogue so that we can
+ use it in unadorned (return) and (simple_return) instructions. */
+#define EPILOGUE_USES(REGNO) ((REGNO) == RETURN_REGNUM)
+
#undef ASM_OUTPUT_FUNCTION_LABEL
#define ASM_OUTPUT_FUNCTION_LABEL(FILE, NAME, DECL) \
s390_asm_output_function_label (FILE, NAME, DECL)
Index: gcc/config/s390/s390.c
===================================================================
--- gcc/config/s390/s390.c 2014-01-31 17:20:35.405184447 +0000
+++ gcc/config/s390/s390.c 2014-01-31 17:20:36.129182131 +0000
@@ -6666,7 +6666,15 @@ s390_mainpool_start (void)
&& GET_CODE (SET_SRC (PATTERN (insn))) == UNSPEC_VOLATILE
&& XINT (SET_SRC (PATTERN (insn)), 1) == UNSPECV_MAIN_POOL)
{
- gcc_assert (!pool->pool_insn);
+ /* There might be two main_pool instructions if base_reg
+ is call-clobbered; one for shrink-wrapped code and one
+ for the rest. We want to keep the first. */
+ if (pool->pool_insn)
+ {
+ insn = PREV_INSN (insn);
+ delete_insn (NEXT_INSN (insn));
+ continue;
+ }
pool->pool_insn = insn;
}
@@ -7103,7 +7111,7 @@ s390_chunkify_start (void)
if (GET_CODE (pat) == SET)
{
rtx label = JUMP_LABEL (insn);
- if (label)
+ if (label && !ANY_RETURN_P (label))
{
if (s390_find_pool (pool_list, label)
!= s390_find_pool (pool_list, insn))
@@ -8628,6 +8636,11 @@ s390_early_mach (void)
/* Re-compute register info. */
s390_register_info ();
+ /* If we're using a base register, ensure that it is always valid for
+ the first non-prologue instruction. */
+ if (cfun->machine->base_reg)
+ emit_insn_at_entry (gen_main_pool (cfun->machine->base_reg));
+
/* Annotate all constant pool references to let the scheduler know
they implicitly use the base register. */
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
@@ -9163,6 +9176,55 @@ s390_emit_epilogue (bool sibcall)
}
}
+/* Implement TARGET_SET_UP_BY_PROLOGUE. */
+
+static void
+s300_set_up_by_prologue (hard_reg_set_container *regs)
+{
+ if (cfun->machine->base_reg
+ && !call_really_used_regs[REGNO (cfun->machine->base_reg)])
+ SET_HARD_REG_BIT (regs->set, REGNO (cfun->machine->base_reg));
+}
+
+/* Return true if the function can use simple_return to return outside
+ of a shrink-wrapped region. At present shrink-wrapping is supported
+ in all cases. */
+
+bool
+s390_can_use_simple_return_insn (void)
+{
+ return true;
+}
+
+/* Return true if the epilogue is guaranteed to contain only a return
+ instruction and if a direct return can therefore be used instead.
+ One of the main advantages of using direct return instructions
+ is that we can then use conditional returns. */
+
+bool
+s390_can_use_return_insn (void)
+{
+ int i;
+
+ if (!reload_completed)
+ return false;
+
+ if (crtl->profile)
+ return false;
+
+ if (TARGET_TPF_PROFILING)
+ return false;
+
+ for (i = 0; i < 16; i++)
+ if (cfun_gpr_save_slot (i))
+ return false;
+
+ if (cfun->machine->base_reg
+ && !call_really_used_regs[REGNO (cfun->machine->base_reg)])
+ return false;
+
+ return cfun_frame_layout.frame_size == 0;
+}
/* Return the size in bytes of a function argument of
type TYPE and/or mode MODE. At least one of TYPE or
@@ -11012,6 +11074,11 @@ s390_fix_long_loop_prediction (rtx insn)
|| GET_CODE (SET_SRC(set)) != IF_THEN_ELSE)
return false;
+ /* Skip conditional returns. */
+ if (ANY_RETURN_P (XEXP (SET_SRC (set), 1))
+ && XEXP (SET_SRC (set), 2) == pc_rtx)
+ return false;
+
label_ref = (GET_CODE (XEXP (SET_SRC (set), 1)) == LABEL_REF ?
XEXP (SET_SRC (set), 1) : XEXP (SET_SRC (set), 2));
@@ -12156,6 +12223,9 @@ #define TARGET_ATTRIBUTE_TABLE s390_attr
#undef TARGET_CAN_INLINE_P
#define TARGET_CAN_INLINE_P s390_can_inline_p
+#undef TARGET_SET_UP_BY_PROLOGUE
+#define TARGET_SET_UP_BY_PROLOGUE s300_set_up_by_prologue
+
struct gcc_target targetm = TARGET_INITIALIZER;
#include "gt-s390.h"
Index: gcc/config/s390/s390.md
===================================================================
--- gcc/config/s390/s390.md 2014-01-31 17:20:20.520231908 +0000
+++ gcc/config/s390/s390.md 2014-01-31 17:20:36.131182125 +0000
@@ -598,6 +598,9 @@ (define_mode_attr bfend [(DI "e") (SI
;; In place of GET_MODE_BITSIZE (<MODE>mode)
(define_mode_attr bitsize [(DI "64") (SI "32") (HI "16") (QI "8")])
+;; Allow return and simple_return to be defined from a single template.
+(define_code_iterator ANY_RETURN [return simple_return])
+
;;
;;- Compare instructions.
;;
@@ -8079,6 +8082,18 @@ (define_insn "*cjump_long"
(set_attr "type" "branch")
(set_attr "atype" "agen")])
+;; A conditional return instruction.
+(define_insn "*c<code>"
+ [(set (pc)
+ (if_then_else
+ (match_operator 0 "s390_comparison" [(reg CC_REGNUM) (const_int 0)])
+ (ANY_RETURN)
+ (pc)))]
+ "s390_can_use_<code>_insn ()"
+ "b%C0r\t%%r14"
+ [(set_attr "op_type" "RR")
+ (set_attr "type" "branch")
+ (set_attr "atype" "agen")])
;;
;;- Negated conditional jump instructions.
@@ -9662,6 +9677,15 @@ (define_expand "sibcall_epilogue"
""
"s390_emit_epilogue (true); DONE;")
+;; A direct return instruction, without using an epilogue.
+(define_insn "<code>"
+ [(ANY_RETURN)]
+ "s390_can_use_<code>_insn ()"
+ "br\t%%r14"
+ [(set_attr "op_type" "RR")
+ (set_attr "type" "jsr")
+ (set_attr "atype" "agen")])
+
(define_insn "*return"
[(return)
(use (match_operand 0 "register_operand" "a"))]
