This patch merges the rs6000 stack_tie and frame_tie rtl, so that we
now should use a tie insn that mentions all base regs involved in
register saves and restores. That should avoid any alias analysis
problems eg. http://gcc.gnu.org/ml/gcc-patches/2011-11/msg01156.html.
I chose to put the regs of interest on the destination of the fake
set, rather than in the source as is currently done, because I figure
that relying on the compiler to not reorder reads is fragile. Here's
an example of the new stack tie:
(set (mem:BLK (unspec:SI [(reg:SI 1) (reg:SI 12)] UNSPEC_TIE))
(const_int 0))
Some notes:
- I tried putting the mem on both source and destination of the set,
but that runs afoul of rtl dead code elimination.
- The rs6000_emit_epilogue places that called gen_frame_tie and
gen_stack_tie both used alias set 0 mems. I believe this was
unnecessarily restrictive.
- CODE_FOR_stack_tie is mentioned in rs6000.c but not
CODE_FOR_frame_tie. Removing frame_tie fixes this sched bug too.
Bootstrapped and regression tested powerpc-linux with usual -O2
BOOT_CFLAGS and also -Os, and testcases from pr44199, pr30282, pr52828,
the url above and http://gcc.gnu.org/ml/gcc/2011-03/msg00123.html
examined for sanity. OK to apply?
PR target/52828
* config/rs6000/rs6000.c (rs6000_emit_stack_tie): Rewrite with
tie regs on destination of set. Delete forward declaration.
(rs6000_emit_stack_reset): Update rs6000_emit_stack_tie calls.
(rs6000_emit_prologue): Likewise.
(rs6000_emit_epilogue): Likewise. Use in place of gen_frame_tie
and gen_stack_tie.
* config/rs6000/predicates.md (tie_operand): New.
* config/rs6000/rs6000.md (restore_stack_block): Generate new
stack tie rtl.
(restore_stack_nonlocal): Likewise.
(stack_tie): Update.
(frame_tie): Delete.
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c (revision 185830)
+++ gcc/config/rs6000/rs6000.c (working copy)
@@ -925,7 +925,6 @@ static const char *rs6000_invalid_within_doloop (c
static bool rs6000_legitimate_address_p (enum machine_mode, rtx, bool);
static bool rs6000_debug_legitimate_address_p (enum machine_mode, rtx, bool);
static rtx rs6000_generate_compare (rtx, enum machine_mode);
-static void rs6000_emit_stack_tie (void);
static bool spe_func_has_64bit_regs_p (void);
static rtx gen_frame_mem_offset (enum machine_mode, rtx, int);
static unsigned rs6000_hash_constant (rtx);
@@ -18517,12 +18516,28 @@ rs6000_aix_asm_output_dwarf_table_ref (char * fram
and the change to the stack pointer. */
static void
-rs6000_emit_stack_tie (void)
+rs6000_emit_stack_tie (rtx fp, bool hard_frame_needed)
{
- rtx mem = gen_frame_mem (BLKmode,
- gen_rtx_REG (Pmode, STACK_POINTER_REGNUM));
+ rtx u;
+ rtvec p;
+ int i;
- emit_insn (gen_stack_tie (mem));
+ if (REGNO (fp) == STACK_POINTER_REGNUM
+ || (hard_frame_needed
+ && REGNO (fp) == HARD_FRAME_POINTER_REGNUM))
+ fp = NULL_RTX;
+
+ p = rtvec_alloc (1 + hard_frame_needed + (fp != NULL_RTX));
+
+ i = 0;
+ RTVEC_ELT (p, i++) = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
+ if (hard_frame_needed)
+ RTVEC_ELT (p, i++) = gen_rtx_REG (Pmode, HARD_FRAME_POINTER_REGNUM);
+ if (fp != NULL_RTX)
+ RTVEC_ELT (p, i++) = fp;
+ u = gen_rtx_UNSPEC (Pmode, p, UNSPEC_TIE);
+
+ emit_insn (gen_stack_tie (gen_frame_mem (BLKmode, u)));
}
/* Emit the correct code for allocating stack space, as insns.
@@ -19142,7 +19157,7 @@ rs6000_emit_stack_reset (rs6000_stack_t *info,
|| (TARGET_SPE_ABI
&& info->spe_64bit_regs_used != 0
&& info->first_gp_reg_save != 32))
- rs6000_emit_stack_tie ();
+ rs6000_emit_stack_tie (frame_reg_rtx, frame_pointer_needed);
if (frame_reg_rtx != sp_reg_rtx)
{
@@ -19362,7 +19377,7 @@ rs6000_emit_prologue (void)
}
rs6000_emit_allocate_stack (info->total_size, copy_reg);
if (frame_reg_rtx != sp_reg_rtx)
- rs6000_emit_stack_tie ();
+ rs6000_emit_stack_tie (frame_reg_rtx, false);
}
/* Handle world saves specially here. */
@@ -19866,7 +19881,7 @@ rs6000_emit_prologue (void)
sp_offset = info->total_size;
rs6000_emit_allocate_stack (info->total_size, copy_reg);
if (frame_reg_rtx != sp_reg_rtx)
- rs6000_emit_stack_tie ();
+ rs6000_emit_stack_tie (frame_reg_rtx, false);
}
/* Set frame pointer, if needed. */
@@ -20437,13 +20452,7 @@ rs6000_emit_epilogue (int sibcall)
/* Prevent reordering memory accesses against stack pointer restore. */
else if (cfun->calls_alloca
|| offset_below_red_zone_p (-info->total_size))
- {
- rtx mem1 = gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx);
- rtx mem2 = gen_rtx_MEM (BLKmode, sp_reg_rtx);
- MEM_NOTRAP_P (mem1) = 1;
- MEM_NOTRAP_P (mem2) = 1;
- emit_insn (gen_frame_tie (mem1, mem2));
- }
+ rs6000_emit_stack_tie (frame_reg_rtx, true);
insn = emit_insn (gen_add3_insn (frame_reg_rtx, hard_frame_pointer_rtx,
GEN_INT (info->total_size)));
@@ -20456,11 +20465,7 @@ rs6000_emit_epilogue (int sibcall)
/* Prevent reordering memory accesses against stack pointer restore. */
if (cfun->calls_alloca
|| offset_below_red_zone_p (-info->total_size))
- {
- rtx mem = gen_rtx_MEM (BLKmode, sp_reg_rtx);
- MEM_NOTRAP_P (mem) = 1;
- emit_insn (gen_stack_tie (mem));
- }
+ rs6000_emit_stack_tie (frame_reg_rtx, false);
insn = emit_insn (gen_add3_insn (sp_reg_rtx, sp_reg_rtx,
GEN_INT (info->total_size)));
sp_offset = 0;
Index: gcc/config/rs6000/predicates.md
===================================================================
--- gcc/config/rs6000/predicates.md (revision 185830)
+++ gcc/config/rs6000/predicates.md (working copy)
@@ -1451,3 +1451,11 @@
return 1;
})
+
+;; Return 1 if OP is a stack tie operand.
+(define_predicate "tie_operand"
+ (match_code "mem")
+{
+ return (GET_CODE (XEXP (op, 0)) == UNSPEC
+ && XINT (XEXP (op, 0), 1) == UNSPEC_TIE);
+})
Index: gcc/config/rs6000/rs6000.md
===================================================================
--- gcc/config/rs6000/rs6000.md (revision 185830)
+++ gcc/config/rs6000/rs6000.md (working copy)
@@ -11989,17 +11989,20 @@
(define_expand "restore_stack_block"
[(set (match_dup 2) (match_dup 3))
(set (match_dup 4) (match_dup 2))
- (set (match_dup 5) (unspec:BLK [(match_dup 5)] UNSPEC_TIE))
+ (set (match_dup 5) (const_int 0))
(set (match_operand 0 "register_operand" "")
(match_operand 1 "register_operand" ""))]
""
"
{
+ rtx u;
+
operands[1] = force_reg (Pmode, operands[1]);
operands[2] = gen_reg_rtx (Pmode);
operands[3] = gen_frame_mem (Pmode, operands[0]);
operands[4] = gen_frame_mem (Pmode, operands[1]);
- operands[5] = gen_frame_mem (BLKmode, operands[0]);
+ u = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, operands[0]), UNSPEC_TIE);
+ operands[5] = gen_frame_mem (BLKmode, u);
}")
(define_expand "save_stack_nonlocal"
@@ -12022,12 +12025,13 @@
[(set (match_dup 2) (match_operand 1 "memory_operand" ""))
(set (match_dup 3) (match_dup 4))
(set (match_dup 5) (match_dup 2))
- (set (match_dup 6) (unspec:BLK [(match_dup 6)] UNSPEC_TIE))
+ (set (match_dup 6) (const_int 0))
(set (match_operand 0 "register_operand" "") (match_dup 3))]
""
"
{
int units_per_word = (TARGET_32BIT) ? 4 : 8;
+ rtx u;
/* Restore the backchain from the first word, sp from the second. */
operands[2] = gen_reg_rtx (Pmode);
@@ -12035,7 +12039,8 @@
operands[1] = adjust_address_nv (operands[1], Pmode, 0);
operands[4] = adjust_address_nv (operands[1], Pmode, units_per_word);
operands[5] = gen_frame_mem (Pmode, operands[3]);
- operands[6] = gen_frame_mem (BLKmode, operands[0]);
+ u = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, operands[0]), UNSPEC_TIE);
+ operands[6] = gen_frame_mem (BLKmode, u);
}")
;; TOC register handling.
@@ -15899,25 +15904,15 @@
[(set_attr "type" "branch")
(set_attr "length" "4")])
-; These are to explain that changes to the stack pointer should
-; not be moved over stores to stack memory.
+; This is to explain that changes to the stack pointer should
+; not be moved over loads from or stores to stack memory.
(define_insn "stack_tie"
- [(set (match_operand:BLK 0 "memory_operand" "+m")
- (unspec:BLK [(match_dup 0)] UNSPEC_TIE))]
+ [(set (match_operand:BLK 0 "tie_operand" "")
+ (const_int 0))]
""
""
[(set_attr "length" "0")])
-; Like stack_tie, but depend on both fp and sp based memory.
-(define_insn "frame_tie"
- [(set (match_operand:BLK 0 "memory_operand" "+m")
- (unspec:BLK [(match_dup 0)
- (match_operand:BLK 1 "memory_operand" "m")] UNSPEC_TIE))]
- ""
- ""
- [(set_attr "length" "0")])
-
-
(define_expand "epilogue"
[(use (const_int 0))]
""
--
Alan Modra
Australia Development Lab, IBM
