If we use ABI_V4 and we have a big stack frame, we end the epilogue
with a "mr 1,11" (or similar) instruction. This instruction however
has no dependencies on the earlier restores from stack (done via r11),
so sched2 can end up reordering the insns, which is bad because we
have no red zone so that you then restore from stack that is already
deallocated.
This fixes it by making that restore depend on the memory accesses.
Tested on powerpc64-linux {-m32,-m64}; is this okay for trunk? Do we
want a testcase for this?
Segher
2016-11-15 Segher Boessenkool <seg...@kernel.crashing.org>
* config/rs6000/rs6000.c (rs6000_emit_stack_reset): Emit the
stack_restore_tie insn instead of stack_tie, for the SVR4 and
SPE ABIs.
* config/rs6000/rs6000.md (stack_restore_tie): New define_insn.
---
gcc/config/rs6000/rs6000.c | 13 ++++++++-----
gcc/config/rs6000/rs6000.md | 16 ++++++++++++++++
2 files changed, 24 insertions(+), 5 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 8a04248..2ceddfd 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -27487,7 +27487,11 @@ rs6000_emit_stack_reset (rs6000_stack_t *info,
rtx frame_reg_rtx, HOST_WIDE_INT frame_off,
unsigned updt_regno)
{
- rtx updt_reg_rtx;
+ /* If there is nothing to do, don't do anything. */
+ if (frame_off == 0 && REGNO (frame_reg_rtx) == updt_regno)
+ return NULL_RTX;
+
+ rtx updt_reg_rtx = gen_rtx_REG (Pmode, updt_regno);
/* This blockage is needed so that sched doesn't decide to move
the sp change before the register restores. */
@@ -27495,18 +27499,17 @@ 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 (frame_reg_rtx, frame_pointer_needed);
+ return emit_insn (gen_stack_restore_tie (updt_reg_rtx, frame_reg_rtx,
+ GEN_INT (frame_off)));
/* If we are restoring registers out-of-line, we will be using the
"exit" variants of the restore routines, which will reset the
stack for us. But we do need to point updt_reg into the
right place for those routines. */
- updt_reg_rtx = gen_rtx_REG (Pmode, updt_regno);
-
if (frame_off != 0)
return emit_insn (gen_add3_insn (updt_reg_rtx,
frame_reg_rtx, GEN_INT (frame_off)));
- else if (REGNO (frame_reg_rtx) != updt_regno)
+ else
return emit_move_insn (updt_reg_rtx, frame_reg_rtx);
return NULL_RTX;
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index b3fe92a..a779f5c 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -12769,6 +12769,22 @@ (define_insn "stack_tie"
""
[(set_attr "length" "0")])
+; Some 32-bit ABIs do not have a red zone, so the stack deallocation has to
+; stay behind all restores from the stack, it cannot be reordered to before
+; one. See PR77687.
+(define_insn "stack_restore_tie"
+ [(set (match_operand:SI 0 "gpc_reg_operand" "=r,r")
+ (plus:SI (match_operand:SI 1 "gpc_reg_operand" "r,r")
+ (match_operand:SI 2 "reg_or_cint_operand" "O,rI")))
+ (set (mem:BLK (match_dup 0)) (const_int 0))
+ (set (mem:BLK (match_dup 1)) (const_int 0))]
+; (clobber (mem:BLK (scratch:SI)))]
+ "TARGET_32BIT"
+ "@
+ mr %0,%1
+ add%I2 %0,%1,%2"
+ [(set_attr "type" "*,add")])
+
(define_expand "epilogue"
[(use (const_int 0))]
""
--
1.9.3
