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rs6000: Don't touch below the stack pointer (PR77687) 

With the 32-bit SVR4 ABI we don't have a red zone, so we have to restore
the callee-saved registers before we restore the stack pointer.

The previous fix for this PR failed in two ways, for huge frames: first,
we use a negative offset from r11 in that case, so the (mem:BLK 11) access
does no good; second, sched does not handle accesses to mem:BLK correctly
in this case (does not make dependencies).

This patch fixes it by doing a store to (mem:BLK (scratch)) instead.
This means no unrelated (not to stack) loads/stores can be moved over the
stack restore either, but so be it.


	PR target/77687
	* config/rs6000/rs6000.md (stack_restore_tie): Store to a scratch
	address instead of to r1 and r11.

gcc/testsuite/
	PR target/77687
	* gcc.target/powerpc/pr77687.c: New testcase.

From-SVN: r254968
This commit is contained in:
Segher Boessenkool 2017-11-20 21:10:28 +01:00 committed by Segher Boessenkool
parent 8ffd559cd5
commit 5c956beb8a
4 changed files with 39 additions and 4 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2017-11-20 Segher Boessenkool <segher@kernel.crashing.org>
Backport from mainline
2017-09-20 Segher Boessenkool <segher@kernel.crashing.org>
PR target/77687
* config/rs6000/rs6000.md (stack_restore_tie): Store to a scratch
address instead of to r1 and r11.
2017-11-17 Vineet Gupta <vgupta@synopsys.com>
* config.gcc: Remove uclibc from arc target spec.

6
gcc/config/rs6000/rs6000.md
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@ -13304,14 +13304,12 @@
; 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. This insn is an add or mr, and a stack_tie on the
; operands of that.
; one. See PR77687. This insn is an add or mr, and a memory clobber.
(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))]
(set (mem:BLK (scratch)) (const_int 0))]
"TARGET_32BIT"
"@
mr %0,%1

8
gcc/testsuite/ChangeLog
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@ -1,3 +1,11 @@
2017-11-20 Segher Boessenkool <segher@kernel.crashing.org>
Backport from mainline
2017-09-20 Segher Boessenkool <segher@kernel.crashing.org>
PR target/77687
* gcc.target/powerpc/pr77687.c: New testcase.
2017-11-15 Richard Biener <rguenther@suse.de>
PR tree-optimization/82985

20
gcc/testsuite/gcc.target/powerpc/pr77687.c Normal file
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@ -0,0 +1,20 @@
/* { dg-options "-std=gnu99 -O2" } */
/* { dg-final { scan-assembler-not {\mmr r?1,r?11\M.*11.*\mblr\M} } } */
/* PR77687: We used to do stack accesses (via r11) after restoring r1. */
void g(int, char *);
const char * dum = "hello";
void f(int x)
{
char big[200000];
start:
g(x, big);
g(x, big);
register void *p asm("r11") = &&start;
asm("" : : "r"(p));
asm("" : : :"r28");
asm("" : : :"r29");
asm("" : : :"r30");
}