Hi All,
This is a re-spin to address review comments. No code change aside from a
variable rename.
Ok for trunk?
Thanks,
Tamar
gcc/
2018-08-07 Tamar Christina <tamar.christ...@arm.com>
PR target/86486
* config/aarch64/aarch64.h (STACK_CLASH_MIN_BYTES_OUTGOING_ARGS,
STACK_DYNAMIC_OFFSET): New.
* config/aarch64/aarch64.c (aarch64_layout_frame):
Update outgoing args size.
(aarch64_stack_clash_protection_alloca_probe_range,
TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE): New.
gcc/testsuite/
2018-08-07 Tamar Christina <tamar.christ...@arm.com>
PR target/86486
* gcc.target/aarch64/stack-check-alloca-1.c: New.
* gcc.target/aarch64/stack-check-alloca-10.c: New.
* gcc.target/aarch64/stack-check-alloca-2.c: New.
* gcc.target/aarch64/stack-check-alloca-3.c: New.
* gcc.target/aarch64/stack-check-alloca-4.c: New.
* gcc.target/aarch64/stack-check-alloca-5.c: New.
* gcc.target/aarch64/stack-check-alloca-6.c: New.
* gcc.target/aarch64/stack-check-alloca-7.c: New.
* gcc.target/aarch64/stack-check-alloca-8.c: New.
* gcc.target/aarch64/stack-check-alloca-9.c: New.
* gcc.target/aarch64/stack-check-alloca.h: New.
* gcc.target/aarch64/stack-check-14.c: New.
* gcc.target/aarch64/stack-check-15.c: New.
> -----Original Message-----
> From: Jeff Law <l...@redhat.com>
> Sent: Friday, August 3, 2018 19:05
> To: Tamar Christina <tamar.christ...@arm.com>; gcc-patches@gcc.gnu.org
> Cc: nd <n...@arm.com>; James Greenhalgh <james.greenha...@arm.com>;
> Richard Earnshaw <richard.earns...@arm.com>; Marcus Shawcroft
> <marcus.shawcr...@arm.com>
> Subject: Re: [PATCH][GCC][AArch64] Ensure that outgoing argument size is at
> least 8 bytes when alloca and stack-clash. [Patch (3/6)]
>
> On 07/25/2018 05:09 AM, Tamar Christina wrote:
> > Hi All,
> >
> > Attached an updated patch which documents what the test cases are
> expecting as requested.
> >
> > Ok for trunk?
> >
> > Thanks,
> > Tamar
> >
> > gcc/
> > 2018-07-25 Tamar Christina <tamar.christ...@arm.com>
> >
> > PR target/86486
> > * config/aarch64/aarch64.h (STACK_CLASH_OUTGOING_ARGS,
> > STACK_DYNAMIC_OFFSET): New.
> > * config/aarch64/aarch64.c (aarch64_layout_frame):
> > Update outgoing args size.
> > (aarch64_stack_clash_protection_alloca_probe_range,
> > TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE):
> New.
> >
> > gcc/testsuite/
> > 2018-07-25 Tamar Christina <tamar.christ...@arm.com>
> >
> > PR target/86486
> > * gcc.target/aarch64/stack-check-alloca-1.c: New.
> > * gcc.target/aarch64/stack-check-alloca-10.c: New.
> > * gcc.target/aarch64/stack-check-alloca-2.c: New.
> > * gcc.target/aarch64/stack-check-alloca-3.c: New.
> > * gcc.target/aarch64/stack-check-alloca-4.c: New.
> > * gcc.target/aarch64/stack-check-alloca-5.c: New.
> > * gcc.target/aarch64/stack-check-alloca-6.c: New.
> > * gcc.target/aarch64/stack-check-alloca-7.c: New.
> > * gcc.target/aarch64/stack-check-alloca-8.c: New.
> > * gcc.target/aarch64/stack-check-alloca-9.c: New.
> > * gcc.target/aarch64/stack-check-alloca.h: New.
> > * gcc.target/aarch64/stack-check-14.c: New.
> > * gcc.target/aarch64/stack-check-15.c: New.
> >
> >> -----Original Message-----
> >> From: Tamar Christina
> >> Sent: Friday, July 13, 2018 17:36
> >> To: Tamar Christina <tamar.christ...@arm.com>;
> >> gcc-patches@gcc.gnu.org
> >> Cc: nd <n...@arm.com>; James Greenhalgh
> <james.greenha...@arm.com>;
> >> Richard Earnshaw <richard.earns...@arm.com>; Marcus Shawcroft
> >> <marcus.shawcr...@arm.com>
> >> Subject: RE: [PATCH][GCC][AArch64] Ensure that outgoing argument size
> >> is at least 8 bytes when alloca and stack-clash. [Patch (3/6)]
> >>
> >> Hi All,
> >>
> >> I'm sending an updated patch which updates a testcase that hits one
> >> of our corner cases.
> >> This is an assembler scan only update in a testcase.
> >>
> >> Regards,
> >> Tamar
> >>
> >>> -----Original Message-----
> >>> From: Tamar Christina <tamar.christ...@arm.com>
> >>> Sent: Wednesday, July 11, 2018 12:21
> >>> To: gcc-patches@gcc.gnu.org
> >>> Cc: nd <n...@arm.com>; James Greenhalgh
> <james.greenha...@arm.com>;
> >>> Richard Earnshaw <richard.earns...@arm.com>; Marcus Shawcroft
> >>> <marcus.shawcr...@arm.com>
> >>> Subject: [PATCH][GCC][AArch64] Ensure that outgoing argument size is
> >>> at least 8 bytes when alloca and stack-clash. [Patch (3/6)]
> >>>
> >>> Hi All,
> >>>
> >>> This patch adds a requirement that the number of outgoing arguments
> >>> for a function is at least 8 bytes when using stack-clash protection.
> >>>
> >>> By using this condition we can avoid a check in the alloca code and
> >>> so have smaller and simpler code there.
> >>>
> >>> A simplified version of the AArch64 stack frames is:
> >>>
> >>> +-----------------------+
> >>> | |
> >>> | |
> >>> | |
> >>> +-----------------------+
> >>> |LR |
> >>> +-----------------------+
> >>> |FP |
> >>> +-----------------------+
> >>> |dynamic allocations | ---- expanding area which will push the
> outgoing
> >>> +-----------------------+ args down during each allocation.
> >>> |padding |
> >>> +-----------------------+
> >>> |outgoing stack args | ---- safety buffer of 8 bytes (aligned)
> >>> +-----------------------+
> >>>
> >>> By always defining an outgoing argument, alloca(0) effectively is
> >>> safe to probe at $sp due to the reserved buffer being there. It
> >>> will never corrupt the stack.
> >>>
> >>> This is also safe for alloca(x) where x is 0 or x % page_size == 0.
> >>> In the former it is the same case as alloca(0) while the latter is
> >>> safe because any allocation pushes the outgoing stack args down:
> >>>
> >>> |FP |
> >>> +-----------------------+
> >>> | |
> >>> |dynamic allocations | ---- alloca (x)
> >>> | |
> >>> +-----------------------+
> >>> |padding |
> >>> +-----------------------+
> >>> |outgoing stack args | ---- safety buffer of 8 bytes (aligned)
> >>> +-----------------------+
> >>>
> >>> Which means when you probe for the residual, if it's 0 you'll again
> >>> just probe in the outgoing stack args range, which we know is
> >>> non-zero (at
> >> least 8 bytes).
> >>>
> >>> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> >>> Target was tested with stack clash on and off by default.
> >>>
> >>> Ok for trunk?
> >>>
> >>> Thanks,
> >>> Tamar
> >>>
> >>> gcc/
> >>> 2018-07-11 Tamar Christina <tamar.christ...@arm.com>
> >>>
> >>> PR target/86486
> >>> * config/aarch64/aarch64.h (STACK_CLASH_OUTGOING_ARGS,
> >>> STACK_DYNAMIC_OFFSET): New.
> >>> * config/aarch64/aarch64.c (aarch64_layout_frame):
> >>> Update outgoing args size.
> >>> (aarch64_stack_clash_protection_alloca_probe_range,
> >>> TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE):
> >>> New.
> >>>
> >>> gcc/testsuite/
> >>> 2018-07-11 Tamar Christina <tamar.christ...@arm.com>
> >>>
> >>> PR target/86486
> >>> * gcc.target/aarch64/stack-check-alloca-1.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-10.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-2.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-3.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-4.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-5.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-6.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-7.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-8.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca-9.c: New.
> >>> * gcc.target/aarch64/stack-check-alloca.h: New.
> >>> * gcc.target/aarch64/stack-check-14.c: New.
> >>> * gcc.target/aarch64/stack-check-15.c: New.
> >>>
> >>> --
> Likewise -- no concerns on my end. AArch64 maintainers have the final say.
>
> jeff
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 1345f0eb171d05e2b833935c0a32f79c3db03f99..9a51700fa38f2ddd8e003adf209755bcfafa9ee0 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -88,6 +88,10 @@
before probing has to be done for stack clash protection. */
#define STACK_CLASH_CALLER_GUARD 1024
+/* This value represents the minimum amount of bytes we expect the function's
+ outgoing arguments to be when stack-clash is enabled. */
+#define STACK_CLASH_MIN_BYTES_OUTGOING_ARGS 8
+
/* This value controls how many pages we manually unroll the loop for when
generating stack clash probes. */
#define STACK_CLASH_MAX_UNROLL_PAGES 4
@@ -1069,4 +1073,17 @@ extern poly_uint16 aarch64_sve_vg;
#define REGMODE_NATURAL_SIZE(MODE) aarch64_regmode_natural_size (MODE)
+/* Allocate a minimum of STACK_CLASH_MIN_BYTES_OUTGOING_ARGS bytes for the
+ outgoing arguments if stack clash protection is enabled. This is essential
+ as the extra arg space allows us to skip a check in alloca. */
+#undef STACK_DYNAMIC_OFFSET
+#define STACK_DYNAMIC_OFFSET(FUNDECL) \
+ ((flag_stack_clash_protection \
+ && cfun->calls_alloca \
+ && known_lt (crtl->outgoing_args_size, \
+ STACK_CLASH_MIN_BYTES_OUTGOING_ARGS)) \
+ ? ROUND_UP (STACK_CLASH_MIN_BYTES_OUTGOING_ARGS, \
+ STACK_BOUNDARY / BITS_PER_UNIT) \
+ : (crtl->outgoing_args_size + STACK_POINTER_OFFSET))
+
#endif /* GCC_AARCH64_H */
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 19f67112454aeb32ae0905e3511f03dfd803b87f..105750d1c2cba470d14d8079aa61195d4e03978c 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -4047,6 +4047,10 @@ aarch64_layout_frame (void)
cfun->machine->frame.emit_frame_chain = aarch64_needs_frame_chain ();
+ /* Adjust the outgoing arguments size if required. Keep it in sync with what
+ the mid-end is doing. */
+ crtl->outgoing_args_size = STACK_DYNAMIC_OFFSET (cfun);
+
#define SLOT_NOT_REQUIRED (-2)
#define SLOT_REQUIRED (-1)
@@ -4814,6 +4818,16 @@ aarch64_set_handled_components (sbitmap components)
cfun->machine->reg_is_wrapped_separately[regno] = true;
}
+/* On AArch64 we have an ABI defined safe buffer. This constant is used to
+ determining the probe offset for alloca. */
+
+static HOST_WIDE_INT
+aarch64_stack_clash_protection_alloca_probe_range (void)
+{
+ return STACK_CLASH_CALLER_GUARD;
+}
+
+
/* Allocate POLY_SIZE bytes of stack space using TEMP1 and TEMP2 as scratch
registers. If POLY_SIZE is not large enough to require a probe this function
will only adjust the stack. When allocating the stack space
@@ -18382,6 +18396,10 @@ aarch64_libgcc_floating_mode_supported_p
#undef TARGET_CONSTANT_ALIGNMENT
#define TARGET_CONSTANT_ALIGNMENT aarch64_constant_alignment
+#undef TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE
+#define TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE \
+ aarch64_stack_clash_protection_alloca_probe_range
+
#undef TARGET_COMPUTE_PRESSURE_CLASSES
#define TARGET_COMPUTE_PRESSURE_CLASSES aarch64_compute_pressure_classes
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-14.c b/gcc/testsuite/gcc.target/aarch64/stack-check-14.c
new file mode 100644
index 0000000000000000000000000000000000000000..a573d108a0ce0243e038411aa01eb65dfd81a460
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-14.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+int t1(int);
+
+int t2(int x)
+{
+ char *p = __builtin_alloca (4050);
+ x = t1 (x);
+ return p[x];
+}
+
+
+/* This test has a constant sized alloca that is smaller than the
+ probe interval. Only one probe is required since the value is larger
+ than 1024 bytes but smaller than 63k.
+
+ The form can change quite a bit so we just check for two
+ probes without looking at the actual address. */
+/* { dg-final { scan-assembler-times "str\\txzr," 1 } } */
+
+
+
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-15.c b/gcc/testsuite/gcc.target/aarch64/stack-check-15.c
new file mode 100644
index 0000000000000000000000000000000000000000..497d83e6596a3cbfce898ca6cda1a65d5fe76d0b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-15.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+int t1(int);
+
+int t2(int x)
+{
+ char *p = __builtin_alloca (x);
+ x = t1 (x);
+ return p[x];
+}
+
+
+/* This test has a variable sized alloca. It requires 3 probes.
+ One in the loop, one for the residual, one for when it's < 1024 and one for
+ when it's not.
+
+ The form can change quite a bit so we just check for two
+ probes without looking at the actual address. */
+/* { dg-final { scan-assembler-times "str\\txzr," 3 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-1.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..7fc189f6210d97fe87af489f11c94a7a98c9ac94
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE y
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 2 } } */
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp\]} 1 } } */
+
+/* Dynamic alloca, expect loop, and 2 probes with 1kB offset and 1 at sp.
+ 1st probe is inside the loop for the full guard-size allocations, second
+ probe is for the case where residual is zero and the final probe for when
+ residiual is > 1024 bytes. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-10.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-10.c
new file mode 100644
index 0000000000000000000000000000000000000000..7c42206d3158d624815a5cc13b2e619c4a432dda
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-10.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 127.5 * 64 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 2 } } */
+
+/* Large alloca of an amount which isn't a multiple of a guard-size, and
+ residiual is more than 1kB. Loop expected with one 1Kb probe offset and
+ one residual probe at offset 1kB. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-2.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..69fdd16e35a296276acaf76bb0e0954ffba5a421
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-2.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 0
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-not {str\s+xzr,} } } */
+
+/* Alloca of 0 should emit no probes, boundary condition. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-3.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..fba3a7a25b726558d4167f3d71c9490d1c89225d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-3.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 100
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 8\]} 1 } } */
+
+/* Alloca is less than 1kB, 1 probe expected at word offset. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-4.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..d53f30a4133b7b2af74823d87ce88ff0d2116550
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-4.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 2 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+
+/* Alloca is more than 1kB, but less than guard-size, 1 probe expected at
+ 1kB offset. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-5.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..e0ff99ffbe1504d28aff314eeefdcac027321c5d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-5.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 63 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+
+/* Alloca is more than 1kB, but less than guard-size, 1 probe expected at
+ 1kB offset. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-6.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..c4bad9a2f46b405a7f01a71733f4534c66515742
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-6.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 63.5 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+
+/* Alloca is more than 1kB, but less than guard-size, 1 probe expected at 1kB
+ offset. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-7.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-7.c
new file mode 100644
index 0000000000000000000000000000000000000000..cba9ff89c1a41da1f6b439239114b25351cab1d0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-7.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 64 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+
+/* Alloca is exactly one guard-size, 1 probe expected at 1kB offset.
+ Boundary condition. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-8.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-8.c
new file mode 100644
index 0000000000000000000000000000000000000000..5a35411b34483231bd05859b963a031d0011ad2b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-8.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 65 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 8\]} 1 } } */
+
+/* Alloca is more than one guard-page, and residual is exactly 1Kb. 2 probes
+ expected. One at 1kB offset for the guard-size allocation and one at word
+ offset for the residual. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-9.c b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-9.c
new file mode 100644
index 0000000000000000000000000000000000000000..5773d8052bc2d89842ad591b12807056a0247ac5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca-9.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-clash-protection --param stack-clash-protection-guard-size=16" } */
+/* { dg-require-effective-target supports_stack_clash_protection } */
+
+#define SIZE 127 * 64 * 1024
+#include "stack-check-alloca.h"
+
+/* { dg-final { scan-assembler-times {str\s+xzr, \[sp, 1024\]} 1 } } */
+
+/* Large alloca of a constant amount which is a multiple of a guard-size,
+ no residiual. Loop expected with one 1Kb probe offset and no residual probe
+ because residual is at compile time known to be zero. */
diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-alloca.h b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca.h
new file mode 100644
index 0000000000000000000000000000000000000000..a4f7fa2dd351cc7b76784103fc645a066c5ba6e3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-alloca.h
@@ -0,0 +1,13 @@
+#include <alloca.h>
+
+__attribute__((noinline, noipa))
+void g (char* ptr, int y)
+{
+ ptr[y] = '\0';
+}
+
+void f_caller (int y)
+{
+ char* pStr = alloca(SIZE);
+ g (pStr, y);
+}
\ No newline at end of file
