The x86 backend defines a PROBE_INTERVAL which is supposed to be used by
the -fstack-check= mechanisms.
Some stack-clash code was using PROBE_INTERVAL rather than querying the
PARAM system for the right value. If the former is larger than the
latter and we allocate a large stack, then the loop to probe the stack
space may not terminate (PR82788)
Rather than playing wack-a-mole on this problem I decided to just create
a little helper that would return the right probing interval for
whatever option was active, then changed all the x86 code to use that
new function. The patch is mostly a search/replace and looks much
bigger than it really is.
Bootstrapped and regression tested on x86_64. OK for the trunk?
Jeff
commit 2939aa3d6f49bd2b4376f23ebbff4bea4c9afa12
Author: Jeff Law <l...@tor.usersys.redhat.com>
Date: Thu Nov 2 20:15:11 2017 -0400
FIx bz
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fc43962..672a085 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -12083,7 +12083,17 @@ release_scratch_register_on_entry (struct scratch_reg
*sr)
}
}
-#define PROBE_INTERVAL (1 << STACK_CHECK_PROBE_INTERVAL_EXP)
+/* Return the probing interval for -fstack-clash-protection. */
+
+static HOST_WIDE_INT
+get_probe_interval (void)
+{
+ if (flag_stack_clash_protection)
+ return (HOST_WIDE_INT_1U
+ << PARAM_VALUE (PARAM_STACK_CLASH_PROTECTION_PROBE_INTERVAL));
+ else
+ return (HOST_WIDE_INT_1U << STACK_CHECK_PROBE_INTERVAL_EXP);
+}
/* Emit code to adjust the stack pointer by SIZE bytes while probing it.
@@ -12147,8 +12157,7 @@ ix86_adjust_stack_and_probe_stack_clash (const
HOST_WIDE_INT size)
/* We're allocating a large enough stack frame that we need to
emit probes. Either emit them inline or in a loop depending
on the size. */
- HOST_WIDE_INT probe_interval
- = 1 << PARAM_VALUE (PARAM_STACK_CLASH_PROTECTION_PROBE_INTERVAL);
+ HOST_WIDE_INT probe_interval = get_probe_interval ();
if (size <= 4 * probe_interval)
{
HOST_WIDE_INT i;
@@ -12157,7 +12166,7 @@ ix86_adjust_stack_and_probe_stack_clash (const
HOST_WIDE_INT size)
/* Allocate PROBE_INTERVAL bytes. */
rtx insn
= pro_epilogue_adjust_stack (stack_pointer_rtx, stack_pointer_rtx,
- GEN_INT (-PROBE_INTERVAL), -1,
+ GEN_INT (-probe_interval), -1,
m->fs.cfa_reg == stack_pointer_rtx);
add_reg_note (insn, REG_STACK_CHECK, const0_rtx);
@@ -12250,7 +12259,7 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
that's the easy case. The run-time loop is made up of 9 insns in the
generic case while the compile-time loop is made up of 3+2*(n-1) insns
for n # of intervals. */
- if (size <= 4 * PROBE_INTERVAL)
+ if (size <= 4 * get_probe_interval ())
{
HOST_WIDE_INT i, adjust;
bool first_probe = true;
@@ -12259,15 +12268,15 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
values of N from 1 until it exceeds SIZE. If only one probe is
needed, this will not generate any code. Then adjust and probe
to PROBE_INTERVAL + SIZE. */
- for (i = PROBE_INTERVAL; i < size; i += PROBE_INTERVAL)
+ for (i = get_probe_interval (); i < size; i += get_probe_interval ())
{
if (first_probe)
{
- adjust = 2 * PROBE_INTERVAL + dope;
+ adjust = 2 * get_probe_interval () + dope;
first_probe = false;
}
else
- adjust = PROBE_INTERVAL;
+ adjust = get_probe_interval ();
emit_insn (gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
@@ -12276,9 +12285,9 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
}
if (first_probe)
- adjust = size + PROBE_INTERVAL + dope;
+ adjust = size + get_probe_interval () + dope;
else
- adjust = size + PROBE_INTERVAL - i;
+ adjust = size + get_probe_interval () - i;
emit_insn (gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
@@ -12288,7 +12297,8 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
/* Adjust back to account for the additional first interval. */
last = emit_insn (gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
- PROBE_INTERVAL + dope)));
+ (get_probe_interval ()
+ + dope))));
}
/* Otherwise, do the same as above, but in a loop. Note that we must be
@@ -12306,7 +12316,7 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
/* Step 1: round SIZE to the previous multiple of the interval. */
- rounded_size = ROUND_DOWN (size, PROBE_INTERVAL);
+ rounded_size = ROUND_DOWN (size, get_probe_interval ());
/* Step 2: compute initial and final value of the loop counter. */
@@ -12314,7 +12324,7 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
/* SP = SP_0 + PROBE_INTERVAL. */
emit_insn (gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
- - (PROBE_INTERVAL + dope))));
+ - (get_probe_interval ()+ dope))));
/* LAST_ADDR = SP_0 + PROBE_INTERVAL + ROUNDED_SIZE. */
if (rounded_size <= (HOST_WIDE_INT_1 << 31))
@@ -12359,7 +12369,8 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
/* Adjust back to account for the additional first interval. */
last = emit_insn (gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
- PROBE_INTERVAL + dope)));
+ (get_probe_interval ()
+ + dope))));
release_scratch_register_on_entry (&sr);
}
@@ -12376,7 +12387,7 @@ ix86_adjust_stack_and_probe (const HOST_WIDE_INT size)
XVECEXP (expr, 0, 1)
= gen_rtx_SET (stack_pointer_rtx,
plus_constant (Pmode, stack_pointer_rtx,
- PROBE_INTERVAL + dope + size));
+ get_probe_interval () + dope + size));
add_reg_note (last, REG_FRAME_RELATED_EXPR, expr);
RTX_FRAME_RELATED_P (last) = 1;
@@ -12403,7 +12414,7 @@ output_adjust_stack_and_probe (rtx reg)
/* SP = SP + PROBE_INTERVAL. */
xops[0] = stack_pointer_rtx;
- xops[1] = GEN_INT (PROBE_INTERVAL);
+ xops[1] = GEN_INT (get_probe_interval ());
output_asm_insn ("sub%z0\t{%1, %0|%0, %1}", xops);
/* Probe at SP. */
@@ -12433,14 +12444,14 @@ ix86_emit_probe_stack_range (HOST_WIDE_INT first,
HOST_WIDE_INT size)
that's the easy case. The run-time loop is made up of 6 insns in the
generic case while the compile-time loop is made up of n insns for n #
of intervals. */
- if (size <= 6 * PROBE_INTERVAL)
+ if (size <= 6 * get_probe_interval ())
{
HOST_WIDE_INT i;
/* Probe at FIRST + N * PROBE_INTERVAL for values of N from 1 until
it exceeds SIZE. If only one probe is needed, this will not
generate any code. Then probe at FIRST + SIZE. */
- for (i = PROBE_INTERVAL; i < size; i += PROBE_INTERVAL)
+ for (i = get_probe_interval (); i < size; i += get_probe_interval ())
emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
-(first + i)));
@@ -12463,7 +12474,7 @@ ix86_emit_probe_stack_range (HOST_WIDE_INT first,
HOST_WIDE_INT size)
/* Step 1: round SIZE to the previous multiple of the interval. */
- rounded_size = ROUND_DOWN (size, PROBE_INTERVAL);
+ rounded_size = ROUND_DOWN (size, get_probe_interval ());
/* Step 2: compute initial and final value of the loop counter. */
@@ -12524,7 +12535,7 @@ output_probe_stack_range (rtx reg, rtx end)
/* TEST_ADDR = TEST_ADDR + PROBE_INTERVAL. */
xops[0] = reg;
- xops[1] = GEN_INT (PROBE_INTERVAL);
+ xops[1] = GEN_INT (get_probe_interval ());
output_asm_insn ("sub%z0\t{%1, %0|%0, %1}", xops);
/* Probe at TEST_ADDR. */
@@ -13182,7 +13193,7 @@ ix86_expand_prologue (void)
else if (STACK_CHECK_MOVING_SP)
{
if (!(crtl->is_leaf && !cfun->calls_alloca
- && allocate <= PROBE_INTERVAL))
+ && allocate <= get_probe_interval ()))
{
ix86_adjust_stack_and_probe (allocate);
allocate = 0;
@@ -13199,7 +13210,7 @@ ix86_expand_prologue (void)
{
if (crtl->is_leaf && !cfun->calls_alloca)
{
- if (size > PROBE_INTERVAL)
+ if (size > get_probe_interval ())
ix86_emit_probe_stack_range (0, size);
}
else
@@ -13210,7 +13221,7 @@ ix86_expand_prologue (void)
{
if (crtl->is_leaf && !cfun->calls_alloca)
{
- if (size > PROBE_INTERVAL
+ if (size > get_probe_interval ()
&& size > get_stack_check_protect ())
ix86_emit_probe_stack_range (get_stack_check_protect (),
size - get_stack_check_protect
());
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ea0c0e0..f0eda16 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,6 +1,8 @@
2017-11-02 Jeff Law <l...@redhat.com>
- * gcc.target/i386/stack-check-12.c: New test
+ * gcc.c-torture/execute/pr82788.c: New test.
+
+ * gcc.target/i386/stack-check-12.c: New test.
2017-11-02 Nathan Sidwell <nat...@acm.org>
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr82788.c
b/gcc/testsuite/gcc.c-torture/execute/pr82788.c
new file mode 100644
index 0000000..ceaa25f
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr82788.c
@@ -0,0 +1,2 @@
+
+int main() { int a[1442]; return 0;}
