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* explow.c (anti_adjust_stack_and_probe_stack_clash): Avoid probing
the red zone for stack_clash_protection_final_dynamic_probe targets
when the total dynamic stack size is zero bytes.
diff -Nrup a/gcc/explow.c b/gcc/explow.c
--- a/gcc/explow.c 2017-11-14 23:33:15.403557607 -0700
+++ b/gcc/explow.c 2017-11-14 23:33:56.243239120 -0700
@@ -1934,6 +1934,13 @@ anti_adjust_stack_and_probe_stack_clash
if (size != CONST0_RTX (Pmode)
&& targetm.stack_clash_protection_final_dynamic_probe (residual))
{
+ /* SIZE could be zero at runtime and in that case *sp could hold
+ live data. Furthermore, we don't want to probe into the red
+ zone.
+
+ Go ahead and just guard a probe at *sp on SIZE != 0 at runtime
+ if SIZE is not a compile time constant. */
+
/* Ideally we would just probe at *sp. However, if SIZE is not
a compile-time constant, but is zero at runtime, then *sp
might hold live data. So probe at *sp if we know that
@@ -1946,9 +1953,12 @@ anti_adjust_stack_and_probe_stack_clash
}
else
{
- emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
- -GET_MODE_SIZE (word_mode)));
+ rtx label = gen_label_rtx ();
+ emit_cmp_and_jump_insns (size, CONST0_RTX (GET_MODE (size)),
+ EQ, NULL_RTX, Pmode, 1, label);
+ emit_stack_probe (stack_pointer_rtx);
emit_insn (gen_blockage ());
+ emit_label (label);
}
}
}
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