explow.c (anti_adjust_stack_and_probe_stack_clash): Avoid probing the red zone for...

	* 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.

From-SVN: r254753

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c404eb8e5a7de82abdc5386fa7affc5f2c2dcd3e..08642663d953ea622a7e13b8304ec806650c6475 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2017-11-14  Jeff Law  <law@redhat.com>
 
+       * 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.
+
        * tree-ssa-threadupdate.c (thread_through_all_blocks): Thread
        blocks is post order.
 

diff --git a/gcc/explow.c b/gcc/explow.c
index 662865d2808beceafd28ce72def65c5964037a0b..96334b2b448835791ed95352c6e4af32edd0670c 100644 (file)
--- a/gcc/explow.c
+++ b/gcc/explow.c
@@ -1999,6 +1999,13 @@ anti_adjust_stack_and_probe_stack_clash (rtx size)
   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
@@ -2011,9 +2018,12 @@ anti_adjust_stack_and_probe_stack_clash (rtx size)
        }
       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);
        }
     }
 }