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5ed81e |
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* explow.c (anti_adjust_stack_and_probe_stack_clash): Avoid probing
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the red zone for stack_clash_protection_final_dynamic_probe targets
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when the total dynamic stack size is zero bytes.
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diff -Nrup a/gcc/explow.c b/gcc/explow.c
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--- a/gcc/explow.c 2017-11-14 23:33:15.403557607 -0700
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+++ b/gcc/explow.c 2017-11-14 23:33:56.243239120 -0700
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@@ -1934,6 +1934,13 @@ anti_adjust_stack_and_probe_stack_clash
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if (size != CONST0_RTX (Pmode)
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&& targetm.stack_clash_protection_final_dynamic_probe (residual))
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{
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+ /* SIZE could be zero at runtime and in that case *sp could hold
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+ live data. Furthermore, we don't want to probe into the red
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+ zone.
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+
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+ Go ahead and just guard a probe at *sp on SIZE != 0 at runtime
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+ if SIZE is not a compile time constant. */
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+
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/* Ideally we would just probe at *sp. However, if SIZE is not
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a compile-time constant, but is zero at runtime, then *sp
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might hold live data. So probe at *sp if we know that
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@@ -1946,9 +1953,12 @@ anti_adjust_stack_and_probe_stack_clash
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}
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else
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{
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- emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
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- -GET_MODE_SIZE (word_mode)));
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+ rtx label = gen_label_rtx ();
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+ emit_cmp_and_jump_insns (size, CONST0_RTX (GET_MODE (size)),
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+ EQ, NULL_RTX, Pmode, 1, label);
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+ emit_stack_probe (stack_pointer_rtx);
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emit_insn (gen_blockage ());
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+ emit_label (label);
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}
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}
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}
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