[PR105455] Set edge probabilities when hardening conditionals
When turning unconditional edges into conditional, as in
gimple-harden-conditionals.cc:insert_check_and_trap, the newly-created
edge's probability comes out uninitialized, while the previously
unconditional edge's probability is presumably
profile_probability::always.
Mixing initialized and uninitialized probabilities before expand
breaks predict.cc:force_edge_cold: the initialized probability may end
up copied to a REG_BR_PROB note in a conditional branch insn, but if
force_edge_cold is called on that edge, it will find another edge with
uninitialized probability and assume the note is absent. Later on,
rtl_verify_edges complains that the note does not match the
probability modified by force_edge_cold in the edge.
This patch sets probabilities for edges affected by hardening of
conditionals, both the newly-created edges to trap blocks and the
previously-unconditional edges, so that the former are considered
never taken, while the latter are confirmed as always taken.
for gcc/ChangeLog
PR rtl-optimization/105455
* gimple-harden-conditionals.cc (insert_check_and_trap): Set
probabilities for newly-conditional edges.
for gcc/testsuite/ChangeLog
PR rtl-optimization/105455
* gcc.dg/pr105455.c: New.
(cherry picked from commit 90a8eab4a1
)
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@ -254,8 +254,10 @@ insert_check_and_trap (location_t loc, gimple_stmt_iterator *gsip,
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equality. */
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single_succ_edge (chk)->flags &= ~EDGE_FALLTHRU;
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single_succ_edge (chk)->flags |= neg_true_false_flag;
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single_succ_edge (chk)->probability = profile_probability::always ();
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edge e = make_edge (chk, trp, true_false_flag);
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e->goto_locus = loc;
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e->probability = profile_probability::never ();
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if (dom_info_available_p (CDI_DOMINATORS))
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set_immediate_dominator (CDI_DOMINATORS, trp, chk);
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@ -0,0 +1,17 @@
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/* { dg-do compile } */
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/* { dg-options "-O1 -fharden-conditional-branches -funroll-loops --param max-loop-header-insns=1" } */
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__attribute__ ((cold)) void
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bar (void);
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void
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foo (int x)
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{
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if (x)
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{
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int i;
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for (i = 0; i < 101; ++i)
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bar ();
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}
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}
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