> Am 11.01.2025 um 09:49 schrieb Andrew Pinski <quic_apin...@quicinc.com>:
>
> In this case, early phiopt would get rid of the user provided predicator
> for hot/cold as it would remove the basic blocks. The easiest and best option
> is
> for early phi-opt don't do phi-opt if the middle basic-block(s) have either
> a hot or cold predict statement. Then after inlining, jump threading will
> most likely
> happen and that will keep around the predictor.
>
> Note this only needs to be done for match_simplify_replacement and not the
> other
> phi-opt functions because currently only match_simplify_replacement is able
> to skip
> middle bb with predicator statements in it.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.
Hmm, I think we still want to allow abs/min/max replacements early I think.
What kind of replacement is performed in the problematic case?
>
> PR tree-optimization/117935
>
> gcc/ChangeLog:
>
> * tree-ssa-phiopt.cc (contains_hot_cold_predict): New function.
> (match_simplify_replacement): Return early if early_p and one of
> the middle bb(s) have a hot/cold predict statement.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/predict-24.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/testsuite/gcc.dg/predict-24.c | 24 +++++++++++++++++++++
> gcc/tree-ssa-phiopt.cc | 35 +++++++++++++++++++++++++++++++
> 2 files changed, 59 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/predict-24.c
>
> diff --git a/gcc/testsuite/gcc.dg/predict-24.c
> b/gcc/testsuite/gcc.dg/predict-24.c
> new file mode 100644
> index 00000000000..b2c8a77c323
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/predict-24.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
> +/* PR tree-optimization/117935 */
> +
> +static inline bool has_value(bool b)
> +{
> + if (b)
> + {
> + [[gnu::hot, gnu::unused]] label1:
> + return true;
> + }
> + else
> + return false;
> +}
> +/* The hot label should last until it gets inlined into value_or and
> jump_threaded. */
> +int value_or(bool b, int def0, int def1)
> +{
> + if (has_value(b))
> + return def0;
> + else
> + return def1;
> +}
> +/* { dg-final { scan-tree-dump-times "first match heuristics: 90.00%" 2
> "profile_estimate"} } */
> +/* { dg-final { scan-tree-dump-times "hot label heuristics of edge
> \[0-9\]+->\[0-9]+: 90.00%" 2 "profile_estimate"} } */
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index 64d3ba9e160..8fed3eadbb0 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -56,6 +56,7 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-ssa-dce.h"
> #include "calls.h"
> #include "tree-ssa-loop-niter.h"
> +#include "gimple-predict.h"
>
> /* Return the singleton PHI in the SEQ of PHIs for edges E0 and E1. */
>
> @@ -916,6 +917,27 @@ auto_flow_sensitive::~auto_flow_sensitive ()
> p.second.restore (p.first);
> }
>
> +/* Returns true if BB contains an user provided predictor
> + (PRED_HOT_LABEL/PRED_COLD_LABEL). */
> +
> +static bool
> +contains_hot_cold_predict (basic_block bb)
> +{
> + gimple_stmt_iterator gsi;
> + gsi = gsi_start_nondebug_after_labels_bb (bb);
> + for (; !gsi_end_p (gsi); gsi_next_nondebug (&gsi))
> + {
> + gimple *s = gsi_stmt (gsi);
> + if (gimple_code (s) != GIMPLE_PREDICT)
> + continue;
> + auto predict = gimple_predict_predictor (s);
> + if (predict == PRED_HOT_LABEL
> + || predict == PRED_COLD_LABEL)
> + return true;
> + }
> + return false;
> +}
> +
> /* The function match_simplify_replacement does the main work of doing the
> replacement using match and simplify. Return true if the replacement is
> done.
> Otherwise return false.
> @@ -953,6 +975,19 @@ match_simplify_replacement (basic_block cond_bb,
> basic_block middle_bb,
> stmt_to_move_alt))
> return false;
>
> + /* For early phiopt, we don't want to lose user generated predictors,
> + that is if either middle bb contains either a hot or cold label predict,
> + the phiopt should be skipped. */
> + if (early_p)
> + {
> + if (contains_hot_cold_predict (middle_bb))
> + return false;
> + if (threeway_p
> + && middle_bb != middle_bb_alt
> + && contains_hot_cold_predict (middle_bb_alt))
> + return false;
> + }
> +
> /* Do not make conditional undefs unconditional. */
> if ((TREE_CODE (arg0) == SSA_NAME
> && ssa_name_maybe_undef_p (arg0))
> --
> 2.43.0
>
