Hi,
as Juzhe noticed in gcc.dg/pr92301.c there was still something missing in
the last patch. The attached v2 makes sure we always have a COND_LEN operation
before returning true and initializes len and bias even if they are unused.
Bootstrapped and regtested on aarch64 and x86.
Regards
Robin
Subject: [PATCH v2] gimple-match: Do not try UNCOND optimization with
COND_LEN.
On riscv we mis-optimize conditional (length) operations into
unconditional operations e.g. in slp-reduc-7.c and
gcc.dg/pr92301.c.
This patch prevents optimizing e.g.
COND_LEN_ADD ({-1, ... }, a, 0, c, len, bias)
unconditionally into just "a".
Currently, we assume that COND_LEN operations can be optimized similarly
to COND operations. As the length is part of the mask (and usually not
compile-time constant), we must not perform any optimization that relies
on just the mask being "true". This patch ensures that we still have a
COND_LEN pattern after optimization.
gcc/ChangeLog:
PR target/111311
* gimple-match-exports.cc (maybe_resimplify_conditional_op):
Check for length masking.
(try_conditional_simplification): Check that the result is still
length masked.
---
gcc/gimple-match-exports.cc | 38 ++++++++++++++++++++++++++++++-------
gcc/gimple-match.h | 3 ++-
2 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/gcc/gimple-match-exports.cc b/gcc/gimple-match-exports.cc
index b36027b0bad..d41de98a3d3 100644
--- a/gcc/gimple-match-exports.cc
+++ b/gcc/gimple-match-exports.cc
@@ -262,7 +262,8 @@ maybe_resimplify_conditional_op (gimple_seq *seq,
gimple_match_op *res_op,
if (!res_op->cond.cond)
return false;
- if (!res_op->cond.else_value
+ if (!res_op->cond.len
+ && !res_op->cond.else_value
&& res_op->code.is_tree_code ())
{
/* The "else" value doesn't matter. If the "then" value is a
@@ -301,9 +302,12 @@ maybe_resimplify_conditional_op (gimple_seq *seq,
gimple_match_op *res_op,
/* If the "then" value is a gimple value and the "else" value matters,
create a VEC_COND_EXPR between them, then see if it can be further
- simplified. */
+ simplified.
+ Don't do this if we have a COND_LEN_ as that would make us lose the
+ length masking. */
gimple_match_op new_op;
- if (res_op->cond.else_value
+ if (!res_op->cond.len
+ && res_op->cond.else_value
&& VECTOR_TYPE_P (res_op->type)
&& gimple_simplified_result_is_gimple_val (res_op))
{
@@ -314,7 +318,7 @@ maybe_resimplify_conditional_op (gimple_seq *seq,
gimple_match_op *res_op,
return gimple_resimplify3 (seq, res_op, valueize);
}
- /* Otherwise try rewriting the operation as an IFN_COND_* call.
+ /* Otherwise try rewriting the operation as an IFN_COND_(LEN_)* call.
Again, this isn't a simplification in itself, since it's what
RES_OP already described. */
if (convert_conditional_op (res_op, &new_op))
@@ -386,9 +390,29 @@ try_conditional_simplification (internal_fn ifn,
gimple_match_op *res_op,
default:
gcc_unreachable ();
}
- *res_op = cond_op;
- maybe_resimplify_conditional_op (seq, res_op, valueize);
- return true;
+
+ if (len)
+ {
+ /* If we had a COND_LEN before we need to ensure that it stays that
+ way. */
+ gimple_match_op old_op = *res_op;
+ *res_op = cond_op;
+ maybe_resimplify_conditional_op (seq, res_op, valueize);
+
+ auto cfn = combined_fn (res_op->code);
+ if (internal_fn_p (cfn)
+ && internal_fn_len_index (as_internal_fn (cfn)) != -1)
+ return true;
+
+ *res_op = old_op;
+ return false;
+ }
+ else
+ {
+ *res_op = cond_op;
+ maybe_resimplify_conditional_op (seq, res_op, valueize);
+ return true;
+ }
}
/* Helper for the autogenerated code, valueize OP. */
diff --git a/gcc/gimple-match.h b/gcc/gimple-match.h
index bec3ff42e3e..d192b7dae3e 100644
--- a/gcc/gimple-match.h
+++ b/gcc/gimple-match.h
@@ -56,7 +56,8 @@ public:
inline
gimple_match_cond::gimple_match_cond (tree cond_in, tree else_value_in)
- : cond (cond_in), else_value (else_value_in)
+ : cond (cond_in), else_value (else_value_in), len (NULL_TREE),
+ bias (NULL_TREE)
{
}
--
2.41.0
