[gcc r14-307] PHIOPT: Allow MIN/MAX to have up to 2 MIN/MAX expressions for early phiopt

[Andrew Pinski <pinskia@gcc.gnu.org>]

https://gcc.gnu.org/g:82f4f90a3761848ac71cee4fc607483572c0b34b

commit r14-307-g82f4f90a3761848ac71cee4fc607483572c0b34b
Author: Andrew Pinski <apinski@marvell.com>
Date:   Sat Apr 1 04:59:11 2023 +0000

    PHIOPT: Allow MIN/MAX to have up to 2 MIN/MAX expressions for early phiopt
    
    In the early PHIOPT mode, the original minmax_replacement, would
    replace a PHI node with up to 2 min/max expressions in some cases,
    this allows for that too.
    
    OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
    
    gcc/ChangeLog:
    
            * tree-ssa-phiopt.cc (phiopt_early_allow): Allow for
            up to 2 min/max expressions in the sequence/match code.

Diff:
---
 gcc/tree-ssa-phiopt.cc | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index 5ab23b54ed6..7fc6ac17b4a 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -533,9 +533,23 @@ phiopt_early_allow (gimple_seq &seq, gimple_match_op &op)
     return false;
   tree_code code = (tree_code)op.code;
 
-  /* For non-empty sequence, only allow one statement.  */
+  /* For non-empty sequence, only allow one statement
+     except for MIN/MAX, allow max 2 statements,
+     each with MIN/MAX.  */
   if (!gimple_seq_empty_p (seq))
     {
+      if (code == MIN_EXPR || code == MAX_EXPR)
+	{
+	  if (!gimple_seq_singleton_p (seq))
+	    return false;
+
+	  gimple *stmt = gimple_seq_first_stmt (seq);
+	  /* Only allow assignments.  */
+	  if (!is_gimple_assign (stmt))
+	    return false;
+	  code = gimple_assign_rhs_code (stmt);
+	  return code == MIN_EXPR || code == MAX_EXPR;
+	}
       /* Check to make sure op was already a SSA_NAME.  */
       if (code != SSA_NAME)
 	return false;