[gcc r14-9391] tree-optimization/114269 - 434.zeusmp regression after SCEV analysis fix

[Richard Biener]

https://gcc.gnu.org/g:018ddc86b928514d7dfee024dcdeb204d5dcdd61

commit r14-9391-g018ddc86b928514d7dfee024dcdeb204d5dcdd61
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Mar 8 13:27:12 2024 +0100

    tree-optimization/114269 - 434.zeusmp regression after SCEV analysis fix
    
    The following addresses a performance regression caused by the recent
    SCEV analysis fix with regard to folding multiplications and undefined
    behavior on overflow.  We do not handle (T) { a, +, b } * c but can
    treat sign-conversions from unsigned by performing the multiplication
    in the unsigned type.  That's what we already do for additions (but
    that misses one case that turns out important).
    
    This fixes the 434.zeusmp regression for me.
    
            PR tree-optimization/114269
            PR tree-optimization/114074
            * tree-chrec.cc (chrec_fold_plus_1): Handle sign-conversions
            in the third CASE_CONVERT case as well.
            (chrec_fold_multiply): Handle sign-conversions from unsigned
            by performing the operation in the unsigned type.

Diff:
---
 gcc/tree-chrec.cc | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/gcc/tree-chrec.cc b/gcc/tree-chrec.cc
index 2e6c7356d3b..7cd0ebc1010 100644
--- a/gcc/tree-chrec.cc
+++ b/gcc/tree-chrec.cc
@@ -325,6 +325,22 @@ chrec_fold_plus_1 (enum tree_code code, tree type,
 				    : build_int_cst_type (type, -1)));
 
 	CASE_CONVERT:
+	  {
+	    /* We can strip sign-conversions to signed by performing the
+	       operation in unsigned.  */
+	    tree optype = TREE_TYPE (TREE_OPERAND (op1, 0));
+	    if (INTEGRAL_TYPE_P (type)
+		&& INTEGRAL_TYPE_P (optype)
+		&& tree_nop_conversion_p (type, optype)
+		&& TYPE_UNSIGNED (optype))
+	      return chrec_convert (type,
+				    chrec_fold_plus_1 (code, optype,
+						       chrec_convert (optype,
+								      op0, NULL),
+						       TREE_OPERAND (op1, 0)),
+				    NULL);
+	  }
+
 	  if (tree_contains_chrecs (op1, NULL))
 	    return chrec_dont_know;
 	  /* FALLTHRU */
@@ -424,6 +440,22 @@ chrec_fold_multiply (tree type,
 	  return chrec_fold_multiply_poly_poly (type, op0, op1);
 
 	CASE_CONVERT:
+	  {
+	    /* We can strip sign-conversions to signed by performing the
+	       operation in unsigned.  */
+	    tree optype = TREE_TYPE (TREE_OPERAND (op1, 0));
+	    if (INTEGRAL_TYPE_P (type)
+		&& INTEGRAL_TYPE_P (optype)
+		&& tree_nop_conversion_p (type, optype)
+		&& TYPE_UNSIGNED (optype))
+	      return chrec_convert (type,
+				    chrec_fold_multiply (optype,
+							 chrec_convert (optype,
+									op0, NULL),
+							 TREE_OPERAND (op1, 0)),
+				    NULL);
+	  }
+
 	  if (tree_contains_chrecs (op1, NULL))
 	    return chrec_dont_know;
 	  /* FALLTHRU */
@@ -474,6 +506,22 @@ chrec_fold_multiply (tree type,
 	}
 
     CASE_CONVERT:
+      {
+	/* We can strip sign-conversions to signed by performing the
+	   operation in unsigned.  */
+	tree optype = TREE_TYPE (TREE_OPERAND (op0, 0));
+	if (INTEGRAL_TYPE_P (type)
+	    && INTEGRAL_TYPE_P (optype)
+	    && tree_nop_conversion_p (type, optype)
+	    && TYPE_UNSIGNED (optype))
+	  return chrec_convert (type,
+				chrec_fold_multiply (optype,
+						     TREE_OPERAND (op0, 0),
+						     chrec_convert (optype,
+								    op1, NULL)),
+				NULL);
+      }
+
       if (tree_contains_chrecs (op0, NULL))
 	return chrec_dont_know;
       /* FALLTHRU */