From: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
Date: Thu, 15 Jan 2026 00:44:17 +0000 (-0800)
Subject: slsr: Fix some undefined/overflow introducing bugs in SLSR [PR106883]
X-Git-Tag: basepoints/gcc-17~1804
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e5bcb08d132bf753178a2b30962b4a9d3452c4f2;p=thirdparty%2Fgcc.git

slsr: Fix some undefined/overflow introducing bugs in SLSR [PR106883]

This fixes the first part of SLSR incorrectly inserting undefined code (overflow)
into the IR. The easiest way is to rewrite the statement after creating it
using rewrite_to_defined_unconditional.
This fixes the testcases from PR 121347 (and a few others) which all cause an
infinite loops to appear.
I will be posting the fix for replace_rhs_if_not_dup later and at that point I
will add a few testcases.

Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/121347
	PR tree-optimization/106883
gcc/ChangeLog:

	* gimple-ssa-strength-reduction.cc (insert_initializers): Rewrite
	newly inserted statements for undefinedness (overflow).

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
---

diff --git a/gcc/gimple-ssa-strength-reduction.cc b/gcc/gimple-ssa-strength-reduction.cc
index 70978b295d8..3bb924fa54c 100644
--- a/gcc/gimple-ssa-strength-reduction.cc
+++ b/gcc/gimple-ssa-strength-reduction.cc
@@ -57,6 +57,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-eh.h"
 #include "builtins.h"
 #include "tree-ssa-dce.h"
+#include "gimple-fold.h"
 
 /* Information about a strength reduction candidate.  Each statement
    in the candidate table represents an expression of one of the
@@ -3474,8 +3475,15 @@ insert_initializers (slsr_cand_t c)
 	      gimple_set_location (cast_stmt, loc);
 	    }
 
-	  gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT);
 	  gimple_set_location (init_stmt, loc);
+	  if (gimple_needing_rewrite_undefined (init_stmt))
+	    {
+	      gimple_seq seq;
+	      seq = rewrite_to_defined_unconditional (init_stmt);
+	      gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
+	    }
+	  else
+	    gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT);
 	}
       else
 	{
@@ -3483,6 +3491,7 @@ insert_initializers (slsr_cand_t c)
 	  gimple *basis_stmt = lookup_cand (c->basis)->cand_stmt;
 	  location_t loc = gimple_location (basis_stmt);
 
+	  gimple_set_location (init_stmt, gimple_location (basis_stmt));
 	  if (!gsi_end_p (gsi) && stmt_ends_bb_p (gsi_stmt (gsi)))
 	    {
 	      if (cast_stmt)
@@ -3490,7 +3499,14 @@ insert_initializers (slsr_cand_t c)
 		  gsi_insert_before (&gsi, cast_stmt, GSI_SAME_STMT);
 		  gimple_set_location (cast_stmt, loc);
 		}
-	      gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT);
+	      if (gimple_needing_rewrite_undefined (init_stmt))
+		{
+		  gimple_seq seq;
+		  seq = rewrite_to_defined_unconditional (init_stmt);
+		  gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
+		}
+	      else
+		gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT);
 	    }
 	  else
 	    {
@@ -3499,10 +3515,15 @@ insert_initializers (slsr_cand_t c)
 		  gsi_insert_after (&gsi, cast_stmt, GSI_NEW_STMT);
 		  gimple_set_location (cast_stmt, loc);
 		}
-	      gsi_insert_after (&gsi, init_stmt, GSI_NEW_STMT);
+	      if (gimple_needing_rewrite_undefined (init_stmt))
+		{
+		  gimple_seq seq;
+		  seq = rewrite_to_defined_unconditional (init_stmt);
+		  gsi_insert_seq_after (&gsi, seq, GSI_SAME_STMT);
+		}
+	      else
+		gsi_insert_after (&gsi, init_stmt, GSI_SAME_STMT);
 	    }
-
-	  gimple_set_location (init_stmt, gimple_location (basis_stmt));
 	}
 
       if (dump_file && (dump_flags & TDF_DETAILS))