From: Tamar Christina <tamar.christina@arm.com>
Date: Sun, 24 Dec 2023 19:17:13 +0000 (+0000)
Subject: middle-end: prevent LIM from hoising vector compares from gconds if target does not... 
X-Git-Tag: basepoints/gcc-15~3318
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1dcc0fe371e3cb10d2cbe3f6c88db6f72edddda;p=thirdparty%2Fgcc.git

middle-end: prevent LIM from hoising vector compares from gconds if target does not support it.

LIM notices that in some cases the condition and the results are loop
invariant and tries to move them out of the loop.

While the resulting code is operationally sound, moving the compare out of the
gcond results in generating code that no longer branches, so cbranch is no
longer applicable.  As such I now add code to check during this motion to see
if the target supports flag setting vector comparison as general operation.

I have tried writing a GIMPLE testcase for this but the gimple FE seems to be
having some trouble with the vector types.  It seems to fail parsing.

The early break code testsuite however has a test for this
(vect-early-break_67.c).

gcc/ChangeLog:

	* tree-ssa-loop-im.cc (determine_max_movement): Import insn-codes.h
	and optabs-tree.h and check for vector compare motion out of gcond.
---

diff --git a/gcc/tree-ssa-loop-im.cc b/gcc/tree-ssa-loop-im.cc
index 396963b6754c..2ebf6d6548c4 100644
--- a/gcc/tree-ssa-loop-im.cc
+++ b/gcc/tree-ssa-loop-im.cc
@@ -48,6 +48,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-dfa.h"
 #include "tree-ssa.h"
 #include "dbgcnt.h"
+#include "insn-codes.h"
+#include "optabs-tree.h"
 
 /* TODO:  Support for predicated code motion.  I.e.
 
@@ -852,6 +854,17 @@ determine_max_movement (gimple *stmt, bool must_preserve_exec)
 	  if (!extract_true_false_args_from_phi (dom, phi, NULL, NULL))
 	    return false;
 
+	/* Check if one of the depedent statement is a vector compare whether
+	   the target supports it,  otherwise it's invalid to hoist it out of
+	   the gcond it belonged to.  */
+	if (VECTOR_TYPE_P (TREE_TYPE (gimple_cond_lhs (cond))))
+	  {
+	    tree type = TREE_TYPE (gimple_cond_lhs (cond));
+	    auto code = gimple_cond_code (cond);
+	    if (!target_supports_op_p (type, code, optab_vector))
+	      return false;
+	  }
+
 	  /* Fold in dependencies and cost of the condition.  */
 	  FOR_EACH_SSA_TREE_OPERAND (val, cond, iter, SSA_OP_USE)
 	    {