From: Manolis Tsamis <manolis.tsamis@vrull.eu>
Date: Tue, 20 Aug 2024 07:16:29 +0000 (+0200)
Subject: ifcvt: Do not overwrite results in noce_convert_multiple_sets [PR116372, PR116405]
X-Git-Tag: basepoints/gcc-16~6415
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a9f5e23aba1a6f4ec32f1147b340a8145d827da9;p=thirdparty%2Fgcc.git

ifcvt: Do not overwrite results in noce_convert_multiple_sets [PR116372, PR116405]

Now that more operations are allowed for noce_convert_multiple_sets,
it is possible that the same register appears multiple times as target
in a basic block.  After noce_convert_multiple_sets_1 is called we
potentially also emit register moves from temporaries back to the
original targets.  In some cases where the target registers overlap
with the block's condition, these register moves may overwrite
intermediate variables because they're emitted after the if-converted
code.  To address this issue we now iterate backwards and keep track
of seen registers when emitting these final register moves.

	PR rtl-optimization/116372
	PR rtl-optimization/116405

gcc/ChangeLog:

	* ifcvt.cc (noce_convert_multiple_sets): Iterate backwards and track
	target registers.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr116372.c: New test.
	* gcc.dg/pr116405.c: New test.
---

diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index b136d7dbbba..6487574c514 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -3515,10 +3515,24 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
      given an empty BB to convert, and we can't handle that.  */
   gcc_assert (!insn_info.is_empty ());
 
-  /* Now fixup the assignments.  */
-  for (unsigned i = 0; i < insn_info.length (); i++)
-    if (insn_info[i]->target != insn_info[i]->temporary)
-      noce_emit_move_insn (insn_info[i]->target, insn_info[i]->temporary);
+  /* Now fixup the assignments.
+     PR116405: Iterate in reverse order and keep track of the targets so that
+     a move does not overwrite a subsequent value when multiple instructions
+     have the same target.  */
+  unsigned i;
+  noce_multiple_sets_info *info;
+  bitmap set_targets = BITMAP_ALLOC (&reg_obstack);
+  FOR_EACH_VEC_ELT_REVERSE (insn_info, i, info)
+    {
+      gcc_checking_assert (REG_P (info->target));
+
+      if (info->target != info->temporary
+	  && !bitmap_bit_p (set_targets, REGNO (info->target)))
+	noce_emit_move_insn (info->target, info->temporary);
+
+      bitmap_set_bit (set_targets, REGNO (info->target));
+    }
+  BITMAP_FREE (set_targets);
 
   /* Actually emit the sequence if it isn't too expensive.  */
   rtx_insn *seq = get_insns ();
diff --git a/gcc/testsuite/gcc.dg/pr116372.c b/gcc/testsuite/gcc.dg/pr116372.c
new file mode 100644
index 00000000000..e9878ac5042
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr116372.c
@@ -0,0 +1,13 @@
+/* PR rtl-optimization/116372 */
+/* { dg-do run } */
+/* { dg-options "-O1" } */ 
+/* { dg-additional-options "-march=z13" { target s390x-*-* } } */
+
+long x = -0x7fffffff - 1;
+int main (void)
+{
+  long y = x % (-0xf - 1);
+  if (-0x7fffffff - 1 + y == x == 0)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/pr116405.c b/gcc/testsuite/gcc.dg/pr116405.c
new file mode 100644
index 00000000000..9223f15a298
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr116405.c
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/116405 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-ssa-phiopt -fno-tree-dce" } */ 
+
+int printf(const char *, ...);
+int a, b = 2, c = 1;
+unsigned d, e;
+int main() {
+ L:
+  a = -1 / c;
+  d = ~(b && (c && ~e) & b);
+  printf("0\n");
+  c = 0;
+  if (d != -1)
+    goto L;
+  return 0;
+}