rtl-ssa: Add missing live-out uses [PR121619]

This PR is another bug in the rtl-ssa code to manage live-out uses.
It seems that this didn't get much coverage until recently.

In the testcase, late-combine first removed a register-to-register
move by substituting into all uses, some of which were in other EBBs.
This was done after checking make_uses_available, which (as expected)
says that single dominating definitions are available everywhere
that the definition dominates.  But the update failed to add
appropriate live-out uses, so a later parallelisation attempt
tried to move the new destination into a later block.

gcc/
	PR rtl-optimization/121619
	* rtl-ssa/functions.h (function_info::commit_make_use_available):
	Declare.
	* rtl-ssa/blocks.cc (function_info::commit_make_use_available):
	New function.
	* rtl-ssa/changes.cc (function_info::apply_changes_to_insn): Use it.

gcc/testsuite/
	PR rtl-optimization/121619
	* gcc.dg/pr121619.c: New test.

1 files changed, 33 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/pr121619.c b/gcc/testsuite/gcc.dg/pr121619.c
new file mode 100644
index 0000000..a63896d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr121619.c
@@ -0,0 +1,33 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fno-gcse -fno-tree-ter -fno-guess-branch-probability -fno-forward-propagate" } */
+
+int printf(const char *, ...);
+long a, c, d;
+char b;
+int main() {
+f : {
+  short g = 100;
+  int h = 1;
+  while (1) {
+    char i = 0;
+    if (a)
+      i = h = -b;
+    short j = g;
+    c = h ^ g;
+    g = ~(-h / c + 1);
+    if (b > 6) {
+      a = g && -1;
+      goto f;
+    }
+    if (j < 100)
+      printf("%ld\n", d);
+    if (g - 1)
+      break;
+    b = i;
+  }
+  int k = 2L % g;
+  if (k)
+    goto f;
+  }
+  return 0;
+}