optabs: Don't create pseudos in prepare_cmp_insn when not allowed [PR102478]

cond traps can be created during ce3 after reload (and e.g. PR103028
recently fixed some ce3 cond trap related bug, so I think often that
works fine and we shouldn't disable cond traps after RA altogether),
but it calls prepare_cmp_insn.  This function can fail, so I don't
see why we couldn't make it work after RA (in most cases it already
just works).  The first hunk is just an optimization which doesn't
make sense after RA, so I've guarded it with can_create_pseudo_p.
The second hunk is just a theoretical case, I don't have a testcase for it.
prepare_cmp_insn has some other spots that can create pseudos, like when
both operands have VOIDmode, or when it is BLKmode comparison, or
not OPTAB_DIRECT, but I think none of that applies to ce3, we punt on
BLKmode earlier, use OPTAB_DIRECT and shouldn't be comparing two
VOIDmode CONST_INTs.

2022-01-21  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/102478
	* optabs.cc (prepare_cmp_insn): If !can_create_pseudo_p (), don't
	force_reg constants and for -fnon-call-exceptions fail if copy_to_reg
	would be needed.

	* gcc.dg/pr102478.c: New test.

diff --git a/gcc/optabs.cc b/gcc/optabs.cc
index 2486e1489609c1af5185f1452ef988ffe372336f..3d8fa3abdfeaf245fd0ca5b2e5765502bfc54d6c 100644 (file)
--- a/gcc/optabs.cc
+++ b/gcc/optabs.cc
@@ -4398,12 +4398,14 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx_code comparison, rtx size,
   /* If we are optimizing, force expensive constants into a register.  */
   if (CONSTANT_P (x) && optimize
       && (rtx_cost (x, mode, COMPARE, 0, optimize_insn_for_speed_p ())
-          > COSTS_N_INSNS (1)))
+          > COSTS_N_INSNS (1))
+      && can_create_pseudo_p ())
     x = force_reg (mode, x);
 
   if (CONSTANT_P (y) && optimize
       && (rtx_cost (y, mode, COMPARE, 1, optimize_insn_for_speed_p ())
-          > COSTS_N_INSNS (1)))
+          > COSTS_N_INSNS (1))
+      && can_create_pseudo_p ())
     y = force_reg (mode, y);
 
   /* Don't let both operands fail to indicate the mode.  */
@@ -4472,6 +4474,8 @@ prepare_cmp_insn (rtx x, rtx y, enum rtx_code comparison, rtx size,
      compare and branch in different basic blocks.  */
   if (cfun->can_throw_non_call_exceptions)
     {
+      if (!can_create_pseudo_p () && (may_trap_p (x) || may_trap_p (y)))
+       goto fail;
       if (may_trap_p (x))
        x = copy_to_reg (x);
       if (may_trap_p (y))

diff --git a/gcc/testsuite/gcc.dg/pr102478.c b/gcc/testsuite/gcc.dg/pr102478.c
new file mode 100644 (file)
index 0000000..43bc49b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr102478.c
@@ -0,0 +1,29 @@
+/* PR rtl-optimization/102478 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-if-conversion -Wno-div-by-zero" } */
+
+unsigned a, b, c;
+
+void
+foo (void)
+{
+  c |= __builtin_expect (65535 / a, 0) && 0 / 0;
+  b = 0;
+}
+
+void
+bar (void)
+{
+  if (a <= 65535)
+    __builtin_trap ();
+  b = 0;
+}
+
+void
+baz (void)
+{
+  if (a > 65535)
+    b = 0;
+  else
+    __builtin_trap ();
+}