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.c (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.

(cherry picked from commit c2d9159717b474f9c06dde4d32b48b87164deb50)

diff --git a/gcc/optabs.c b/gcc/optabs.c
index 049a18ceb7c1d8e12cc1251fd48321e1c191a3a9..64f23d2c293725375e0eabae6fcc42cd3d3fd27a 100644 (file)
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -3891,12 +3891,14 @@ 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);
 
 #if HAVE_cc0
@@ -3972,6 +3974,8 @@ 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 ();
+}