loop-invariant: Split preheader edge if the preheader bb ends with jump [PR106751]
Commit Message
Hi!
The RTL loop passes only request simple preheaders, but don't require
fallthru preheaders, while move_invariant_reg apparently assumes the
latter, that it can just append instruction(s) to the end of the preheader
basic block.
The following patch fixes that by splitting the preheader edge if
the preheader bb ends with a JUMP_INSN (asm goto in this case).
Without that we get control flow in the middle of a bb.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-12-16 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/106751
* loop-invariant.cc (move_invariant_reg): If preheader bb ends
with a JUMP_INSN, split the preheader edge and emit invariants
into the new preheader basic block.
* gcc.c-torture/compile/pr106751.c: New test.
Jakub
Comments
On Fri, 16 Dec 2022, Jakub Jelinek wrote:
> Hi!
>
> The RTL loop passes only request simple preheaders, but don't require
> fallthru preheaders, while move_invariant_reg apparently assumes the
> latter, that it can just append instruction(s) to the end of the preheader
> basic block.
>
> The following patch fixes that by splitting the preheader edge if
> the preheader bb ends with a JUMP_INSN (asm goto in this case).
> Without that we get control flow in the middle of a bb.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2022-12-16 Jakub Jelinek <jakub@redhat.com>
>
> PR rtl-optimization/106751
> * loop-invariant.cc (move_invariant_reg): If preheader bb ends
> with a JUMP_INSN, split the preheader edge and emit invariants
> into the new preheader basic block.
>
> * gcc.c-torture/compile/pr106751.c: New test.
>
> --- gcc/loop-invariant.cc.jj 2022-01-18 11:58:59.683980614 +0100
> +++ gcc/loop-invariant.cc 2022-12-15 17:14:32.906883258 +0100
> @@ -1837,6 +1837,8 @@ move_invariant_reg (class loop *loop, un
> else if (dump_file)
> fprintf (dump_file, "Invariant %d moved without introducing a new "
> "temporary register\n", invno);
> + if (JUMP_P (BB_END (preheader)))
> + preheader = split_edge (loop_preheader_edge (loop));
> reorder_insns (inv->insn, inv->insn, BB_END (preheader));
> df_recompute_luids (preheader);
>
> --- gcc/testsuite/gcc.c-torture/compile/pr106751.c.jj 2022-12-15 17:44:35.602519711 +0100
> +++ gcc/testsuite/gcc.c-torture/compile/pr106751.c 2022-12-15 17:44:21.789721827 +0100
> @@ -0,0 +1,17 @@
> +/* PR rtl-optimization/106751 */
> +
> +int *foo (void);
> +
> +void
> +bar (void)
> +{
> + asm goto ("" : : : : lab);
> + __builtin_unreachable ();
> +lab:
> + while (1)
> + {
> + int o;
> + asm ("" : "=r" (o) : "g" (1));
> + *foo () = o;
> + }
> +}
>
> Jakub
>
>
@@ -1837,6 +1837,8 @@ move_invariant_reg (class loop *loop, un
else if (dump_file)
fprintf (dump_file, "Invariant %d moved without introducing a new "
"temporary register\n", invno);
+ if (JUMP_P (BB_END (preheader)))
+ preheader = split_edge (loop_preheader_edge (loop));
reorder_insns (inv->insn, inv->insn, BB_END (preheader));
df_recompute_luids (preheader);
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/106751 */
+
+int *foo (void);
+
+void
+bar (void)
+{
+ asm goto ("" : : : : lab);
+ __builtin_unreachable ();
+lab:
+ while (1)
+ {
+ int o;
+ asm ("" : "=r" (o) : "g" (1));
+ *foo () = o;
+ }
+}