Re: [PATCH] Avoid extending lifetime of likely spilled hard regs in ifcvt before reload (PR rtl-optimization/56484)
On Tue, Mar 05, 2013 at 11:03:13PM +0100, Jakub Jelinek wrote:
> > ifcvt.c tests only small_register_classes_for_mode_p in the other places,
> > so
> > do you really need class_likely_spilled_p here?
>
> I guess I don't. I've grepped for small_register_classes_for_mode_p and
> didn't see
> anything in i386, so I figured out that it would be using a default (which
> is false). But apparently it uses hook_bool_mode_true, so it is a superset
> of class_likely_spilled_p, guess I can leave that out.
Here is what I've actually committed (I've also removed the
!reload_completed &&, because noce_process_if_block is only called for
!!reload_completed (the only caller asserts it)).
2013-03-05 Jakub Jelinek
PR rtl-optimization/56484
* ifcvt.c (noce_process_if_block): If else_bb is NULL, avoid extending
lifetimes of hard registers on small register class machines.
* gcc.c-torture/compile/pr56484.c: New test.
--- gcc/ifcvt.c.jj 2013-03-05 15:12:15.284564443 +0100
+++ gcc/ifcvt.c 2013-03-05 23:11:25.751625601 +0100
@@ -2491,6 +2491,12 @@ noce_process_if_block (struct noce_if_in
|| ! noce_operand_ok (SET_SRC (set_b))
|| reg_overlap_mentioned_p (x, SET_SRC (set_b))
|| modified_between_p (SET_SRC (set_b), insn_b, jump)
+ /* Avoid extending the lifetime of hard registers on small
+register class machines. */
+ || (REG_P (SET_SRC (set_b))
+ && HARD_REGISTER_P (SET_SRC (set_b))
+ && targetm.small_register_classes_for_mode_p
+ (GET_MODE (SET_SRC (set_b
/* Likewise with X. In particular this can happen when
noce_get_condition looks farther back in the instruction
stream than one might expect. */
--- gcc/testsuite/gcc.c-torture/compile/pr56484.c.jj2013-03-05
16:57:50.416961638 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr56484.c 2013-03-05
16:57:50.417961672 +0100
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/56484 */
+
+unsigned char b[4096];
+int bar (void);
+
+int
+foo (void)
+{
+ int a = 0;
+ while (bar ())
+{
+ int c = bar ();
+ a = a < 0 ? a : c;
+ __builtin_memset (b, 0, sizeof b);
+}
+ return a;
+}
Jakub
Re: [PATCH] Avoid extending lifetime of likely spilled hard regs in ifcvt before reload (PR rtl-optimization/56484)
On Tue, Mar 05, 2013 at 06:28:13PM +0100, Eric Botcazou wrote: > > Without this patch, ifcvt extends lifetime of %eax hard register, > > which causes reload/LRA ICE later on. Combiner and other passes try hard > > not to do that, even ifcvt has code for it if x is a hard register a few > > lines below it, but in this case the hard register is SET_SRC (set_b). > > > > With this patch we just use the pseudo (x) which has been initialized > > from the hard register before the conditional. > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > > > 2013-03-05 Jakub Jelinek > > > > PR rtl-optimization/56484 > > * ifcvt.c (noce_process_if_block): Before reload if else_bb > > is NULL, avoid extending lifetimes of hard registers in > > likely to spilled or small register classes. > > ifcvt.c tests only small_register_classes_for_mode_p in the other places, so > do you really need class_likely_spilled_p here? I guess I don't. I've grepped for small_register_classes_for_mode_p and didn't see anything in i386, so I figured out that it would be using a default (which is false). But apparently it uses hook_bool_mode_true, so it is a superset of class_likely_spilled_p, guess I can leave that out. Jakub
Re: [PATCH] Avoid extending lifetime of likely spilled hard regs in ifcvt before reload (PR rtl-optimization/56484)
> Without this patch, ifcvt extends lifetime of %eax hard register, > which causes reload/LRA ICE later on. Combiner and other passes try hard > not to do that, even ifcvt has code for it if x is a hard register a few > lines below it, but in this case the hard register is SET_SRC (set_b). > > With this patch we just use the pseudo (x) which has been initialized > from the hard register before the conditional. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > 2013-03-05 Jakub Jelinek > > PR rtl-optimization/56484 > * ifcvt.c (noce_process_if_block): Before reload if else_bb > is NULL, avoid extending lifetimes of hard registers in > likely to spilled or small register classes. ifcvt.c tests only small_register_classes_for_mode_p in the other places, so do you really need class_likely_spilled_p here? -- Eric Botcazou
Re: [PATCH] Avoid extending lifetime of likely spilled hard regs in ifcvt before reload (PR rtl-optimization/56484)
On 03/05/2013 09:26 AM, Jakub Jelinek wrote: Hi! Without this patch, ifcvt extends lifetime of %eax hard register, which causes reload/LRA ICE later on. Combiner and other passes try hard not to do that, even ifcvt has code for it if x is a hard register a few lines below it, but in this case the hard register is SET_SRC (set_b). With this patch we just use the pseudo (x) which has been initialized from the hard register before the conditional. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2013-03-05 Jakub Jelinek PR rtl-optimization/56484 * ifcvt.c (noce_process_if_block): Before reload if else_bb is NULL, avoid extending lifetimes of hard registers in likely to spilled or small register classes. OK. Jeff
