[PATCH] s390: Change costs for load on condition.

[PATCH] s390: Change costs for load on condition.

[Robin Dapp]

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Hi,

this patch is a follow-up patch to the recent ifcvt changes. It
increased costs for a load on condition to 6.  This ensures that we
if-convert sequences of three regular instructions (of cost 4) e.g. a
compare and two SETs into two loads on condition (of cost 6).  With a
cost of 5, four-insn sequences (three SETs) would also be if-converted.

The adjustment to the mov[qi/si]cc expander makes sure we if-convert a
QImode/bool.  Before, combine would create a paradoxical subreg itself
but need an additional insn.

Bootstrapped and regtested on s390x.

Is it OK?

Regards
 Robin

--

gcc/ChangeLog:

	* config/s390/s390.cc (s390_rtx_costs): Increase costs for load
	on condition.
	* config/s390/s390.md: Change mov[qi/si]cc expander.

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commit b246f96c2a2813d0e509e7916744cda07cc5131c
Author: Robin Dapp <rdapp@linux.ibm.com>
Date:   Fri Jun 18 10:51:22 2021 +0200

    s390: Increase costs for load on condition and change movqicc expander.

diff --git a/gcc/config/s390/s390.cc b/gcc/config/s390/s390.cc
index 43c5c72554a..f2e4474df99 100644
--- a/gcc/config/s390/s390.cc
+++ b/gcc/config/s390/s390.cc
@@ -3636,7 +3636,7 @@ s390_rtx_costs (rtx x, machine_mode mode, int outer_code,
 
 	/* It is going to be a load/store on condition.  Make it
 	   slightly more expensive than a normal load.  */
-	*total = COSTS_N_INSNS (1) + 1;
+	*total = COSTS_N_INSNS (1) + 2;
 
 	rtx dst = SET_DEST (x);
 	rtx then = XEXP (SET_SRC (x), 1);
diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md
index e3ccbac58c0..5eee8e86b42 100644
--- a/gcc/config/s390/s390.md
+++ b/gcc/config/s390/s390.md
@@ -7003,9 +7003,9 @@
   if (!CONSTANT_P (els))
     els = simplify_gen_subreg (E_SImode, els, <MODE>mode, 0);
 
-  rtx tmp_target = gen_reg_rtx (E_SImode);
+  rtx tmp_target = simplify_gen_subreg (E_SImode, operands[0], <MODE>mode, 0);
+
   emit_insn (gen_movsicc (tmp_target, operands[1], then, els));
-  emit_move_insn (operands[0], gen_lowpart (<MODE>mode, tmp_target));
   DONE;
 })
 

Re: [PATCH] s390: Change costs for load on condition.

[Andreas Krebbel]

On 1/20/22 11:10, Robin Dapp wrote:
> Hi,
> 
> this patch is a follow-up patch to the recent ifcvt changes. It
> increased costs for a load on condition to 6.  This ensures that we
> if-convert sequences of three regular instructions (of cost 4) e.g. a
> compare and two SETs into two loads on condition (of cost 6).  With a
> cost of 5, four-insn sequences (three SETs) would also be if-converted.
> 
> The adjustment to the mov[qi/si]cc expander makes sure we if-convert a
> QImode/bool.  Before, combine would create a paradoxical subreg itself
> but need an additional insn.
> 
> Bootstrapped and regtested on s390x.
> 
> Is it OK?
> 
> Regards
>  Robin
> 
> --
> 
> gcc/ChangeLog:
> 
> 	* config/s390/s390.cc (s390_rtx_costs): Increase costs for load
> 	on condition.
> 	* config/s390/s390.md: Change mov[qi/si]cc expander.

Could you please add two tests for the sequences which are improved here. Just to make sure we get
aware once it breaks again.

Patch is ok. Thanks!

Andreas

Re: [PATCH] s390: Change costs for load on condition.

[Robin Dapp]

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> Patch is ok. Thanks!

As discussed off-list, committed as attached.

Regards
 Robin

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commit 1e3185e714e877b2b4d14ade0865322f71a8cbf6
Author: Robin Dapp <rdapp@linux.ibm.com>
Date:   Tue Feb 8 14:56:29 2022 +0100

    s390: Increase costs for load on condition and change movqicc expander.
    
    This patch changes the costs for a load on condition from 5 to 6 in
    order to ensure that we only if-convert two and not three or more SETS like
    
    if (cond)
    {
      a = b;
      c = d;
      e = f;
    }
    
    In the movqicc expander we emit a paradoxical subreg directly that
    combine would otherwise try to create by using a non-optimal sequence
    (which would be too expensive).
    
    Also, fix two oversights in ifcvt testcases.
    
    gcc/ChangeLog:
    
            * config/s390/s390.cc (s390_rtx_costs): Increase costs for load
            on condition.
            * config/s390/s390.md: Use paradoxical subreg.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/s390/ifcvt-two-insns-int.c: Fix array size.
            * gcc.target/s390/ifcvt-two-insns-long.c: Dito.

diff --git a/gcc/config/s390/s390.cc b/gcc/config/s390/s390.cc
index c6cfe41ad7b..d2af6d8813d 100644
--- a/gcc/config/s390/s390.cc
+++ b/gcc/config/s390/s390.cc
@@ -3636,7 +3636,7 @@ s390_rtx_costs (rtx x, machine_mode mode, int outer_code,
 
 	/* It is going to be a load/store on condition.  Make it
 	   slightly more expensive than a normal load.  */
-	*total = COSTS_N_INSNS (1) + 1;
+	*total = COSTS_N_INSNS (1) + 2;
 
 	rtx dst = SET_DEST (x);
 	rtx then = XEXP (SET_SRC (x), 1);
diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md
index e3ccbac58c0..5eee8e86b42 100644
--- a/gcc/config/s390/s390.md
+++ b/gcc/config/s390/s390.md
@@ -7003,9 +7003,9 @@
   if (!CONSTANT_P (els))
     els = simplify_gen_subreg (E_SImode, els, <MODE>mode, 0);
 
-  rtx tmp_target = gen_reg_rtx (E_SImode);
+  rtx tmp_target = simplify_gen_subreg (E_SImode, operands[0], <MODE>mode, 0);
+
   emit_insn (gen_movsicc (tmp_target, operands[1], then, els));
-  emit_move_insn (operands[0], gen_lowpart (<MODE>mode, tmp_target));
   DONE;
 })
 
diff --git a/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-int.c b/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-int.c
index 1ced7107de0..031cc433f56 100644
--- a/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-int.c
+++ b/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-int.c
@@ -5,7 +5,6 @@
 
 /* { dg-final { scan-assembler "lochinle\t%r.?,1" } } */
 /* { dg-final { scan-assembler "locrnle\t.*" } } */
-#include <stdbool.h>
 #include <limits.h>
 #include <stdio.h>
 #include <assert.h>
@@ -33,7 +32,7 @@ int main()
 {
   int a[] = {2, 1, -13, INT_MAX, INT_MIN, 0};
 
-  int res = foo (a, sizeof (a));
+  int res = foo (a, sizeof (a) / sizeof (a[0]));
 
   assert (res == (INT_MIN + 1));
 }
diff --git a/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-long.c b/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-long.c
index 5a1173fc6ef..cd04d2ad33e 100644
--- a/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-long.c
+++ b/gcc/testsuite/gcc.target/s390/ifcvt-two-insns-long.c
@@ -5,7 +5,6 @@
 
 /* { dg-final { scan-assembler "locghinle\t%r.?,1" } } */
 /* { dg-final { scan-assembler "locgrnle\t.*" } } */
-#include <stdbool.h>
 #include <limits.h>
 #include <stdio.h>
 #include <assert.h>
@@ -33,7 +32,7 @@ int main()
 {
   long a[] = {2, 1, -13, LONG_MAX, LONG_MIN, 0};
 
-  long res = foo (a, sizeof (a));
+  long res = foo (a, sizeof (a) / sizeof (a[0]));
 
   assert (res == (LONG_MIN + 1));
 }