* [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT.
@ 2023-12-12 9:50 Jiahao Xu
2023-12-12 10:05 ` Xi Ruoyao
0 siblings, 1 reply; 4+ messages in thread
From: Jiahao Xu @ 2023-12-12 9:50 UTC (permalink / raw)
To: gcc-patches; +Cc: xry111, i, chenglulu, xuchenghua, Jiahao Xu
Define LOGICAL_OP_NON_SHORT_CIRCUIT as 0, for a short-circuit branch, use the
short-circuit operation instead of the non-short-circuit operation.
This gives a 1.8% improvement in SPECCPU 2017 fprate on 3A6000.
gcc/ChangeLog:
* config/loongarch/loongarch.h (LOGICAL_OP_NON_SHORT_CIRCUIT): Define.
gcc/testsuite/ChangeLog:
* gcc.target/loongarch/short-circuit.c: New test.
diff --git a/gcc/config/loongarch/loongarch.h b/gcc/config/loongarch/loongarch.h
index f1350b6048f..880c576c35b 100644
--- a/gcc/config/loongarch/loongarch.h
+++ b/gcc/config/loongarch/loongarch.h
@@ -869,6 +869,7 @@ typedef struct {
1 is the default; other values are interpreted relative to that. */
#define BRANCH_COST(speed_p, predictable_p) loongarch_branch_cost
+#define LOGICAL_OP_NON_SHORT_CIRCUIT 0
/* Return the asm template for a conditional branch instruction.
OPCODE is the opcode's mnemonic and OPERANDS is the asm template for
diff --git a/gcc/testsuite/gcc.target/loongarch/short-circuit.c b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
new file mode 100644
index 00000000000..2cef0193466
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple" } */
+
+int
+short_circuit (float *a)
+{
+ float t1x = a[0];
+ float t2x = a[1];
+ float t1y = a[2];
+ float t2y = a[3];
+ float t1z = a[4];
+ float t2z = a[5];
+
+ if (t1x > t2y || t2x < t1y || t1x > t2z || t2x < t1z || t1y > t2z || t2y < t1z)
+ return 0;
+
+ return 1;
+}
+/* { dg-final { scan-tree-dump-times "if" 6 "gimple" } } */
--
2.20.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT.
2023-12-12 9:50 [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT Jiahao Xu
@ 2023-12-12 10:05 ` Xi Ruoyao
2023-12-12 11:08 ` Jiahao Xu
0 siblings, 1 reply; 4+ messages in thread
From: Xi Ruoyao @ 2023-12-12 10:05 UTC (permalink / raw)
To: Jiahao Xu, gcc-patches; +Cc: i, chenglulu, xuchenghua
On Tue, 2023-12-12 at 17:50 +0800, Jiahao Xu wrote:
> diff --git a/gcc/testsuite/gcc.target/loongarch/short-circuit.c b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
> new file mode 100644
> index 00000000000..2cef0193466
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
> @@ -0,0 +1,19 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-gimple" } */
> +
> +int
> +short_circuit (float *a)
> +{
> + float t1x = a[0];
> + float t2x = a[1];
> + float t1y = a[2];
> + float t2y = a[3];
> + float t1z = a[4];
> + float t2z = a[5];
> +
> + if (t1x > t2y || t2x < t1y || t1x > t2z || t2x < t1z || t1y > t2z || t2y < t1z)
> + return 0;
> +
> + return 1;
> +}
> +/* { dg-final { scan-tree-dump-times "if" 6 "gimple" } } */
This test already passes without defining LOGICAL_OP_NON_SHORT_CIRCUIT.
Or am I missing something here?
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT.
2023-12-12 10:05 ` Xi Ruoyao
@ 2023-12-12 11:08 ` Jiahao Xu
2023-12-12 11:21 ` Xi Ruoyao
0 siblings, 1 reply; 4+ messages in thread
From: Jiahao Xu @ 2023-12-12 11:08 UTC (permalink / raw)
To: Xi Ruoyao, gcc-patches; +Cc: i, chenglulu, xuchenghua
在 2023/12/12 下午6:05, Xi Ruoyao 写道:
> On Tue, 2023-12-12 at 17:50 +0800, Jiahao Xu wrote:
>> diff --git a/gcc/testsuite/gcc.target/loongarch/short-circuit.c b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
>> new file mode 100644
>> index 00000000000..2cef0193466
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/loongarch/short-circuit.c
>> @@ -0,0 +1,19 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fdump-tree-gimple" } */
>> +
>> +int
>> +short_circuit (float *a)
>> +{
>> + float t1x = a[0];
>> + float t2x = a[1];
>> + float t1y = a[2];
>> + float t2y = a[3];
>> + float t1z = a[4];
>> + float t2z = a[5];
>> +
>> + if (t1x > t2y || t2x < t1y || t1x > t2z || t2x < t1z || t1y > t2z || t2y < t1z)
>> + return 0;
>> +
>> + return 1;
>> +}
>> +/* { dg-final { scan-tree-dump-times "if" 6 "gimple" } } */
> This test already passes without defining LOGICAL_OP_NON_SHORT_CIRCUIT.
> Or am I missing something here?
This test also needs to add the compilation option -ffast-math. I missed
it. Thanks for the reminder.
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT.
2023-12-12 11:08 ` Jiahao Xu
@ 2023-12-12 11:21 ` Xi Ruoyao
0 siblings, 0 replies; 4+ messages in thread
From: Xi Ruoyao @ 2023-12-12 11:21 UTC (permalink / raw)
To: Jiahao Xu, gcc-patches; +Cc: i, chenglulu, xuchenghua
On Tue, 2023-12-12 at 19:08 +0800, Jiahao Xu wrote:
> This test also needs to add the compilation option -ffast-math. I missed
> it. Thanks for the reminder.
In r14-15 we removed LOGICAL_OP_NON_SHORT_CIRCUIT definition because the
default value (1 for all current LoongArch CPUs with branch_cost = 6)
may reduce the number of conditional branch instructions.
I guess here the problem is floating-point compare instruction is much
more costly than other instructions but the fact is not correctly
modeled yet. Could you try
https://gcc.gnu.org/pipermail/gcc-patches/2023-December/640012.html
where I've raised fp_add cost (which is used for estimating floating-
point compare cost) to 5 instructions and see if it solves your problem
without LOGICAL_OP_NON_SHORT_CIRCUIT?
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-12-12 9:50 [PATCH] LoongArch: Define LOGICAL_OP_NON_SHORT_CIRCUIT Jiahao Xu
2023-12-12 10:05 ` Xi Ruoyao
2023-12-12 11:08 ` Jiahao Xu
2023-12-12 11:21 ` Xi Ruoyao
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