[PATCH] [MIPS] Remove unnecessary moves around DSP multiply-accumulate instructions

[PATCH] [MIPS] Remove unnecessary moves around DSP multiply-accumulate instructions

[Mihailo Stojanovic]

Unnecessary moves around dpadd and dpsub are caused by different pseudos
being assigned to the input-output operands which correspond to the same
register.

Just like for the MSA multiply-accumulate instructions, this forces the
same pseudo to the input-output operands,
which removes unnecesary moves.

Tested on mips-mti-linux-gnu.

gcc/ChangeLog:

        * gcc/config/mips/mips.c (mips_expand_builtin_insn): Operands of
        DSP multiply-accumulate instructions which correspond to the
        same input-output register now have the same pseudo asigned to
        them.

gcc/testsuite/ChangeLog:

        * gcc/testsuite/gcc.target/mips/mac-zero-reload.c: New test.
---
 gcc/config/mips/mips.c                          | 24 +++++++++++++++++++
 gcc/testsuite/gcc.target/mips/mac-zero-reload.c | 32 +++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/mips/mac-zero-reload.c

diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c
index e337b82..3aa2c11 100644
--- a/gcc/config/mips/mips.c
+++ b/gcc/config/mips/mips.c
@@ -16994,6 +16994,30 @@ mips_expand_builtin_insn (enum insn_code icode, unsigned int nops,
     case CODE_FOR_msa_dpsub_u_w:
     case CODE_FOR_msa_dpsub_u_h:
     case CODE_FOR_msa_dpsub_u_d:
+
+    case CODE_FOR_mips_dpau_h_qbl:
+    case CODE_FOR_mips_dpau_h_qbr:
+    case CODE_FOR_mips_dpsu_h_qbl:
+    case CODE_FOR_mips_dpsu_h_qbr:
+    case CODE_FOR_mips_dpaq_s_w_ph:
+    case CODE_FOR_mips_dpsq_s_w_ph:
+    case CODE_FOR_mips_mulsaq_s_w_ph:
+    case CODE_FOR_mips_dpaq_sa_l_w:
+    case CODE_FOR_mips_dpsq_sa_l_w:
+    case CODE_FOR_mips_maq_s_w_phl:
+    case CODE_FOR_mips_maq_s_w_phr:
+    case CODE_FOR_mips_maq_sa_w_phl:
+    case CODE_FOR_mips_maq_sa_w_phr:
+
+    case CODE_FOR_mips_dpa_w_ph:
+    case CODE_FOR_mips_dps_w_ph:
+    case CODE_FOR_mips_mulsa_w_ph:
+    case CODE_FOR_mips_dpax_w_ph:
+    case CODE_FOR_mips_dpsx_w_ph:
+    case CODE_FOR_mips_dpaqx_s_w_ph:
+    case CODE_FOR_mips_dpaqx_sa_w_ph:
+    case CODE_FOR_mips_dpsqx_s_w_ph:
+    case CODE_FOR_mips_dpsqx_sa_w_ph:
       /* Force the operands which correspond to the same in-out register
 	  to have the same pseudo assigned to them.  If the input operand
 	  is not REG, create one for it.  */
diff --git a/gcc/testsuite/gcc.target/mips/mac-zero-reload.c b/gcc/testsuite/gcc.target/mips/mac-zero-reload.c
new file mode 100644
index 0000000..a70dfb5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/mac-zero-reload.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-fno-unroll-loops -mgp32 -mdspr2" } */
+/* { dg-skip-if "code quality test" { *-*-* } { "-O0" } { "" } } */
+/* { dg-final { scan-assembler-not "\tmflo\t" } } */
+/* { dg-final { scan-assembler-not "\tmfhi\t" } } */
+/* { dg-final { scan-assembler-not "\tmtlo\t" } } */
+/* { dg-final { scan-assembler-not "\tmthi\t" } } */
+
+typedef short v2i16 __attribute__ ((vector_size(4)));
+
+extern v2i16 ps32Ptrl[4096];
+
+extern int sink[4096];
+
+int main(void)
+{
+  v2i16 v2i16_h0;
+  long long   s64Acc;
+
+  for (int i = 0; i < 4; ++i)
+    {
+      v2i16_h0 = ps32Ptrl[i];
+
+      s64Acc = 0;
+
+      s64Acc = __builtin_mips_dpa_w_ph(s64Acc, v2i16_h0, v2i16_h0);
+
+      sink[i] = __builtin_mips_extr_rs_w(s64Acc, 0);
+    }
+
+  return 0;
+}
-- 
2.7.4

Re: [PATCH] [MIPS] Remove unnecessary moves around DSP multiply-accumulate instructions

[Jeff Law]

On Thu, 2020-02-06 at 14:05 +0100, Mihailo Stojanovic wrote:
> Unnecessary moves around dpadd and dpsub are caused by different pseudos
> being assigned to the input-output operands which correspond to the same
> register.
> 
> Just like for the MSA multiply-accumulate instructions, this forces the
> same pseudo to the input-output operands,
> which removes unnecesary moves.
> 
> Tested on mips-mti-linux-gnu.
> 
> gcc/ChangeLog:
> 
>         * gcc/config/mips/mips.c (mips_expand_builtin_insn): Operands of
>         DSP multiply-accumulate instructions which correspond to the
>         same input-output register now have the same pseudo asigned to
>         them.
> 
> gcc/testsuite/ChangeLog:
> 
>         * gcc/testsuite/gcc.target/mips/mac-zero-reload.c: New test.
Affects just MIPS, so OK even though we're in stage4.

jeff
>