[PATCH] [MIPS] PR82981 - mulditi3 pattern for MIPS64R6

[Mihailo Stojanovic]

This expands the existing MIPS mulditi3 pattern by adding support for
MIPS64R6 multiplication instructions.

gcc/ChangeLog:

        * config/mips/mips.md (<u>mulditi3): Generate patterns for high
        doubleword and low doubleword result of multiplication on
        MIPS64R6.

gcc/testsuite/ChangeLog:

        * gcc.target/mips/mips64r6-ti-mult.c: New test.

---

Not sure if I should add "PR target/82981" above the ChangeLog entries,
as there was already one patch which addressed the issue, but didn't
resolve it completely.
---
 gcc/config/mips/mips.md                          | 15 ++++++++++++---
 gcc/testsuite/gcc.target/mips/mips64r6-ti-mult.c | 16 ++++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/mips/mips64r6-ti-mult.c

diff --git a/gcc/config/mips/mips.md b/gcc/config/mips/mips.md
index 4ad5c62..658f5e6 100644
--- a/gcc/config/mips/mips.md
+++ b/gcc/config/mips/mips.md
@@ -2464,9 +2464,11 @@
   [(set (match_operand:TI 0 "register_operand")
 	(mult:TI (any_extend:TI (match_operand:DI 1 "register_operand"))
 		 (any_extend:TI (match_operand:DI 2 "register_operand"))))]
-  "ISA_HAS_DMULT && !(<CODE> == ZERO_EXTEND && TARGET_FIX_VR4120)"
+  "ISA_HAS_R6DMUL
+   || (ISA_HAS_DMULT
+       && !(<CODE> == ZERO_EXTEND && TARGET_FIX_VR4120))"
 {
-  rtx hilo;
+  rtx hilo, hi, lo;
 
   if (TARGET_MIPS16)
     {
@@ -2476,9 +2478,16 @@
     }
   else if (TARGET_FIX_R4000)
     emit_insn (gen_<u>mulditi3_r4000 (operands[0], operands[1], operands[2]));
-  else
+  else if (ISA_HAS_DMULT)
     emit_insn (gen_<u>mulditi3_internal (operands[0], operands[1],
 					 operands[2]));
+  else
+    {
+      hi = mips_subword (operands[0], 1);
+      lo = mips_subword (operands[0], 0);
+      emit_insn (gen_muldi3_mul3_nohilo (lo, operands[1], operands[2]));
+      emit_insn (gen_<su>muldi3_highpart_r6 (hi, operands[1], operands[2]));
+    }
   DONE;
 })
 
diff --git a/gcc/testsuite/gcc.target/mips/mips64r6-ti-mult.c b/gcc/testsuite/gcc.target/mips/mips64r6-ti-mult.c
new file mode 100644
index 0000000..f969e76
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/mips64r6-ti-mult.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-mabi=64 -march=mips64r6" } */
+/* { dg-skip-if "code quality test" { *-*-* } { "-O0" } } */
+
+typedef unsigned __int128 u128;
+typedef unsigned long long u64;
+
+u128
+test (u64 a, u64 b)
+{
+  return (u128)a * (u128)b;
+}
+
+/* { dg-final { scan-assembler-not "__multi3" } } */
+/* { dg-final { scan-assembler "dmul" } } */
+/* { dg-final { scan-assembler "dmuhu" } } */
-- 
2.7.4