From e89ef1cdf4186e20469043167079dc95f14ce666 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sun, 16 Aug 2026 20:23:21 +0800
Subject: [RISCV][GlobalISel] Generate high multiply selections

---
 backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc | 36 ++++++++++++++++++++++
 1 file changed, 36 insertions(+)

(limited to 'backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc')

diff --git a/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc b/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
index 0413007..e096993 100644
--- a/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
+++ b/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
@@ -217,6 +217,42 @@ selection_rules:
         - opcode: MUL
           root: true
           operands: [{ operand: 0 }, { operand: 1 }, { operand: 2 }]
+  -
+    id: select_g_smulh_register
+    priority: 100
+    match:
+      opcode: G_SMULH
+      result_type: { kind: scalar, bits: 64 }
+      operand_types:
+        - { index: 1, kind: scalar, bits: 64 }
+        - { index: 2, kind: scalar, bits: 64 }
+      operand_banks:
+        - { index: 0, bank: GPR }
+        - { index: 1, bank: GPR }
+        - { index: 2, bank: GPR }
+    apply:
+      instructions:
+        - opcode: MULH
+          root: true
+          operands: [{ operand: 0 }, { operand: 1 }, { operand: 2 }]
+  -
+    id: select_g_umulh_register
+    priority: 100
+    match:
+      opcode: G_UMULH
+      result_type: { kind: scalar, bits: 64 }
+      operand_types:
+        - { index: 1, kind: scalar, bits: 64 }
+        - { index: 2, kind: scalar, bits: 64 }
+      operand_banks:
+        - { index: 0, bank: GPR }
+        - { index: 1, bank: GPR }
+        - { index: 2, bank: GPR }
+    apply:
+      instructions:
+        - opcode: MULHU
+          root: true
+          operands: [{ operand: 0 }, { operand: 1 }, { operand: 2 }]
   -
     id: select_g_sdiv_register
     priority: 100
-- 
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