From 46361bea1f4b1483780d91e4d60d6f44cf0b5706 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sun, 16 Aug 2026 18:11:01 +0800
Subject: [RISCV][GlobalISel] Generate pointer arithmetic selections

---
 .../RISCV/GISel/RISCVInstructionSelector.cpp       |  9 ---
 backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc | 84 ++++++++++++++++++++++
 2 files changed, 84 insertions(+), 9 deletions(-)

(limited to 'backend')

diff --git a/backend/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp b/backend/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
index edf0b40..08e9f6c 100644
--- a/backend/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
+++ b/backend/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
@@ -203,8 +203,6 @@ public:
     case GenericOpcode::G_SHL:
     case GenericOpcode::G_LSHR:
     case GenericOpcode::G_ASHR:
-    case GenericOpcode::G_PTR_ADD:
-    case GenericOpcode::G_PTRMASK:
     case GenericOpcode::G_CONSTANT:
       if (!Integer())
         return makeUnexpected(ErrorCode::Unsupported,
@@ -311,9 +309,6 @@ public:
     const GenericOpcode Generic = static_cast<GenericOpcode>(Instruction.opcode().value());
     const std::optional<LowLevelType> Type = resultType(Function, Instruction);
 
-    const auto SelectDirect = [&Instruction](InstructionOpcode Selected) {
-      return Instruction.setOpcode(instructionOpcode(Selected));
-    };
     switch (Generic) {
     case GenericOpcode::G_ADD:
       return selectIntegerBinary(Instruction, Function, Type, InstructionOpcode::ADD,
@@ -379,10 +374,6 @@ public:
       return selectNormalizedIntegerBinary(
           Instruction, Function, Target, Type, InstructionOpcode::SRA, InstructionOpcode::SRAW,
           true, false, InstructionOpcode::SRAI, InstructionOpcode::SRAIW, false, 6, 5);
-    case GenericOpcode::G_PTR_ADD:
-      return SelectDirect(InstructionOpcode::ADD);
-    case GenericOpcode::G_PTRMASK:
-      return SelectDirect(InstructionOpcode::AND);
     case GenericOpcode::G_LOAD:
       return selectLoad(Instruction, Function, Type);
     case GenericOpcode::G_SEXTLOAD:
diff --git a/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc b/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
index d8b0a42..9e32842 100644
--- a/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
+++ b/backend/lib/Target/RISCV/RISCVGISelInteger.rccdesc
@@ -1,4 +1,88 @@
 selection_rules:
+  -
+    id: select_g_ptr_add_immediate
+    priority: 400
+    match:
+      opcode: G_PTR_ADD
+      result_type: { kind: pointer, bits: 64 }
+      operand_types:
+        - { index: 1, kind: pointer, bits: 64 }
+        - { index: 2, kind: scalar, bits: 64 }
+      operand_banks:
+        - { index: 0, bank: GPR }
+        - { index: 1, bank: GPR }
+      operand_def_constants:
+        - index: 2
+          ranges: [{ min: -2048, max: 2047 }]
+    apply:
+      instructions:
+        - opcode: ADDI
+          root: true
+          operands:
+            - { operand: 0 }
+            - { operand: 1 }
+            - { captured_immediate: 2 }
+      erase_operand_definitions: [2]
+  -
+    id: select_g_ptrmask_immediate
+    priority: 400
+    match:
+      opcode: G_PTRMASK
+      result_type: { kind: pointer, bits: 64 }
+      operand_types:
+        - { index: 1, kind: pointer, bits: 64 }
+        - { index: 2, kind: scalar, bits: 64 }
+      operand_banks:
+        - { index: 0, bank: GPR }
+        - { index: 1, bank: GPR }
+      operand_def_constants:
+        - index: 2
+          ranges: [{ min: -2048, max: 2047 }]
+    apply:
+      instructions:
+        - opcode: ANDI
+          root: true
+          operands:
+            - { operand: 0 }
+            - { operand: 1 }
+            - { captured_immediate: 2 }
+      erase_operand_definitions: [2]
+  -
+    id: select_g_ptr_add_register
+    priority: 100
+    match:
+      opcode: G_PTR_ADD
+      result_type: { kind: pointer, bits: 64 }
+      operand_types:
+        - { index: 1, kind: pointer, 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: ADD
+          root: true
+          operands: [{ operand: 0 }, { operand: 1 }, { operand: 2 }]
+  -
+    id: select_g_ptrmask_register
+    priority: 100
+    match:
+      opcode: G_PTRMASK
+      result_type: { kind: pointer, bits: 64 }
+      operand_types:
+        - { index: 1, kind: pointer, 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: AND
+          root: true
+          operands: [{ operand: 0 }, { operand: 1 }, { operand: 2 }]
   -
     id: select_g_sllw
     priority: 100
-- 
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