[llvm] [RISCV][GlobalISel] Select G_FRAME_INDEX (PR #68254)

[Nitin John Raj via llvm-commits]

https://github.com/nitinjohnraj created https://github.com/llvm/llvm-project/pull/68254

This patch is a bandage to get G_FRAME_INDEX working. We could import the SelectionDAG patterns for the ComplexPattern FrameAddrRegImm, and perhaps we will do that in the future. For now we just select it as an addition with 0.

>From b27d7318888e7410055da6fce91f3c3495e509ea Mon Sep 17 00:00:00 2001
From: Nitin John Raj <nitin.raj at sifive.com>
Date: Tue, 26 Sep 2023 13:16:46 -0700
Subject: [PATCH 1/2] [RISCV][GlobalISel] Legalize G_FRAME_INDEX

---
 llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
index f12e868e74264f6..4479bccfd45e396 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
@@ -169,6 +169,8 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
 
   getActionDefinitionsBuilder(G_ABS).lower();
 
+  getActionDefinitionsBuilder(G_FRAME_INDEX).legalFor({p0});
+
   getLegacyLegalizerInfo().computeTables();
 }
 

>From a6843c54d112b693efa2a7c0d68a5dc669586d6d Mon Sep 17 00:00:00 2001
From: Nitin John Raj <nitin.raj at sifive.com>
Date: Tue, 3 Oct 2023 09:40:22 -0700
Subject: [PATCH 2/2] temp

---
 .../RISCV/GISel/RISCVInstructionSelector.cpp  | 10 ++++++
 .../RISCV/GISel/RISCVRegisterBankInfo.cpp     |  1 +
 .../instruction-select/frame-index-rv32.mir   | 32 +++++++++++++++++++
 .../instruction-select/frame-index-rv64.mir   | 32 +++++++++++++++++++
 4 files changed, 75 insertions(+)
 create mode 100644 llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv32.mir
 create mode 100644 llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv64.mir

diff --git a/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp b/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
index 4f97a0d84f686f9..99bcaf7d7977c49 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp
@@ -239,6 +239,16 @@ bool RISCVInstructionSelector::select(MachineInstr &MI) {
   }
   case TargetOpcode::G_SEXT_INREG:
     return selectSExtInreg(MI, MIB);
+  case TargetOpcode::G_FRAME_INDEX: {
+    Register DstReg = MI.getOperand(0).getReg();
+
+    if (!MRI.getType(DstReg).isPointer())
+      return false;
+
+    MI.setDesc(TII.get(RISCV::ADDI));
+    MI.addOperand(MachineOperand::CreateImm(0));
+    return constrainSelectedInstRegOperands(MI, TII, TRI, RBI);
+  }
   default:
     return false;
   }
diff --git a/llvm/lib/Target/RISCV/GISel/RISCVRegisterBankInfo.cpp b/llvm/lib/Target/RISCV/GISel/RISCVRegisterBankInfo.cpp
index 63686bd4bdbc3ae..59aebc7960bc3dc 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVRegisterBankInfo.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVRegisterBankInfo.cpp
@@ -127,6 +127,7 @@ RISCVRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   case TargetOpcode::G_STORE:
     break;
   case TargetOpcode::G_CONSTANT:
+  case TargetOpcode::G_FRAME_INDEX:
   case TargetOpcode::G_GLOBAL_VALUE:
   case TargetOpcode::G_BRCOND:
     OperandsMapping = getOperandsMapping({GPRValueMapping, nullptr});
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv32.mir b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv32.mir
new file mode 100644
index 000000000000000..20747bd1876180c
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv32.mir
@@ -0,0 +1,32 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -run-pass=instruction-select %s -o - \
+# RUN: | FileCheck %s
+--- |
+  define ptr @frame_index() {
+  entry:
+    %x = alloca i32, align 4
+    ret ptr %x
+  }
+
+...
+---
+name:            frame_index
+legalized:       true
+regBankSelected: true
+registers:
+  - { id: 0, class: gprb, preferred-register: '' }
+stack:
+  - { id: 0, name: x, type: default, offset: 0, size: 4, alignment: 4,
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body:             |
+  bb.1.entry:
+    ; CHECK-LABEL: name: frame_index
+    ; CHECK: [[ADDI:%[0-9]+]]:gpr = ADDI %stack.0.x, 0
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(p0) = G_FRAME_INDEX %stack.0.x
+    $x10 = COPY %0(p0)
+    PseudoRET implicit $x10
+
+...
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv64.mir b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv64.mir
new file mode 100644
index 000000000000000..dc265bda0a68894
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/instruction-select/frame-index-rv64.mir
@@ -0,0 +1,32 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv64 -run-pass=instruction-select %s -o - \
+# RUN: | FileCheck %s
+--- |
+  define ptr @frame_index() {
+  entry:
+    %x = alloca i32, align 4
+    ret ptr %x
+  }
+
+...
+---
+name:            frame_index
+legalized:       true
+regBankSelected: true
+registers:
+  - { id: 0, class: gprb, preferred-register: '' }
+stack:
+  - { id: 0, name: x, type: default, offset: 0, size: 4, alignment: 4,
+      stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body:             |
+  bb.1.entry:
+    ; CHECK-LABEL: name: frame_index
+    ; CHECK: [[ADDI:%[0-9]+]]:gpr = ADDI %stack.0.x, 0
+    ; CHECK-NEXT: $x10 = COPY [[ADDI]]
+    ; CHECK-NEXT: PseudoRET implicit $x10
+    %0:gprb(p0) = G_FRAME_INDEX %stack.0.x
+    $x10 = COPY %0(p0)
+    PseudoRET implicit $x10
+
+...