[PATCH] D54296: [WIP, RISCV] Lower inline asm constraint A for RISC-V

[Lewis Revill via Phabricator via llvm-commits]

lewis-revill created this revision.
lewis-revill added a reviewer: asb.
Herald added subscribers: llvm-commits, jocewei, PkmX, rkruppe, the_o, brucehoult, MartinMosbeck, rogfer01, mgrang, edward-jones, zzheng, jrtc27, shiva0217, kito-cheng, niosHD, sabuasal, apazos, simoncook, johnrusso, rbar, eraman.

This allows arguments with the constraint A to be lowered to input nodes for RISC-V, which implies a memory address stored in a register.

This patch adds the minimal amount of code required to get operands with the right constraints to compile. Semantically it would be nice to be able to treat the constraint as a `C_RegisterClass` and then verify and lower the register as a memory operand.


Repository:
  rL LLVM

https://reviews.llvm.org/D54296

Files:
  lib/Target/RISCV/RISCVISelLowering.cpp
  lib/Target/RISCV/RISCVISelLowering.h
  test/CodeGen/RISCV/inline-asm.ll


Index: test/CodeGen/RISCV/inline-asm.ll
===================================================================
--- test/CodeGen/RISCV/inline-asm.ll
+++ test/CodeGen/RISCV/inline-asm.ll
@@ -87,4 +87,19 @@
   ret void
 }
 
+define void @constraint_A(i8* %a) {
+; RV32I-LABEL: constraint_A:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    sb s0, 0(a0)
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    lb s1, 0(a0)
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+  tail call void asm sideeffect "sb s0, $0", "*A"(i8* %a)
+  tail call void asm sideeffect "lb s1, $0", "*A"(i8* %a)
+  ret void
+}
+
 ; TODO: expend tests for more complex constraints, out of range immediates etc
Index: lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.h
+++ lib/Target/RISCV/RISCVISelLowering.h
@@ -63,6 +63,11 @@
   // This method returns the name of a target specific DAG node.
   const char *getTargetNodeName(unsigned Opcode) const override;
 
+  // Get the type of an inline asm constraint.
+  ConstraintType getConstraintType(StringRef Constraint) const override;
+
+  unsigned getInlineAsmMemConstraint(StringRef ConstraintCode) const override;
+
   std::pair<unsigned, const TargetRegisterClass *>
   getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                StringRef Constraint, MVT VT) const override;
Index: lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.cpp
+++ lib/Target/RISCV/RISCVISelLowering.cpp
@@ -1604,6 +1604,21 @@
   return nullptr;
 }
 
+RISCVTargetLowering::ConstraintType
+RISCVTargetLowering::getConstraintType(StringRef Constraint) const {
+  // Currently only support length 1 constraints.
+  if (Constraint.size() == 1) {
+    switch (Constraint[0]) {
+    case 'A':
+      return C_Memory;
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getConstraintType(Constraint);
+}
+
 std::pair<unsigned, const TargetRegisterClass *>
 RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                                   StringRef Constraint,
@@ -1622,6 +1637,21 @@
   return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
 }
 
+unsigned
+RISCVTargetLowering::getInlineAsmMemConstraint(StringRef ConstraintCode) const {
+  // Currently only support length 1 constraints.
+  if (ConstraintCode.size() == 1) {
+    switch (ConstraintCode[0]) {
+    case 'A':
+      return InlineAsm::Constraint_m;
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
+}
+
 void RISCVTargetLowering::LowerAsmOperandForConstraint(
     SDValue Op, std::string &Constraint, std::vector<SDValue> &Ops,
     SelectionDAG &DAG) const {


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