[PATCH] D126986: [RISCV] Support LUI+ADDIW in doPeepholeLoadStoreADDI.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
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This fixes an inconsistency between RV32 and RV64. Still considering
trying to do this peephole during isel, but wanted to fix the
inconsistency first.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126986

Files:
  llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
  llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll


Index: llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll
===================================================================
--- llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll
+++ llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll
@@ -319,13 +319,13 @@
 }
 
 define dso_local i32 @load_const_medium() nounwind {
-; RV32I-LABEL: load_const_two_addi:
+; RV32I-LABEL: load_const_medium:
 ; RV32I:       # %bb.0: # %entry
 ; RV32I-NEXT:    lui a0, 1
 ; RV32I-NEXT:    lw a0, -16(a0)
 ; RV32I-NEXT:    ret
 ;
-; RV64I-LABEL: load_const_two_addi:
+; RV64I-LABEL: load_const_medium:
 ; RV64I:       # %bb.0: # %entry
 ; RV64I-NEXT:    lui a0, 1
 ; RV64I-NEXT:    lw a0, -16(a0)
Index: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -2233,9 +2233,22 @@
   if (!Base.isMachineOpcode())
     return false;
 
-  // If the base is an ADDI, we can merge it in to the load/store.
-  if (Base.getMachineOpcode() != RISCV::ADDI)
-    return false;
+  if (Base.getMachineOpcode() == RISCV::ADDI) {
+    // If the base is an ADDI, we can merge it in to the load/store.
+  } else if (Base.getMachineOpcode() == RISCV::ADDIW &&
+             isa<ConstantSDNode>(Base.getOperand(1)) &&
+             Base.getOperand(0).isMachineOpcode() &&
+             Base.getOperand(0).getMachineOpcode() == RISCV::LUI &&
+             isa<ConstantSDNode>(Base.getOperand(0).getOperand(0))) {
+    // ADDIW can be merged if it's part of LUI+ADDIW and W doesn't change the
+    // value.
+    int64_t Offset =
+      SignExtend64<32>(Base.getOperand(0).getConstantOperandVal(0) << 12);
+    Offset += cast<ConstantSDNode>(Base.getOperand(1))->getSExtValue();
+    if (!isInt<32>(Offset))
+      return false;
+  } else
+   return false;
 
   SDValue ImmOperand = Base.getOperand(1);
   uint64_t Offset2 = N->getConstantOperandVal(OffsetOpIdx);


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