[RISCV] Teach RISCVMergeBaseOffset to handle BlockAddress

[wangpc]

Summary

We can get BlockAddress in user code via Labels as Values so
we should be able to merge the access to BlockAddress.

[wangpc]

Ping.

[craig.topper]

LGTM

llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp

if (Hi.getOpcode() != RISCV::LUI && Hi.getOpcode() != RISCV::AUIPC)
     return false;
 
   const MachineOperand &HiOp1 = Hi.getOperand(1);
   unsigned ExpectedFlags =
       Hi.getOpcode() == RISCV::AUIPC ? RISCVII::MO_PCREL_HI : RISCVII::MO_HI;
   if (HiOp1.getTargetFlags() != ExpectedFlags)
     return false;
 
-  if (!(HiOp1.isGlobal() || HiOp1.isCPI()) || HiOp1.getOffset() != 0)
+  if (!(HiOp1.isGlobal() || HiOp1.isCPI() || HiOp1.isBlockAddress()) ||
+      HiOp1.getOffset() != 0)
     return false;
 
   Register HiDestReg = Hi.getOperand(0).getReg();
   if (!MRI->hasOneUse(HiDestReg))
     return false;
 
   Lo = &*MRI->use_instr_begin(HiDestReg);
   if (Lo->getOpcode() != RISCV::ADDI)
     return false;
 
   const MachineOperand &LoOp2 = Lo->getOperand(2);
   if (Hi.getOpcode() == RISCV::LUI) {
     if (LoOp2.getTargetFlags() != RISCVII::MO_LO ||
-        !(LoOp2.isGlobal() || LoOp2.isCPI()) || LoOp2.getOffset() != 0)
+        !(LoOp2.isGlobal() || LoOp2.isCPI() || LoOp2.isBlockAddress()) ||
+        LoOp2.getOffset() != 0)
       return false;
   } else {
     assert(Hi.getOpcode() == RISCV::AUIPC);
     if (LoOp2.getTargetFlags() != RISCVII::MO_PCREL_LO ||
         LoOp2.getType() != MachineOperand::MO_MCSymbol)
       return false;
   }
 
   if (HiOp1.isGlobal()) {
     LLVM_DEBUG(dbgs() << "  Found lowered global address: "
                       << *HiOp1.getGlobal() << "\n");
-  } else {
-    assert(HiOp1.isCPI());
+  } else if (HiOp1.isBlockAddress()) {
+    LLVM_DEBUG(dbgs() << "  Found lowered basic address: "
+                      << *HiOp1.getBlockAddress() << "\n");
+  } else if (HiOp1.isCPI()) {
     LLVM_DEBUG(dbgs() << "  Found lowered constant pool: " << HiOp1.getIndex()
                       << "\n");
   }
 
   return true;
 }
 
 // Update the offset in Hi and Lo instructions.

llvm/test/CodeGen/RISCV/fold-addi-loadstore.ll

 ; RV32I-NEXT:    ret
 ;
 ; RV32I-MEDIUM-LABEL: load_ba_1:
 ; RV32I-MEDIUM:       # %bb.0: # %entry
 ; RV32I-MEDIUM-NEXT:  .Ltmp0: # Block address taken
 ; RV32I-MEDIUM-NEXT:  # %bb.1: # %label
 ; RV32I-MEDIUM-NEXT:  .Lpcrel_hi12:
 ; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp0)
-; RV32I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi12)
-; RV32I-MEDIUM-NEXT:    lw a0, 0(a0)
+; RV32I-MEDIUM-NEXT:    lw a0, %pcrel_lo(.Lpcrel_hi12)(a0)
 ; RV32I-MEDIUM-NEXT:    ret
 ;
 ; RV64I-LABEL: load_ba_1:
 ; RV64I:       # %bb.0: # %entry
 ; RV64I-NEXT:  .Ltmp0: # Block address taken
 ; RV64I-NEXT:  # %bb.1: # %label
 ; RV64I-NEXT:    lui a0, %hi(.Ltmp0)
 ; RV64I-NEXT:    ld a0, %lo(.Ltmp0)(a0)
 ; RV64I-NEXT:    ret
 ;
 ; RV64I-MEDIUM-LABEL: load_ba_1:
 ; RV64I-MEDIUM:       # %bb.0: # %entry
 ; RV64I-MEDIUM-NEXT:  .Ltmp0: # Block address taken
 ; RV64I-MEDIUM-NEXT:  # %bb.1: # %label
 ; RV64I-MEDIUM-NEXT:  .Lpcrel_hi12:
 ; RV64I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp0)
-; RV64I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi12)
-; RV64I-MEDIUM-NEXT:    ld a0, 0(a0)
+; RV64I-MEDIUM-NEXT:    ld a0, %pcrel_lo(.Lpcrel_hi12)(a0)
 ; RV64I-MEDIUM-NEXT:    ret
 entry:
   br label %label
 label:
   %0 = load ptr, ptr blockaddress(@load_ba_1, %label)
   ret ptr %0
 }
 
 define dso_local ptr @load_ba_2() nounwind {
 ; RV32I-LABEL: load_ba_2:
 ; RV32I:       # %bb.0: # %entry
 ; RV32I-NEXT:  .Ltmp1: # Block address taken
 ; RV32I-NEXT:  # %bb.1: # %label
-; RV32I-NEXT:    lui a0, %hi(.Ltmp1)
-; RV32I-NEXT:    addi a0, a0, %lo(.Ltmp1)
-; RV32I-NEXT:    lw a0, 8(a0)
+; RV32I-NEXT:    lui a0, %hi(.Ltmp1+8)
+; RV32I-NEXT:    lw a0, %lo(.Ltmp1+8)(a0)
 ; RV32I-NEXT:    ret
 ;
 ; RV32I-MEDIUM-LABEL: load_ba_2:
 ; RV32I-MEDIUM:       # %bb.0: # %entry
 ; RV32I-MEDIUM-NEXT:  .Ltmp1: # Block address taken
 ; RV32I-MEDIUM-NEXT:  # %bb.1: # %label
 ; RV32I-MEDIUM-NEXT:  .Lpcrel_hi13:
-; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp1)
-; RV32I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi13)
-; RV32I-MEDIUM-NEXT:    lw a0, 8(a0)
+; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp1+8)
+; RV32I-MEDIUM-NEXT:    lw a0, %pcrel_lo(.Lpcrel_hi13)(a0)
 ; RV32I-MEDIUM-NEXT:    ret
 ;
 ; RV64I-LABEL: load_ba_2:
 ; RV64I:       # %bb.0: # %entry
 ; RV64I-NEXT:  .Ltmp1: # Block address taken
 ; RV64I-NEXT:  # %bb.1: # %label
-; RV64I-NEXT:    lui a0, %hi(.Ltmp1)
-; RV64I-NEXT:    addi a0, a0, %lo(.Ltmp1)
-; RV64I-NEXT:    ld a0, 8(a0)
+; RV64I-NEXT:    lui a0, %hi(.Ltmp1+8)
+; RV64I-NEXT:    ld a0, %lo(.Ltmp1+8)(a0)
 ; RV64I-NEXT:    ret
 ;
 ; RV64I-MEDIUM-LABEL: load_ba_2:
 ; RV64I-MEDIUM:       # %bb.0: # %entry
 ; RV64I-MEDIUM-NEXT:  .Ltmp1: # Block address taken
 ; RV64I-MEDIUM-NEXT:  # %bb.1: # %label
 ; RV64I-MEDIUM-NEXT:  .Lpcrel_hi13:
-; RV64I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp1)
-; RV64I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi13)
-; RV64I-MEDIUM-NEXT:    ld a0, 8(a0)
+; RV64I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(.Ltmp1+8)
+; RV64I-MEDIUM-NEXT:    ld a0, %pcrel_lo(.Lpcrel_hi13)(a0)
 ; RV64I-MEDIUM-NEXT:    ret
 entry:
   br label %label
 label:
   %0 = load ptr, ptr getelementptr inbounds (i8, ptr blockaddress(@load_ba_2, %label), i32 8)
   ret ptr %0
 }