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[RISCV] Peephole optimisation for load/store of global values or constant addresses 

(load (add base, off), 0) -> (load base, off)
(store val, (add base, off)) -> (store val, base, off)

This is similar to an equivalent peephole optimisation in PPCISelDAGToDAG.

llvm-svn: 327831
This commit is contained in:
Alex Bradbury 2018-03-19 11:54:28 +00:00
parent fa0217276a
commit 0171a9f4ec
7 changed files with 131 additions and 67 deletions
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95
llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
View File

@ -42,6 +42,8 @@ public:
return SelectionDAGISel::runOnMachineFunction(MF);
}
void PostprocessISelDAG() override;
void Select(SDNode *Node) override;
bool SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
@ -51,9 +53,14 @@ public:
// Include the pieces autogenerated from the target description.
#include "RISCVGenDAGISel.inc"
private:
void doPeepholeLoadStoreADDI();
};
}
void RISCVDAGToDAGISel::PostprocessISelDAG() { doPeepholeLoadStoreADDI(); }
void RISCVDAGToDAGISel::Select(SDNode *Node) {
unsigned Opcode = Node->getOpcode();
MVT XLenVT = Subtarget->getXLenVT();
@ -117,6 +124,94 @@ bool RISCVDAGToDAGISel::SelectAddrFI(SDValue Addr, SDValue &Base) {
return false;
}
// Merge an ADDI into the offset of a load/store instruction where possible.
// (load (add base, off), 0) -> (load base, off)
// (store val, (add base, off)) -> (store val, base, off)
void RISCVDAGToDAGISel::doPeepholeLoadStoreADDI() {
SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
++Position;
while (Position != CurDAG->allnodes_begin()) {
SDNode *N = &*--Position;
// Skip dead nodes and any non-machine opcodes.
if (N->use_empty() || !N->isMachineOpcode())
continue;
int OffsetOpIdx;
int BaseOpIdx;
// Only attempt this optimisation for I-type loads and S-type stores.
switch (N->getMachineOpcode()) {
default:
continue;
case RISCV::LB:
case RISCV::LH:
case RISCV::LW:
case RISCV::LBU:
case RISCV::LHU:
case RISCV::LWU:
case RISCV::LD:
case RISCV::FLW:
case RISCV::FLD:
BaseOpIdx = 0;
OffsetOpIdx = 1;
break;
case RISCV::SB:
case RISCV::SH:
case RISCV::SW:
case RISCV::SD:
case RISCV::FSW:
case RISCV::FSD:
BaseOpIdx = 1;
OffsetOpIdx = 2;
break;
}
// Currently, the load/store offset must be 0 to be considered for this
// peephole optimisation.
if (!isa<ConstantSDNode>(N->getOperand(OffsetOpIdx)) ||
N->getConstantOperandVal(OffsetOpIdx) != 0)
continue;
SDValue Base = N->getOperand(BaseOpIdx);
// If the base is an ADDI, we can merge it in to the load/store.
if (!Base.isMachineOpcode() || Base.getMachineOpcode() != RISCV::ADDI)
continue;
SDValue ImmOperand = Base.getOperand(1);
if (auto Const = dyn_cast<ConstantSDNode>(ImmOperand)) {
ImmOperand = CurDAG->getTargetConstant(
Const->getSExtValue(), SDLoc(ImmOperand), ImmOperand.getValueType());
} else if (auto GA = dyn_cast<GlobalAddressSDNode>(ImmOperand)) {
ImmOperand = CurDAG->getTargetGlobalAddress(
GA->getGlobal(), SDLoc(ImmOperand), ImmOperand.getValueType(),
GA->getOffset(), GA->getTargetFlags());
} else {
continue;
}
DEBUG(dbgs() << "Folding add-immediate into mem-op:\nBase: ");
DEBUG(Base->dump(CurDAG));
DEBUG(dbgs() << "\nN: ");
DEBUG(N->dump(CurDAG));
DEBUG(dbgs() << "\n");
// Modify the offset operand of the load/store.
if (BaseOpIdx == 0) // Load
CurDAG->UpdateNodeOperands(N, Base.getOperand(0), ImmOperand,
N->getOperand(2));
else // Store
CurDAG->UpdateNodeOperands(N, N->getOperand(0), Base.getOperand(0),
ImmOperand, N->getOperand(3));
// The add-immediate may now be dead, in which case remove it.
if (Base.getNode()->use_empty())
CurDAG->RemoveDeadNode(Base.getNode());
}
}
// This pass converts a legalized DAG into a RISCV-specific DAG, ready
// for instruction scheduling.
FunctionPass *llvm::createRISCVISelDag(RISCVTargetMachine &TM) {

11
llvm/test/CodeGen/RISCV/blockaddress.ll
View File

@ -9,12 +9,11 @@ define void @test_blockaddress() nounwind {
; RV32I: # %bb.0:
; RV32I-NEXT: addi sp, sp, -16
; RV32I-NEXT: sw ra, 12(sp)
; RV32I-NEXT: lui a0, %hi(addr)
; RV32I-NEXT: addi a0, a0, %lo(addr)
; RV32I-NEXT: lui a1, %hi(.Ltmp0)
; RV32I-NEXT: addi a1, a1, %lo(.Ltmp0)
; RV32I-NEXT: sw a1, 0(a0)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lui a0, %hi(.Ltmp0)
; RV32I-NEXT: addi a0, a0, %lo(.Ltmp0)
; RV32I-NEXT: lui a1, %hi(addr)
; RV32I-NEXT: sw a0, %lo(addr)(a1)
; RV32I-NEXT: lw a0, %lo(addr)(a1)
; RV32I-NEXT: jr a0
; RV32I-NEXT: .Ltmp0: # Block address taken
; RV32I-NEXT: .LBB0_1: # %block

12
llvm/test/CodeGen/RISCV/byval.ll
View File

@ -23,20 +23,16 @@ define void @caller() nounwind {
; RV32I-NEXT: addi sp, sp, -32
; RV32I-NEXT: sw ra, 28(sp)
; RV32I-NEXT: lui a0, %hi(foo+12)
; RV32I-NEXT: addi a0, a0, %lo(foo+12)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(foo+12)(a0)
; RV32I-NEXT: sw a0, 24(sp)
; RV32I-NEXT: lui a0, %hi(foo+8)
; RV32I-NEXT: addi a0, a0, %lo(foo+8)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(foo+8)(a0)
; RV32I-NEXT: sw a0, 20(sp)
; RV32I-NEXT: lui a0, %hi(foo+4)
; RV32I-NEXT: addi a0, a0, %lo(foo+4)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(foo+4)(a0)
; RV32I-NEXT: sw a0, 16(sp)
; RV32I-NEXT: lui a0, %hi(foo)
; RV32I-NEXT: addi a0, a0, %lo(foo)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(foo)(a0)
; RV32I-NEXT: sw a0, 12(sp)
; RV32I-NEXT: lui a0, %hi(callee)
; RV32I-NEXT: addi a1, a0, %lo(callee)

48
llvm/test/CodeGen/RISCV/fp128.ll
View File

@ -14,36 +14,28 @@ define i32 @test_load_and_cmp() nounwind {
; RV32I-NEXT: addi sp, sp, -48
; RV32I-NEXT: sw ra, 44(sp)
; RV32I-NEXT: lui a0, %hi(y+12)
; RV32I-NEXT: addi a0, a0, %lo(y+12)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+12)(a0)
; RV32I-NEXT: sw a0, 20(sp)
; RV32I-NEXT: lui a0, %hi(y+8)
; RV32I-NEXT: addi a0, a0, %lo(y+8)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+8)(a0)
; RV32I-NEXT: sw a0, 16(sp)
; RV32I-NEXT: lui a0, %hi(y+4)
; RV32I-NEXT: addi a0, a0, %lo(y+4)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+4)(a0)
; RV32I-NEXT: sw a0, 12(sp)
; RV32I-NEXT: lui a0, %hi(y)
; RV32I-NEXT: addi a0, a0, %lo(y)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y)(a0)
; RV32I-NEXT: sw a0, 8(sp)
; RV32I-NEXT: lui a0, %hi(x+12)
; RV32I-NEXT: addi a0, a0, %lo(x+12)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+12)(a0)
; RV32I-NEXT: sw a0, 36(sp)
; RV32I-NEXT: lui a0, %hi(x+8)
; RV32I-NEXT: addi a0, a0, %lo(x+8)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+8)(a0)
; RV32I-NEXT: sw a0, 32(sp)
; RV32I-NEXT: lui a0, %hi(x+4)
; RV32I-NEXT: addi a0, a0, %lo(x+4)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+4)(a0)
; RV32I-NEXT: sw a0, 28(sp)
; RV32I-NEXT: lui a0, %hi(x)
; RV32I-NEXT: addi a0, a0, %lo(x)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x)(a0)
; RV32I-NEXT: sw a0, 24(sp)
; RV32I-NEXT: lui a0, %hi(__netf2)
; RV32I-NEXT: addi a2, a0, %lo(__netf2)
@ -68,36 +60,28 @@ define i32 @test_add_and_fptosi() nounwind {
; RV32I-NEXT: addi sp, sp, -80
; RV32I-NEXT: sw ra, 76(sp)
; RV32I-NEXT: lui a0, %hi(y+12)
; RV32I-NEXT: addi a0, a0, %lo(y+12)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+12)(a0)
; RV32I-NEXT: sw a0, 36(sp)
; RV32I-NEXT: lui a0, %hi(y+8)
; RV32I-NEXT: addi a0, a0, %lo(y+8)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+8)(a0)
; RV32I-NEXT: sw a0, 32(sp)
; RV32I-NEXT: lui a0, %hi(y+4)
; RV32I-NEXT: addi a0, a0, %lo(y+4)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y+4)(a0)
; RV32I-NEXT: sw a0, 28(sp)
; RV32I-NEXT: lui a0, %hi(y)
; RV32I-NEXT: addi a0, a0, %lo(y)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(y)(a0)
; RV32I-NEXT: sw a0, 24(sp)
; RV32I-NEXT: lui a0, %hi(x+12)
; RV32I-NEXT: addi a0, a0, %lo(x+12)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+12)(a0)
; RV32I-NEXT: sw a0, 52(sp)
; RV32I-NEXT: lui a0, %hi(x+8)
; RV32I-NEXT: addi a0, a0, %lo(x+8)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+8)(a0)
; RV32I-NEXT: sw a0, 48(sp)
; RV32I-NEXT: lui a0, %hi(x+4)
; RV32I-NEXT: addi a0, a0, %lo(x+4)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x+4)(a0)
; RV32I-NEXT: sw a0, 44(sp)
; RV32I-NEXT: lui a0, %hi(x)
; RV32I-NEXT: addi a0, a0, %lo(x)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(x)(a0)
; RV32I-NEXT: sw a0, 40(sp)
; RV32I-NEXT: lui a0, %hi(__addtf3)
; RV32I-NEXT: addi a3, a0, %lo(__addtf3)

3
llvm/test/CodeGen/RISCV/inline-asm.ll
View File

@ -8,8 +8,7 @@ define i32 @constraint_r(i32 %a) {
; RV32I-LABEL: constraint_r:
; RV32I: # %bb.0:
; RV32I-NEXT: lui a1, %hi(gi)
; RV32I-NEXT: addi a1, a1, %lo(gi)
; RV32I-NEXT: lw a1, 0(a1)
; RV32I-NEXT: lw a1, %lo(gi)(a1)
; RV32I-NEXT: #APP
; RV32I-NEXT: add a0, a0, a1
; RV32I-NEXT: #NO_APP

21
llvm/test/CodeGen/RISCV/mem.ll
View File

@ -163,17 +163,14 @@ define i16 @load_sext_zext_anyext_i1_i16(i1 *%a) nounwind {
@G = global i32 0
define i32 @lw_sw_global(i32 %a) nounwind {
; TODO: the addi should be folded in to the lw/sw operations
; RV32I-LABEL: lw_sw_global:
; RV32I: # %bb.0:
; RV32I-NEXT: lui a1, %hi(G)
; RV32I-NEXT: addi a2, a1, %lo(G)
; RV32I-NEXT: lw a1, 0(a2)
; RV32I-NEXT: sw a0, 0(a2)
; RV32I-NEXT: lui a2, %hi(G)
; RV32I-NEXT: lw a1, %lo(G)(a2)
; RV32I-NEXT: sw a0, %lo(G)(a2)
; RV32I-NEXT: lui a2, %hi(G+36)
; RV32I-NEXT: addi a2, a2, %lo(G+36)
; RV32I-NEXT: lw a3, 0(a2)
; RV32I-NEXT: sw a0, 0(a2)
; RV32I-NEXT: lw a3, %lo(G+36)(a2)
; RV32I-NEXT: sw a0, %lo(G+36)(a2)
; RV32I-NEXT: mv a0, a1
; RV32I-NEXT: ret
%1 = load volatile i32, i32* @G
@ -186,13 +183,11 @@ define i32 @lw_sw_global(i32 %a) nounwind {
; Ensure that 1 is added to the high 20 bits if bit 11 of the low part is 1
define i32 @lw_sw_constant(i32 %a) nounwind {
; TODO: the addi should be folded in to the lw/sw
; RV32I-LABEL: lw_sw_constant:
; RV32I: # %bb.0:
; RV32I-NEXT: lui a1, 912092
; RV32I-NEXT: addi a2, a1, -273
; RV32I-NEXT: lw a1, 0(a2)
; RV32I-NEXT: sw a0, 0(a2)
; RV32I-NEXT: lui a2, 912092
; RV32I-NEXT: lw a1, -273(a2)
; RV32I-NEXT: sw a0, -273(a2)
; RV32I-NEXT: mv a0, a1
; RV32I-NEXT: ret
%1 = inttoptr i32 3735928559 to i32*

8
llvm/test/CodeGen/RISCV/wide-mem.ll
View File

@ -17,17 +17,13 @@ define i64 @load_i64(i64 *%a) nounwind {
@val64 = local_unnamed_addr global i64 2863311530, align 8
; TODO: codegen on this should be improved. It shouldn't be necessary to
; generate two addi
define i64 @load_i64_global() nounwind {
; RV32I-LABEL: load_i64_global:
; RV32I: # %bb.0:
; RV32I-NEXT: lui a0, %hi(val64)
; RV32I-NEXT: addi a0, a0, %lo(val64)
; RV32I-NEXT: lw a0, 0(a0)
; RV32I-NEXT: lw a0, %lo(val64)(a0)
; RV32I-NEXT: lui a1, %hi(val64+4)
; RV32I-NEXT: addi a1, a1, %lo(val64+4)
; RV32I-NEXT: lw a1, 0(a1)
; RV32I-NEXT: lw a1, %lo(val64+4)(a1)
; RV32I-NEXT: ret
%1 = load i64, i64* @val64
ret i64 %1