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[RISCV][GISel] Implement canLowerReturn. (llvm#105465)
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This allows us to handle return values that are too large to fit in x10
and x11. They will be converted to a sret by passing a pointer to where
to store the return value.
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@topperc
topperc authored Aug 22, 2024
1 parent c4c5fdd commit 8ba2ae3
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87 changes: 57 additions & 30 deletions llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#include "RISCVMachineFunctionInfo.h"
#include "RISCVSubtarget.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineFrameInfo.h"

Expand Down Expand Up @@ -360,13 +361,7 @@ static bool isSupportedArgumentType(Type *T, const RISCVSubtarget &Subtarget,
// lowerCall.
static bool isSupportedReturnType(Type *T, const RISCVSubtarget &Subtarget,
bool IsLowerRetVal = false) {
// TODO: Integers larger than 2*XLen are passed indirectly which is not
// supported yet.
if (T->isIntegerTy())
return T->getIntegerBitWidth() <= Subtarget.getXLen() * 2;
if (T->isHalfTy() || T->isFloatTy() || T->isDoubleTy())
return true;
if (T->isPointerTy())
if (T->isIntegerTy() || T->isFloatingPointTy() || T->isPointerTy())
return true;

if (T->isArrayTy())
Expand Down Expand Up @@ -394,10 +389,13 @@ bool RISCVCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
assert(!Val == VRegs.empty() && "Return value without a vreg");
MachineInstrBuilder Ret = MIRBuilder.buildInstrNoInsert(RISCV::PseudoRET);

if (!VRegs.empty()) {
if (!FLI.CanLowerReturn) {
insertSRetStores(MIRBuilder, Val->getType(), VRegs, FLI.DemoteRegister);
} else if (!VRegs.empty()) {
const RISCVSubtarget &Subtarget =
MIRBuilder.getMF().getSubtarget<RISCVSubtarget>();
if (!isSupportedReturnType(Val->getType(), Subtarget, /*IsLowerRetVal=*/true))
if (!isSupportedReturnType(Val->getType(), Subtarget,
/*IsLowerRetVal=*/true))
return false;

MachineFunction &MF = MIRBuilder.getMF();
Expand All @@ -418,14 +416,38 @@ bool RISCVCallLowering::lowerReturn(MachineIRBuilder &MIRBuilder,
/*IsRet=*/true, Dispatcher);
RISCVOutgoingValueHandler Handler(MIRBuilder, MF.getRegInfo(), Ret);
if (!determineAndHandleAssignments(Handler, Assigner, SplitRetInfos,
MIRBuilder, CC, F.isVarArg()))
MIRBuilder, CC, F.isVarArg()))
return false;
}

MIRBuilder.insertInstr(Ret);
return true;
}

bool RISCVCallLowering::canLowerReturn(MachineFunction &MF,
CallingConv::ID CallConv,
SmallVectorImpl<BaseArgInfo> &Outs,
bool IsVarArg) const {
SmallVector<CCValAssign, 16> ArgLocs;
const auto &TLI = *getTLI<RISCVTargetLowering>();
CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs,
MF.getFunction().getContext());

RVVArgDispatcher Dispatcher{&MF, &TLI,
ArrayRef(MF.getFunction().getReturnType())};

RISCVABI::ABI ABI = MF.getSubtarget<RISCVSubtarget>().getTargetABI();

for (unsigned I = 0, E = Outs.size(); I < E; ++I) {
MVT VT = MVT::getVT(Outs[I].Ty);
if (RISCV::CC_RISCV(MF.getDataLayout(), ABI, I, VT, VT, CCValAssign::Full,
Outs[I].Flags[0], CCInfo, /*IsFixed=*/true,
/*isRet=*/true, nullptr, TLI, Dispatcher))
return false;
}
return true;
}

/// If there are varargs that were passed in a0-a7, the data in those registers
/// must be copied to the varargs save area on the stack.
void RISCVCallLowering::saveVarArgRegisters(
Expand Down Expand Up @@ -498,24 +520,26 @@ bool RISCVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
const Function &F,
ArrayRef<ArrayRef<Register>> VRegs,
FunctionLoweringInfo &FLI) const {
// Early exit if there are no arguments. varargs are not part of F.args() but
// must be lowered.
if (F.arg_empty() && !F.isVarArg())
return true;
MachineFunction &MF = MIRBuilder.getMF();

const RISCVSubtarget &Subtarget =
MIRBuilder.getMF().getSubtarget<RISCVSubtarget>();
const RISCVSubtarget &Subtarget = MF.getSubtarget<RISCVSubtarget>();
for (auto &Arg : F.args()) {
if (!isSupportedArgumentType(Arg.getType(), Subtarget,
/*IsLowerArgs=*/true))
return false;
}

MachineFunction &MF = MIRBuilder.getMF();
MachineRegisterInfo &MRI = MF.getRegInfo();
const DataLayout &DL = MF.getDataLayout();
CallingConv::ID CC = F.getCallingConv();

SmallVector<ArgInfo, 32> SplitArgInfos;

// Insert the hidden sret parameter if the return value won't fit in the
// return registers.
if (!FLI.CanLowerReturn)
insertSRetIncomingArgument(F, SplitArgInfos, FLI.DemoteRegister, MRI, DL);

SmallVector<Type *, 4> TypeList;
unsigned Index = 0;
for (auto &Arg : F.args()) {
Expand Down Expand Up @@ -625,21 +649,24 @@ bool RISCVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
*Subtarget.getRegBankInfo(), *Call,
Call->getDesc(), Call->getOperand(0), 0);

if (Info.OrigRet.Ty->isVoidTy())
return true;
if (Info.CanLowerReturn && !Info.OrigRet.Ty->isVoidTy()) {
SmallVector<ArgInfo, 4> SplitRetInfos;
splitToValueTypes(Info.OrigRet, SplitRetInfos, DL, CC);

SmallVector<ArgInfo, 4> SplitRetInfos;
splitToValueTypes(Info.OrigRet, SplitRetInfos, DL, CC);
RVVArgDispatcher RetDispatcher{&MF, getTLI<RISCVTargetLowering>(),
ArrayRef(F.getReturnType())};
RISCVIncomingValueAssigner RetAssigner(
CC == CallingConv::Fast ? RISCV::CC_RISCV_FastCC : RISCV::CC_RISCV,
/*IsRet=*/true, RetDispatcher);
RISCVCallReturnHandler RetHandler(MIRBuilder, MF.getRegInfo(), Call);
if (!determineAndHandleAssignments(RetHandler, RetAssigner, SplitRetInfos,
MIRBuilder, CC, Info.IsVarArg))
return false;
}

RVVArgDispatcher RetDispatcher{&MF, getTLI<RISCVTargetLowering>(),
ArrayRef(F.getReturnType())};
RISCVIncomingValueAssigner RetAssigner(
CC == CallingConv::Fast ? RISCV::CC_RISCV_FastCC : RISCV::CC_RISCV,
/*IsRet=*/true, RetDispatcher);
RISCVCallReturnHandler RetHandler(MIRBuilder, MF.getRegInfo(), Call);
if (!determineAndHandleAssignments(RetHandler, RetAssigner, SplitRetInfos,
MIRBuilder, CC, Info.IsVarArg))
return false;
if (!Info.CanLowerReturn)
insertSRetLoads(MIRBuilder, Info.OrigRet.Ty, Info.OrigRet.Regs,
Info.DemoteRegister, Info.DemoteStackIndex);

return true;
}
4 changes: 4 additions & 0 deletions llvm/lib/Target/RISCV/GISel/RISCVCallLowering.h
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,10 @@ class RISCVCallLowering : public CallLowering {
ArrayRef<Register> VRegs,
FunctionLoweringInfo &FLI) const override;

bool canLowerReturn(MachineFunction &MF, CallingConv::ID CallConv,
SmallVectorImpl<BaseArgInfo> &Outs,
bool IsVarArg) const override;

bool lowerFormalArguments(MachineIRBuilder &MIRBuilder, const Function &F,
ArrayRef<ArrayRef<Register>> VRegs,
FunctionLoweringInfo &FLI) const override;
Expand Down
151 changes: 151 additions & 0 deletions llvm/test/CodeGen/RISCV/GlobalISel/irtranslator/calling-conv-ilp32-ilp32f-ilp32d-common.ll
View file
Original file line number Diff line number Diff line change
Expand Up @@ -945,6 +945,54 @@ define i32 @caller_small_struct_ret() nounwind {
ret i32 %5
}

; Check return of >2x xlen scalars

define fp128 @callee_large_scalar_ret() nounwind {
; RV32I-LABEL: name: callee_large_scalar_ret
; RV32I: bb.1 (%ir-block.0):
; RV32I-NEXT: liveins: $x10
; RV32I-NEXT: {{ $}}
; RV32I-NEXT: [[COPY:%[0-9]+]]:_(p0) = COPY $x10
; RV32I-NEXT: [[C:%[0-9]+]]:_(s128) = G_FCONSTANT fp128 0xL00000000000000007FFF000000000000
; RV32I-NEXT: G_STORE [[C]](s128), [[COPY]](p0) :: (store (s128))
; RV32I-NEXT: PseudoRET
ret fp128 0xL00000000000000007FFF000000000000
}

define void @caller_large_scalar_ret() nounwind {
; ILP32-LABEL: name: caller_large_scalar_ret
; ILP32: bb.1 (%ir-block.0):
; ILP32-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_scalar_ret, csr_ilp32_lp64, implicit-def $x1, implicit $x10
; ILP32-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32-NEXT: [[LOAD:%[0-9]+]]:_(s128) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s128) from %stack.0)
; ILP32-NEXT: PseudoRET
;
; ILP32F-LABEL: name: caller_large_scalar_ret
; ILP32F: bb.1 (%ir-block.0):
; ILP32F-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32F-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32F-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32F-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_scalar_ret, csr_ilp32f_lp64f, implicit-def $x1, implicit $x10
; ILP32F-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32F-NEXT: [[LOAD:%[0-9]+]]:_(s128) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s128) from %stack.0)
; ILP32F-NEXT: PseudoRET
;
; ILP32D-LABEL: name: caller_large_scalar_ret
; ILP32D: bb.1 (%ir-block.0):
; ILP32D-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32D-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32D-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32D-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_scalar_ret, csr_ilp32d_lp64d, implicit-def $x1, implicit $x10
; ILP32D-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32D-NEXT: [[LOAD:%[0-9]+]]:_(s128) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s128) from %stack.0)
; ILP32D-NEXT: PseudoRET
%1 = call fp128 @callee_large_scalar_ret()
ret void
}

; Check return of >2x xlen structs

%struct.large = type { i32, i32, i32, i32 }
Expand Down Expand Up @@ -1033,3 +1081,106 @@ define i32 @caller_large_struct_ret() nounwind {
%5 = add i32 %2, %4
ret i32 %5
}

%struct.large2 = type { i32, float, i16, i32 }

define %struct.large2 @callee_large_struct_ret2() nounwind {
; RV32I-LABEL: name: callee_large_struct_ret2
; RV32I: bb.1 (%ir-block.0):
; RV32I-NEXT: liveins: $x10
; RV32I-NEXT: {{ $}}
; RV32I-NEXT: [[COPY:%[0-9]+]]:_(p0) = COPY $x10
; RV32I-NEXT: [[DEF:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
; RV32I-NEXT: [[DEF1:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
; RV32I-NEXT: [[DEF2:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
; RV32I-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
; RV32I-NEXT: [[C1:%[0-9]+]]:_(s32) = G_FCONSTANT float 2.000000e+00
; RV32I-NEXT: [[C2:%[0-9]+]]:_(s16) = G_CONSTANT i16 3
; RV32I-NEXT: [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; RV32I-NEXT: G_STORE [[C]](s32), [[COPY]](p0) :: (store (s32), align 8)
; RV32I-NEXT: [[C4:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; RV32I-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C4]](s32)
; RV32I-NEXT: G_STORE [[C1]](s32), [[PTR_ADD]](p0) :: (store (s32))
; RV32I-NEXT: [[C5:%[0-9]+]]:_(s32) = G_CONSTANT i32 8
; RV32I-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C5]](s32)
; RV32I-NEXT: G_STORE [[C2]](s16), [[PTR_ADD1]](p0) :: (store (s16), align 8)
; RV32I-NEXT: [[C6:%[0-9]+]]:_(s32) = G_CONSTANT i32 12
; RV32I-NEXT: [[PTR_ADD2:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C6]](s32)
; RV32I-NEXT: G_STORE [[C3]](s32), [[PTR_ADD2]](p0) :: (store (s32))
; RV32I-NEXT: PseudoRET
%a = insertvalue %struct.large2 poison, i32 1, 0
%b = insertvalue %struct.large2 %a, float 2.0, 1
%c = insertvalue %struct.large2 %b, i16 3, 2
%d = insertvalue %struct.large2 %c, i32 4, 3
ret %struct.large2 %d
}

define i32 @caller_large_struct_ret2() nounwind {
; ILP32-LABEL: name: caller_large_struct_ret2
; ILP32: bb.1 (%ir-block.0):
; ILP32-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_struct_ret, csr_ilp32_lp64, implicit-def $x1, implicit $x10
; ILP32-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s32) from %stack.0, align 8)
; ILP32-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; ILP32-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C]](s32)
; ILP32-NEXT: [[LOAD1:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD]](p0) :: (load (s32) from %stack.0)
; ILP32-NEXT: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 8
; ILP32-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C1]](s32)
; ILP32-NEXT: [[LOAD2:%[0-9]+]]:_(s16) = G_LOAD [[PTR_ADD1]](p0) :: (load (s16) from %stack.0, align 8)
; ILP32-NEXT: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 12
; ILP32-NEXT: [[PTR_ADD2:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C2]](s32)
; ILP32-NEXT: [[LOAD3:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD2]](p0) :: (load (s32) from %stack.0)
; ILP32-NEXT: [[ADD:%[0-9]+]]:_(s32) = G_ADD [[LOAD]], [[LOAD3]]
; ILP32-NEXT: $x10 = COPY [[ADD]](s32)
; ILP32-NEXT: PseudoRET implicit $x10
;
; ILP32F-LABEL: name: caller_large_struct_ret2
; ILP32F: bb.1 (%ir-block.0):
; ILP32F-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32F-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32F-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32F-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_struct_ret, csr_ilp32f_lp64f, implicit-def $x1, implicit $x10
; ILP32F-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32F-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s32) from %stack.0, align 8)
; ILP32F-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; ILP32F-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C]](s32)
; ILP32F-NEXT: [[LOAD1:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD]](p0) :: (load (s32) from %stack.0)
; ILP32F-NEXT: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 8
; ILP32F-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C1]](s32)
; ILP32F-NEXT: [[LOAD2:%[0-9]+]]:_(s16) = G_LOAD [[PTR_ADD1]](p0) :: (load (s16) from %stack.0, align 8)
; ILP32F-NEXT: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 12
; ILP32F-NEXT: [[PTR_ADD2:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C2]](s32)
; ILP32F-NEXT: [[LOAD3:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD2]](p0) :: (load (s32) from %stack.0)
; ILP32F-NEXT: [[ADD:%[0-9]+]]:_(s32) = G_ADD [[LOAD]], [[LOAD3]]
; ILP32F-NEXT: $x10 = COPY [[ADD]](s32)
; ILP32F-NEXT: PseudoRET implicit $x10
;
; ILP32D-LABEL: name: caller_large_struct_ret2
; ILP32D: bb.1 (%ir-block.0):
; ILP32D-NEXT: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
; ILP32D-NEXT: ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
; ILP32D-NEXT: $x10 = COPY [[FRAME_INDEX]](p0)
; ILP32D-NEXT: PseudoCALL target-flags(riscv-call) @callee_large_struct_ret, csr_ilp32d_lp64d, implicit-def $x1, implicit $x10
; ILP32D-NEXT: ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
; ILP32D-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[FRAME_INDEX]](p0) :: (load (s32) from %stack.0, align 8)
; ILP32D-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; ILP32D-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C]](s32)
; ILP32D-NEXT: [[LOAD1:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD]](p0) :: (load (s32) from %stack.0)
; ILP32D-NEXT: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 8
; ILP32D-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C1]](s32)
; ILP32D-NEXT: [[LOAD2:%[0-9]+]]:_(s16) = G_LOAD [[PTR_ADD1]](p0) :: (load (s16) from %stack.0, align 8)
; ILP32D-NEXT: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 12
; ILP32D-NEXT: [[PTR_ADD2:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[C2]](s32)
; ILP32D-NEXT: [[LOAD3:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD2]](p0) :: (load (s32) from %stack.0)
; ILP32D-NEXT: [[ADD:%[0-9]+]]:_(s32) = G_ADD [[LOAD]], [[LOAD3]]
; ILP32D-NEXT: $x10 = COPY [[ADD]](s32)
; ILP32D-NEXT: PseudoRET implicit $x10
%1 = call %struct.large2 @callee_large_struct_ret()
%2 = extractvalue %struct.large2 %1, 0
%3 = extractvalue %struct.large2 %1, 3
%4 = add i32 %2, %3
ret i32 %4
}
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