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[ARM] Treat memcpy/memset/memmove as call instructions for low overhead loops 

If an instruction will be lowered to a call there is no advantage of
using a low overhead loop as the LR register will need to be spilled and
reloaded around the call, and the low overhead will end up being
reverted. This teaches our hardware loop lowering that these memory
intrinsics will be calls under certain situations.

Differential Revision: https://reviews.llvm.org/D90439
This commit is contained in:
David Green 2020-11-03 11:53:09 +00:00
parent 785080e3fa
commit e474499402
3 changed files with 105 additions and 59 deletions
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109
llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
View File

@ -951,39 +951,85 @@ bool ARMTTIImpl::isLegalMaskedGather(Type *Ty, Align Alignment) {
(EltWidth == 16 && Alignment >= 2) || EltWidth == 8);
}
int ARMTTIImpl::getMemcpyCost(const Instruction *I) {
const MemCpyInst *MI = dyn_cast<MemCpyInst>(I);
assert(MI && "MemcpyInst expected");
ConstantInt *C = dyn_cast<ConstantInt>(MI->getLength());
// To model the cost of a library call, we assume 1 for the call, and
// 3 for the argument setup.
const unsigned LibCallCost = 4;
// If 'size' is not a constant, a library call will be generated.
if (!C)
return LibCallCost;
const unsigned Size = C->getValue().getZExtValue();
const Align DstAlign = *MI->getDestAlign();
const Align SrcAlign = *MI->getSourceAlign();
/// Given a memcpy/memset/memmove instruction, return the number of memory
/// operations performed, via querying findOptimalMemOpLowering. Returns -1 if a
/// call is used.
int ARMTTIImpl::getNumMemOps(const IntrinsicInst *I) const {
MemOp MOp;
unsigned DstAddrSpace = ~0u;
unsigned SrcAddrSpace = ~0u;
const Function *F = I->getParent()->getParent();
const unsigned Limit = TLI->getMaxStoresPerMemmove(F->hasMinSize());
std::vector<EVT> MemOps;
if (const auto *MC = dyn_cast<MemTransferInst>(I)) {
ConstantInt *C = dyn_cast<ConstantInt>(MC->getLength());
// If 'size' is not a constant, a library call will be generated.
if (!C)
return -1;
const unsigned Size = C->getValue().getZExtValue();
const Align DstAlign = *MC->getDestAlign();
const Align SrcAlign = *MC->getSourceAlign();
const Function *F = I->getParent()->getParent();
std::vector<EVT> MemOps;
MOp = MemOp::Copy(Size, /*DstAlignCanChange*/ false, DstAlign, SrcAlign,
/*IsVolatile*/ false);
DstAddrSpace = MC->getDestAddressSpace();
SrcAddrSpace = MC->getSourceAddressSpace();
}
else if (const auto *MS = dyn_cast<MemSetInst>(I)) {
ConstantInt *C = dyn_cast<ConstantInt>(MS->getLength());
// If 'size' is not a constant, a library call will be generated.
if (!C)
return -1;
const unsigned Size = C->getValue().getZExtValue();
const Align DstAlign = *MS->getDestAlign();
MOp = MemOp::Set(Size, /*DstAlignCanChange*/ false, DstAlign,
/*IsZeroMemset*/ false, /*IsVolatile*/ false);
DstAddrSpace = MS->getDestAddressSpace();
}
else
llvm_unreachable("Expected a memcpy/move or memset!");
unsigned Limit, Factor = 2;
switch(I->getIntrinsicID()) {
case Intrinsic::memcpy:
Limit = TLI->getMaxStoresPerMemcpy(F->hasMinSize());
break;
case Intrinsic::memmove:
Limit = TLI->getMaxStoresPerMemmove(F->hasMinSize());
break;
case Intrinsic::memset:
Limit = TLI->getMaxStoresPerMemset(F->hasMinSize());
Factor = 1;
break;
default:
llvm_unreachable("Expected a memcpy/move or memset!");
}
// MemOps will be poplulated with a list of data types that needs to be
// loaded and stored. That's why we multiply the number of elements by 2 to
// get the cost for this memcpy.
std::vector<EVT> MemOps;
if (getTLI()->findOptimalMemOpLowering(
MemOps, Limit,
MemOp::Copy(Size, /*DstAlignCanChange*/ false, DstAlign, SrcAlign,
/*IsVolatile*/ true),
MI->getDestAddressSpace(), MI->getSourceAddressSpace(),
F->getAttributes()))
return MemOps.size() * 2;
MemOps, Limit, MOp, DstAddrSpace,
SrcAddrSpace, F->getAttributes()))
return MemOps.size() * Factor;
// If we can't find an optimal memop lowering, return the default cost
return LibCallCost;
return -1;
}
int ARMTTIImpl::getMemcpyCost(const Instruction *I) {
int NumOps = getNumMemOps(cast<IntrinsicInst>(I));
// To model the cost of a library call, we assume 1 for the call, and
// 3 for the argument setup.
if (NumOps == -1)
return 4;
return NumOps;
}
int ARMTTIImpl::getShuffleCost(TTI::ShuffleKind Kind, VectorType *Tp,
@ -1520,9 +1566,16 @@ bool ARMTTIImpl::maybeLoweredToCall(Instruction &I) {
// Check if an intrinsic will be lowered to a call and assume that any
// other CallInst will generate a bl.
if (auto *Call = dyn_cast<CallInst>(&I)) {
if (isa<IntrinsicInst>(Call)) {
if (const Function *F = Call->getCalledFunction())
return isLoweredToCall(F);
if (auto *II = dyn_cast<IntrinsicInst>(Call)) {
switch(II->getIntrinsicID()) {
case Intrinsic::memcpy:
case Intrinsic::memset:
case Intrinsic::memmove:
return getNumMemOps(II) == -1;
default:
if (const Function *F = Call->getCalledFunction())
return isLoweredToCall(F);
}
}
return true;
}

2
llvm/lib/Target/ARM/ARMTargetTransformInfo.h
View File

@ -181,6 +181,8 @@ public:
int getMemcpyCost(const Instruction *I);
int getNumMemOps(const IntrinsicInst *I) const;
int getShuffleCost(TTI::ShuffleKind Kind, VectorType *Tp, int Index,
VectorType *SubTp);

53
llvm/test/CodeGen/Thumb2/LowOverheadLoops/memcall.ll
View File

@ -12,23 +12,20 @@ define void @test_memcpy(i32* nocapture %x, i32* nocapture readonly %y, i32 %n,
; CHECK-NEXT: blt .LBB0_3
; CHECK-NEXT: @ %bb.1: @ %for.body.preheader
; CHECK-NEXT: mov r8, r3
; CHECK-NEXT: mov lr, r2
; CHECK-NEXT: mov r5, r2
; CHECK-NEXT: mov r9, r1
; CHECK-NEXT: mov r6, r0
; CHECK-NEXT: lsls r7, r3, #2
; CHECK-NEXT: movs r4, #0
; CHECK-NEXT: mov r7, r0
; CHECK-NEXT: lsls r4, r3, #2
; CHECK-NEXT: movs r6, #0
; CHECK-NEXT: .LBB0_2: @ %for.body
; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
; CHECK-NEXT: adds r0, r6, r4
; CHECK-NEXT: add.w r1, r9, r4
; CHECK-NEXT: adds r0, r7, r6
; CHECK-NEXT: add.w r1, r9, r6
; CHECK-NEXT: mov r2, r8
; CHECK-NEXT: mov r5, lr
; CHECK-NEXT: bl __aeabi_memcpy4
; CHECK-NEXT: mov lr, r5
; CHECK-NEXT: add r4, r7
; CHECK-NEXT: subs.w lr, lr, #1
; CHECK-NEXT: add r6, r4
; CHECK-NEXT: subs r5, #1
; CHECK-NEXT: bne .LBB0_2
; CHECK-NEXT: b .LBB0_3
; CHECK-NEXT: .LBB0_3: @ %for.cond.cleanup
; CHECK-NEXT: add sp, #4
; CHECK-NEXT: pop.w {r4, r5, r6, r7, r8, r9, pc}
@ -64,20 +61,17 @@ define void @test_memset(i32* nocapture %x, i32 %n, i32 %m) {
; CHECK-NEXT: blt .LBB1_3
; CHECK-NEXT: @ %bb.1: @ %for.body.preheader
; CHECK-NEXT: mov r4, r2
; CHECK-NEXT: mov lr, r1
; CHECK-NEXT: mov r5, r0
; CHECK-NEXT: lsls r6, r2, #2
; CHECK-NEXT: mov r5, r1
; CHECK-NEXT: mov r6, r0
; CHECK-NEXT: lsls r7, r2, #2
; CHECK-NEXT: .LBB1_2: @ %for.body
; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
; CHECK-NEXT: mov r0, r5
; CHECK-NEXT: mov r0, r6
; CHECK-NEXT: mov r1, r4
; CHECK-NEXT: mov r7, lr
; CHECK-NEXT: bl __aeabi_memclr4
; CHECK-NEXT: mov lr, r7
; CHECK-NEXT: add r5, r6
; CHECK-NEXT: subs.w lr, lr, #1
; CHECK-NEXT: add r6, r7
; CHECK-NEXT: subs r5, #1
; CHECK-NEXT: bne .LBB1_2
; CHECK-NEXT: b .LBB1_3
; CHECK-NEXT: .LBB1_3: @ %for.cond.cleanup
; CHECK-NEXT: add sp, #4
; CHECK-NEXT: pop {r4, r5, r6, r7, pc}
@ -110,23 +104,20 @@ define void @test_memmove(i32* nocapture %x, i32* nocapture readonly %y, i32 %n,
; CHECK-NEXT: blt .LBB2_3
; CHECK-NEXT: @ %bb.1: @ %for.body.preheader
; CHECK-NEXT: mov r8, r3
; CHECK-NEXT: mov lr, r2
; CHECK-NEXT: mov r5, r2
; CHECK-NEXT: mov r9, r1
; CHECK-NEXT: mov r6, r0
; CHECK-NEXT: lsls r7, r3, #2
; CHECK-NEXT: movs r4, #0
; CHECK-NEXT: mov r7, r0
; CHECK-NEXT: lsls r4, r3, #2
; CHECK-NEXT: movs r6, #0
; CHECK-NEXT: .LBB2_2: @ %for.body
; CHECK-NEXT: @ =>This Inner Loop Header: Depth=1
; CHECK-NEXT: adds r0, r6, r4
; CHECK-NEXT: add.w r1, r9, r4
; CHECK-NEXT: adds r0, r7, r6
; CHECK-NEXT: add.w r1, r9, r6
; CHECK-NEXT: mov r2, r8
; CHECK-NEXT: mov r5, lr
; CHECK-NEXT: bl __aeabi_memmove4
; CHECK-NEXT: mov lr, r5
; CHECK-NEXT: add r4, r7
; CHECK-NEXT: subs.w lr, lr, #1
; CHECK-NEXT: add r6, r4
; CHECK-NEXT: subs r5, #1
; CHECK-NEXT: bne .LBB2_2
; CHECK-NEXT: b .LBB2_3
; CHECK-NEXT: .LBB2_3: @ %for.cond.cleanup
; CHECK-NEXT: add sp, #4
; CHECK-NEXT: pop.w {r4, r5, r6, r7, r8, r9, pc}