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AMDGPU: More bits of frame index are known to be zero

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The maximum private allocation for the whole GPU is 4G,
so the maximum possible index for a single workitem is the
maximum size divided by the smallest granularity for a dispatch.

This increases the number of known zero high bits, which
enables more offset folding. The maximum private size per
workitem with this is 128M but may be smaller still.

llvm-svn: 262153
This commit is contained in:
Matt Arsenault 2016-02-27 20:26:57 +00:00
parent eedb835102
commit cd69621a21
6 changed files with 40 additions and 42 deletions
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8
lib/Target/AMDGPU/AMDGPU.td
View File

@ -198,14 +198,6 @@ def FeatureMaxPrivateElementSize4 : FeatureMaxPrivateElementSize<4>;
def FeatureMaxPrivateElementSize8 : FeatureMaxPrivateElementSize<8>;
def FeatureMaxPrivateElementSize16 : FeatureMaxPrivateElementSize<16>;
def FeatureEnableHugeScratchBuffer : SubtargetFeature<
"huge-scratch-buffer",
"EnableHugeScratchBuffer",
"true",
"Enable scratch buffer sizes greater than 128 GB"
>;
def FeatureVGPRSpilling : SubtargetFeature<"vgpr-spilling",
"EnableVGPRSpilling",
"true",

2
lib/Target/AMDGPU/AMDGPUSubtarget.cpp
View File

@ -84,7 +84,7 @@ AMDGPUSubtarget::AMDGPUSubtarget(const Triple &TT, StringRef GPU, StringRef FS,
GCN1Encoding(false), GCN3Encoding(false), CIInsts(false),
HasSMemRealTime(false), Has16BitInsts(false),
LDSBankCount(0),
IsaVersion(ISAVersion0_0_0), EnableHugeScratchBuffer(false),
IsaVersion(ISAVersion0_0_0),
EnableSIScheduler(false), FrameLowering(nullptr),
InstrItins(getInstrItineraryForCPU(GPU)), TargetTriple(TT) {

5
lib/Target/AMDGPU/AMDGPUSubtarget.h
View File

@ -93,7 +93,6 @@ private:
bool FeatureDisable;
int LDSBankCount;
unsigned IsaVersion;
bool EnableHugeScratchBuffer;
bool EnableSIScheduler;
std::unique_ptr<AMDGPUFrameLowering> FrameLowering;
@ -293,10 +292,6 @@ public:
return false;
}
bool enableHugeScratchBuffer() const {
return EnableHugeScratchBuffer;
}
bool enableSIScheduler() const {
return EnableSIScheduler;
}

40
lib/Target/AMDGPU/SIISelLowering.cpp
View File

@ -1178,25 +1178,35 @@ SDValue SITargetLowering::LowerFrameIndex(SDValue Op, SelectionDAG &DAG) const {
FrameIndexSDNode *FINode = cast<FrameIndexSDNode>(Op);
unsigned FrameIndex = FINode->getIndex();
// A FrameIndex node represents a 32-bit offset into scratch memory. If
// the high bit of a frame index offset were to be set, this would mean
// that it represented an offset of ~2GB * 64 = ~128GB from the start of the
// scratch buffer, with 64 being the number of threads per wave.
// A FrameIndex node represents a 32-bit offset into scratch memory. If the
// high bit of a frame index offset were to be set, this would mean that it
// represented an offset of ~2GB * 64 = ~128GB from the start of the scratch
// buffer, with 64 being the number of threads per wave.
//
// If we know the machine uses less than 128GB of scratch, then we can
// amrk the high bit of the FrameIndex node as known zero,
// which is important, because it means in most situations we can
// prove that values derived from FrameIndex nodes are non-negative.
// This enables us to take advantage of more addressing modes when
// accessing scratch buffers, since for scratch reads/writes, the register
// offset must always be positive.
// The maximum private allocation for the entire GPU is 4G, and we are
// concerned with the largest the index could ever be for an individual
// workitem. This will occur with the minmum dispatch size. If a program
// requires more, the dispatch size will be reduced.
//
// With this limit, we can mark the high bit of the FrameIndex node as known
// zero, which is important, because it means in most situations we can prove
// that values derived from FrameIndex nodes are non-negative. This enables us
// to take advantage of more addressing modes when accessing scratch buffers,
// since for scratch reads/writes, the register offset must always be
// positive.
uint64_t MaxGPUAlloc = UINT64_C(4) * 1024 * 1024 * 1024;
// XXX - It is unclear if partial dispatch works. Assume it works at half wave
// granularity. It is probably a full wave.
uint64_t MinGranularity = 32;
unsigned KnownBits = Log2_64(MaxGPUAlloc / MinGranularity);
EVT ExtVT = EVT::getIntegerVT(*DAG.getContext(), KnownBits);
SDValue TFI = DAG.getTargetFrameIndex(FrameIndex, MVT::i32);
if (Subtarget->enableHugeScratchBuffer())
return TFI;
return DAG.getNode(ISD::AssertZext, SL, MVT::i32, TFI,
DAG.getValueType(EVT::getIntegerVT(*DAG.getContext(), 31)));
DAG.getValueType(ExtVT));
}
bool SITargetLowering::isCFIntrinsic(const SDNode *Intr) const {

18
test/CodeGen/AMDGPU/private-element-size.ll
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@ -33,9 +33,9 @@
; HSA-ELT4-DAG: buffer_store_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:28{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:4{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:8{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:12{{$}}
define void @private_elt_size_v4i32(<4 x i32> addrspace(1)* %out, i32 addrspace(1)* %index.array) #0 {
entry:
%tid = call i32 @llvm.amdgcn.workitem.id.x()
@ -99,10 +99,14 @@ entry:
; HSA-ELT4-DAG: buffer_store_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:56{{$}}
; HSA-ELT4-DAG: buffer_store_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:60{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:4{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:8{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:12{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:16{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:20{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:24{{$}}
; HSA-ELT4-DAG: buffer_load_dword {{v[0-9]+}}, v{{[0-9]+}}, s[0:3], s9 offen offset:28{{$}}
define void @private_elt_size_v8i32(<8 x i32> addrspace(1)* %out, i32 addrspace(1)* %index.array) #0 {
entry:
%tid = call i32 @llvm.amdgcn.workitem.id.x()

9
test/CodeGen/AMDGPU/scratch-buffer.ll
View File

@ -1,7 +1,5 @@
; RUN: llc -verify-machineinstrs -march=amdgcn -mcpu=SI < %s | FileCheck --check-prefix=GCN --check-prefix=DEFAULT-SCRATCH %s
; RUN: llc -verify-machineinstrs -march=amdgcn -mcpu=tonga < %s | FileCheck --check-prefix=GCN --check-prefix=DEFAULT-SCRATCH %s
; RUN: llc -verify-machineinstrs -march=amdgcn -mattr=+huge-scratch-buffer -mcpu=SI < %s | FileCheck --check-prefix=GCN --check-prefix=HUGE-SCRATCH %s
; RUN: llc -verify-machineinstrs -march=amdgcn -mattr=+huge-scratch-buffer -mcpu=tonga < %s | FileCheck --check-prefix=GCN --check-prefix=HUGE-SCRATCH %s
; RUN: llc -verify-machineinstrs -march=amdgcn < %s | FileCheck -check-prefix=GCN %s
; RUN: llc -verify-machineinstrs -march=amdgcn -mcpu=tonga < %s | FileCheck -check-prefix=GCN %s
; When a frame index offset is more than 12-bits, make sure we don't store
; it in mubuf's offset field.
@ -102,8 +100,7 @@ entry:
}
; GCN-LABEL: @pos_vaddr_offse
; DEFAULT-SCRATCH: buffer_store_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], s{{[0-9]+}} offen offset:16
; HUGE-SCRATCH: buffer_store_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], s{{[0-9]+}} offen{{$}}
; GCN: buffer_store_dword v{{[0-9]+}}, v{{[0-9]+}}, s[{{[0-9]+:[0-9]+}}], s{{[0-9]+}} offen offset:16
define void @pos_vaddr_offset(i32 addrspace(1)* %out, i32 %offset) {
entry:
%array = alloca [8192 x i32]