1//===-- AMDGPUMachineFunctionInfo.cpp ---------------------------------------=//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "AMDGPUMachineFunction.h"
10#include "AMDGPU.h"
11#include "AMDGPUPerfHintAnalysis.h"
12#include "AMDGPUSubtarget.h"
13#include "Utils/AMDGPUBaseInfo.h"
14#include "llvm/CodeGen/MachineModuleInfo.h"
15#include "llvm/IR/ConstantRange.h"
16#include "llvm/IR/Constants.h"
17#include "llvm/IR/Metadata.h"
18#include "llvm/Target/TargetMachine.h"
19
20using namespace llvm;
21
22static const GlobalVariable *
23getKernelDynLDSGlobalFromFunction(const Function &F) {
24 const Module *M = F.getParent();
25 SmallString<64> KernelDynLDSName("llvm.amdgcn.");
26 KernelDynLDSName += F.getName();
27 KernelDynLDSName += ".dynlds";
28 return M->getNamedGlobal(Name: KernelDynLDSName);
29}
30
31static bool hasLDSKernelArgument(const Function &F) {
32 for (const Argument &Arg : F.args()) {
33 Type *ArgTy = Arg.getType();
34 if (auto PtrTy = dyn_cast<PointerType>(Val: ArgTy)) {
35 if (PtrTy->getAddressSpace() == AMDGPUAS::LOCAL_ADDRESS)
36 return true;
37 }
38 }
39 return false;
40}
41
42AMDGPUMachineFunction::AMDGPUMachineFunction(const Function &F,
43 const AMDGPUSubtarget &ST)
44 : IsEntryFunction(AMDGPU::isEntryFunctionCC(CC: F.getCallingConv())),
45 IsModuleEntryFunction(
46 AMDGPU::isModuleEntryFunctionCC(CC: F.getCallingConv())),
47 IsChainFunction(AMDGPU::isChainCC(CC: F.getCallingConv())),
48 NoSignedZerosFPMath(false) {
49
50 // FIXME: Should initialize KernArgSize based on ExplicitKernelArgOffset,
51 // except reserved size is not correctly aligned.
52
53 Attribute MemBoundAttr = F.getFnAttribute(Kind: "amdgpu-memory-bound");
54 MemoryBound = MemBoundAttr.getValueAsBool();
55
56 Attribute WaveLimitAttr = F.getFnAttribute(Kind: "amdgpu-wave-limiter");
57 WaveLimiter = WaveLimitAttr.getValueAsBool();
58
59 // FIXME: How is this attribute supposed to interact with statically known
60 // global sizes?
61 StringRef S = F.getFnAttribute(Kind: "amdgpu-gds-size").getValueAsString();
62 if (!S.empty())
63 S.consumeInteger(Radix: 0, Result&: GDSSize);
64
65 // Assume the attribute allocates before any known GDS globals.
66 StaticGDSSize = GDSSize;
67
68 // Second value, if present, is the maximum value that can be assigned.
69 // Useful in PromoteAlloca or for LDS spills. Could be used for diagnostics
70 // during codegen.
71 std::pair<unsigned, unsigned> LDSSizeRange = AMDGPU::getIntegerPairAttribute(
72 F, Name: "amdgpu-lds-size", Default: {0, UINT32_MAX}, OnlyFirstRequired: true);
73
74 // The two separate variables are only profitable when the LDS module lowering
75 // pass is disabled. If graphics does not use dynamic LDS, this is never
76 // profitable. Leaving cleanup for a later change.
77 LDSSize = LDSSizeRange.first;
78 StaticLDSSize = LDSSize;
79
80 CallingConv::ID CC = F.getCallingConv();
81 if (CC == CallingConv::AMDGPU_KERNEL || CC == CallingConv::SPIR_KERNEL)
82 ExplicitKernArgSize = ST.getExplicitKernArgSize(F, MaxAlign&: MaxKernArgAlign);
83
84 // FIXME: Shouldn't be target specific
85 Attribute NSZAttr = F.getFnAttribute(Kind: "no-signed-zeros-fp-math");
86 NoSignedZerosFPMath =
87 NSZAttr.isStringAttribute() && NSZAttr.getValueAsString() == "true";
88
89 const GlobalVariable *DynLdsGlobal = getKernelDynLDSGlobalFromFunction(F);
90 if (DynLdsGlobal || hasLDSKernelArgument(F))
91 UsesDynamicLDS = true;
92}
93
94unsigned AMDGPUMachineFunction::allocateLDSGlobal(const DataLayout &DL,
95 const GlobalVariable &GV,
96 Align Trailing) {
97 auto Entry = LocalMemoryObjects.insert(KV: std::pair(&GV, 0));
98 if (!Entry.second)
99 return Entry.first->second;
100
101 Align Alignment =
102 DL.getValueOrABITypeAlignment(Alignment: GV.getAlign(), Ty: GV.getValueType());
103
104 unsigned Offset;
105 if (GV.getAddressSpace() == AMDGPUAS::LOCAL_ADDRESS) {
106
107 std::optional<uint32_t> MaybeAbs = getLDSAbsoluteAddress(GV);
108 if (MaybeAbs) {
109 // Absolute address LDS variables that exist prior to the LDS lowering
110 // pass raise a fatal error in that pass. These failure modes are only
111 // reachable if that lowering pass is disabled or broken. If/when adding
112 // support for absolute addresses on user specified variables, the
113 // alignment check moves to the lowering pass and the frame calculation
114 // needs to take the user variables into consideration.
115
116 uint32_t ObjectStart = *MaybeAbs;
117
118 if (ObjectStart != alignTo(Size: ObjectStart, A: Alignment)) {
119 report_fatal_error(reason: "Absolute address LDS variable inconsistent with "
120 "variable alignment");
121 }
122
123 if (isModuleEntryFunction()) {
124 // If this is a module entry function, we can also sanity check against
125 // the static frame. Strictly it would be better to check against the
126 // attribute, i.e. that the variable is within the always-allocated
127 // section, and not within some other non-absolute-address object
128 // allocated here, but the extra error detection is minimal and we would
129 // have to pass the Function around or cache the attribute value.
130 uint32_t ObjectEnd =
131 ObjectStart + DL.getTypeAllocSize(Ty: GV.getValueType());
132 if (ObjectEnd > StaticLDSSize) {
133 report_fatal_error(
134 reason: "Absolute address LDS variable outside of static frame");
135 }
136 }
137
138 Entry.first->second = ObjectStart;
139 return ObjectStart;
140 }
141
142 /// TODO: We should sort these to minimize wasted space due to alignment
143 /// padding. Currently the padding is decided by the first encountered use
144 /// during lowering.
145 Offset = StaticLDSSize = alignTo(Size: StaticLDSSize, A: Alignment);
146
147 StaticLDSSize += DL.getTypeAllocSize(Ty: GV.getValueType());
148
149 // Align LDS size to trailing, e.g. for aligning dynamic shared memory
150 LDSSize = alignTo(Size: StaticLDSSize, A: Trailing);
151 } else {
152 assert(GV.getAddressSpace() == AMDGPUAS::REGION_ADDRESS &&
153 "expected region address space");
154
155 Offset = StaticGDSSize = alignTo(Size: StaticGDSSize, A: Alignment);
156 StaticGDSSize += DL.getTypeAllocSize(Ty: GV.getValueType());
157
158 // FIXME: Apply alignment of dynamic GDS
159 GDSSize = StaticGDSSize;
160 }
161
162 Entry.first->second = Offset;
163 return Offset;
164}
165
166std::optional<uint32_t>
167AMDGPUMachineFunction::getLDSKernelIdMetadata(const Function &F) {
168 // TODO: Would be more consistent with the abs symbols to use a range
169 MDNode *MD = F.getMetadata(Kind: "llvm.amdgcn.lds.kernel.id");
170 if (MD && MD->getNumOperands() == 1) {
171 if (ConstantInt *KnownSize =
172 mdconst::extract<ConstantInt>(MD: MD->getOperand(I: 0))) {
173 uint64_t ZExt = KnownSize->getZExtValue();
174 if (ZExt <= UINT32_MAX) {
175 return ZExt;
176 }
177 }
178 }
179 return {};
180}
181
182std::optional<uint32_t>
183AMDGPUMachineFunction::getLDSAbsoluteAddress(const GlobalValue &GV) {
184 if (GV.getAddressSpace() != AMDGPUAS::LOCAL_ADDRESS)
185 return {};
186
187 std::optional<ConstantRange> AbsSymRange = GV.getAbsoluteSymbolRange();
188 if (!AbsSymRange)
189 return {};
190
191 if (const APInt *V = AbsSymRange->getSingleElement()) {
192 std::optional<uint64_t> ZExt = V->tryZExtValue();
193 if (ZExt && (*ZExt <= UINT32_MAX)) {
194 return *ZExt;
195 }
196 }
197
198 return {};
199}
200
201void AMDGPUMachineFunction::setDynLDSAlign(const Function &F,
202 const GlobalVariable &GV) {
203 const Module *M = F.getParent();
204 const DataLayout &DL = M->getDataLayout();
205 assert(DL.getTypeAllocSize(GV.getValueType()).isZero());
206
207 Align Alignment =
208 DL.getValueOrABITypeAlignment(Alignment: GV.getAlign(), Ty: GV.getValueType());
209 if (Alignment <= DynLDSAlign)
210 return;
211
212 LDSSize = alignTo(Size: StaticLDSSize, A: Alignment);
213 DynLDSAlign = Alignment;
214
215 // If there is a dynamic LDS variable associated with this function F, every
216 // further dynamic LDS instance (allocated by calling setDynLDSAlign) must
217 // map to the same address. This holds because no LDS is allocated after the
218 // lowering pass if there are dynamic LDS variables present.
219 const GlobalVariable *Dyn = getKernelDynLDSGlobalFromFunction(F);
220 if (Dyn) {
221 unsigned Offset = LDSSize; // return this?
222 std::optional<uint32_t> Expect = getLDSAbsoluteAddress(GV: *Dyn);
223 if (!Expect || (Offset != *Expect)) {
224 report_fatal_error(reason: "Inconsistent metadata on dynamic LDS variable");
225 }
226 }
227}
228
229void AMDGPUMachineFunction::setUsesDynamicLDS(bool DynLDS) {
230 UsesDynamicLDS = DynLDS;
231}
232
233bool AMDGPUMachineFunction::isDynamicLDSUsed() const { return UsesDynamicLDS; }
234

source code of llvm/lib/Target/AMDGPU/AMDGPUMachineFunction.cpp