Bug Summary

File:llvm/lib/Target/ARM/ARMCallingConv.cpp
Warning:line 92, column 16
1st function call argument is an uninitialized value

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name ARMCallingConv.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Target/ARM -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Target/ARM -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Target/ARM -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/include -I /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/include -D NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/build-llvm/lib/Target/ARM -fdebug-prefix-map=/build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e=. -ferror-limit 19 -fvisibility hidden -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-09-04-040900-46481-1 -x c++ /build/llvm-toolchain-snapshot-14~++20210903100615+fd66b44ec19e/llvm/lib/Target/ARM/ARMCallingConv.cpp
1//=== ARMCallingConv.cpp - ARM Custom CC Routines ---------------*- C++ -*-===//
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// This file contains the custom routines for the ARM Calling Convention that
10// aren't done by tablegen, and includes the table generated implementations.
11//
12//===----------------------------------------------------------------------===//
13
14#include "ARM.h"
15#include "ARMCallingConv.h"
16#include "ARMSubtarget.h"
17#include "ARMRegisterInfo.h"
18using namespace llvm;
19
20// APCS f64 is in register pairs, possibly split to stack
21static bool f64AssignAPCS(unsigned ValNo, MVT ValVT, MVT LocVT,
22 CCValAssign::LocInfo LocInfo,
23 CCState &State, bool CanFail) {
24 static const MCPhysReg RegList[] = { ARM::R0, ARM::R1, ARM::R2, ARM::R3 };
25
26 // Try to get the first register.
27 if (unsigned Reg = State.AllocateReg(RegList))
28 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, Reg, LocVT, LocInfo));
29 else {
30 // For the 2nd half of a v2f64, do not fail.
31 if (CanFail)
32 return false;
33
34 // Put the whole thing on the stack.
35 State.addLoc(CCValAssign::getCustomMem(
36 ValNo, ValVT, State.AllocateStack(8, Align(4)), LocVT, LocInfo));
37 return true;
38 }
39
40 // Try to get the second register.
41 if (unsigned Reg = State.AllocateReg(RegList))
42 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, Reg, LocVT, LocInfo));
43 else
44 State.addLoc(CCValAssign::getCustomMem(
45 ValNo, ValVT, State.AllocateStack(4, Align(4)), LocVT, LocInfo));
46 return true;
47}
48
49static bool CC_ARM_APCS_Custom_f64(unsigned ValNo, MVT ValVT, MVT LocVT,
50 CCValAssign::LocInfo LocInfo,
51 ISD::ArgFlagsTy ArgFlags,
52 CCState &State) {
53 if (!f64AssignAPCS(ValNo, ValVT, LocVT, LocInfo, State, true))
54 return false;
55 if (LocVT == MVT::v2f64 &&
56 !f64AssignAPCS(ValNo, ValVT, LocVT, LocInfo, State, false))
57 return false;
58 return true; // we handled it
59}
60
61// AAPCS f64 is in aligned register pairs
62static bool f64AssignAAPCS(unsigned ValNo, MVT ValVT, MVT LocVT,
63 CCValAssign::LocInfo LocInfo,
64 CCState &State, bool CanFail) {
65 static const MCPhysReg HiRegList[] = { ARM::R0, ARM::R2 };
66 static const MCPhysReg LoRegList[] = { ARM::R1, ARM::R3 };
67 static const MCPhysReg ShadowRegList[] = { ARM::R0, ARM::R1 };
68 static const MCPhysReg GPRArgRegs[] = { ARM::R0, ARM::R1, ARM::R2, ARM::R3 };
69
70 unsigned Reg = State.AllocateReg(HiRegList, ShadowRegList);
71 if (Reg == 0) {
2
Assuming 'Reg' is not equal to 0
3
Taking false branch
72
73 // If we had R3 unallocated only, now we still must to waste it.
74 Reg = State.AllocateReg(GPRArgRegs);
75 assert((!Reg || Reg == ARM::R3) && "Wrong GPRs usage for f64")(static_cast<void> (0));
76
77 // For the 2nd half of a v2f64, do not just fail.
78 if (CanFail)
79 return false;
80
81 // Put the whole thing on the stack.
82 State.addLoc(CCValAssign::getCustomMem(
83 ValNo, ValVT, State.AllocateStack(8, Align(8)), LocVT, LocInfo));
84 return true;
85 }
86
87 unsigned i;
88 for (i = 0; i < 2; ++i)
4
Loop condition is true. Entering loop body
7
Loop condition is true. Entering loop body
10
The value 2 is assigned to 'i'
11
Loop condition is false. Execution continues on line 92
89 if (HiRegList[i] == Reg)
5
Assuming the condition is false
6
Taking false branch
8
Assuming the condition is false
9
Taking false branch
90 break;
91
92 unsigned T = State.AllocateReg(LoRegList[i]);
12
1st function call argument is an uninitialized value
93 (void)T;
94 assert(T == LoRegList[i] && "Could not allocate register")(static_cast<void> (0));
95
96 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, Reg, LocVT, LocInfo));
97 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, LoRegList[i],
98 LocVT, LocInfo));
99 return true;
100}
101
102static bool CC_ARM_AAPCS_Custom_f64(unsigned ValNo, MVT ValVT, MVT LocVT,
103 CCValAssign::LocInfo LocInfo,
104 ISD::ArgFlagsTy ArgFlags,
105 CCState &State) {
106 if (!f64AssignAAPCS(ValNo, ValVT, LocVT, LocInfo, State, true))
1
Calling 'f64AssignAAPCS'
107 return false;
108 if (LocVT == MVT::v2f64 &&
109 !f64AssignAAPCS(ValNo, ValVT, LocVT, LocInfo, State, false))
110 return false;
111 return true; // we handled it
112}
113
114static bool f64RetAssign(unsigned ValNo, MVT ValVT, MVT LocVT,
115 CCValAssign::LocInfo LocInfo, CCState &State) {
116 static const MCPhysReg HiRegList[] = { ARM::R0, ARM::R2 };
117 static const MCPhysReg LoRegList[] = { ARM::R1, ARM::R3 };
118
119 unsigned Reg = State.AllocateReg(HiRegList, LoRegList);
120 if (Reg == 0)
121 return false; // we didn't handle it
122
123 unsigned i;
124 for (i = 0; i < 2; ++i)
125 if (HiRegList[i] == Reg)
126 break;
127
128 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, Reg, LocVT, LocInfo));
129 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, LoRegList[i],
130 LocVT, LocInfo));
131 return true;
132}
133
134static bool RetCC_ARM_APCS_Custom_f64(unsigned ValNo, MVT ValVT, MVT LocVT,
135 CCValAssign::LocInfo LocInfo,
136 ISD::ArgFlagsTy ArgFlags,
137 CCState &State) {
138 if (!f64RetAssign(ValNo, ValVT, LocVT, LocInfo, State))
139 return false;
140 if (LocVT == MVT::v2f64 && !f64RetAssign(ValNo, ValVT, LocVT, LocInfo, State))
141 return false;
142 return true; // we handled it
143}
144
145static bool RetCC_ARM_AAPCS_Custom_f64(unsigned ValNo, MVT ValVT, MVT LocVT,
146 CCValAssign::LocInfo LocInfo,
147 ISD::ArgFlagsTy ArgFlags,
148 CCState &State) {
149 return RetCC_ARM_APCS_Custom_f64(ValNo, ValVT, LocVT, LocInfo, ArgFlags,
150 State);
151}
152
153static const MCPhysReg RRegList[] = { ARM::R0, ARM::R1, ARM::R2, ARM::R3 };
154
155static const MCPhysReg SRegList[] = { ARM::S0, ARM::S1, ARM::S2, ARM::S3,
156 ARM::S4, ARM::S5, ARM::S6, ARM::S7,
157 ARM::S8, ARM::S9, ARM::S10, ARM::S11,
158 ARM::S12, ARM::S13, ARM::S14, ARM::S15 };
159static const MCPhysReg DRegList[] = { ARM::D0, ARM::D1, ARM::D2, ARM::D3,
160 ARM::D4, ARM::D5, ARM::D6, ARM::D7 };
161static const MCPhysReg QRegList[] = { ARM::Q0, ARM::Q1, ARM::Q2, ARM::Q3 };
162
163
164// Allocate part of an AAPCS HFA or HVA. We assume that each member of the HA
165// has InConsecutiveRegs set, and that the last member also has
166// InConsecutiveRegsLast set. We must process all members of the HA before
167// we can allocate it, as we need to know the total number of registers that
168// will be needed in order to (attempt to) allocate a contiguous block.
169static bool CC_ARM_AAPCS_Custom_Aggregate(unsigned ValNo, MVT ValVT,
170 MVT LocVT,
171 CCValAssign::LocInfo LocInfo,
172 ISD::ArgFlagsTy ArgFlags,
173 CCState &State) {
174 SmallVectorImpl<CCValAssign> &PendingMembers = State.getPendingLocs();
175
176 // AAPCS HFAs must have 1-4 elements, all of the same type
177 if (PendingMembers.size() > 0)
178 assert(PendingMembers[0].getLocVT() == LocVT)(static_cast<void> (0));
179
180 // Add the argument to the list to be allocated once we know the size of the
181 // aggregate. Store the type's required alignment as extra info for later: in
182 // the [N x i64] case all trace has been removed by the time we actually get
183 // to do allocation.
184 PendingMembers.push_back(CCValAssign::getPending(
185 ValNo, ValVT, LocVT, LocInfo, ArgFlags.getNonZeroOrigAlign().value()));
186
187 if (!ArgFlags.isInConsecutiveRegsLast())
188 return true;
189
190 // Try to allocate a contiguous block of registers, each of the correct
191 // size to hold one member.
192 auto &DL = State.getMachineFunction().getDataLayout();
193 const Align StackAlign = DL.getStackAlignment();
194 const Align FirstMemberAlign(PendingMembers[0].getExtraInfo());
195 Align Alignment = std::min(FirstMemberAlign, StackAlign);
196
197 ArrayRef<MCPhysReg> RegList;
198 switch (LocVT.SimpleTy) {
199 case MVT::i32: {
200 RegList = RRegList;
201 unsigned RegIdx = State.getFirstUnallocated(RegList);
202
203 // First consume all registers that would give an unaligned object. Whether
204 // we go on stack or in regs, no-one will be using them in future.
205 unsigned RegAlign = alignTo(Alignment.value(), 4) / 4;
206 while (RegIdx % RegAlign != 0 && RegIdx < RegList.size())
207 State.AllocateReg(RegList[RegIdx++]);
208
209 break;
210 }
211 case MVT::f16:
212 case MVT::bf16:
213 case MVT::f32:
214 RegList = SRegList;
215 break;
216 case MVT::v4f16:
217 case MVT::v4bf16:
218 case MVT::f64:
219 RegList = DRegList;
220 break;
221 case MVT::v8f16:
222 case MVT::v8bf16:
223 case MVT::v2f64:
224 RegList = QRegList;
225 break;
226 default:
227 llvm_unreachable("Unexpected member type for block aggregate")__builtin_unreachable();
228 break;
229 }
230
231 unsigned RegResult = State.AllocateRegBlock(RegList, PendingMembers.size());
232 if (RegResult) {
233 for (SmallVectorImpl<CCValAssign>::iterator It = PendingMembers.begin();
234 It != PendingMembers.end(); ++It) {
235 It->convertToReg(RegResult);
236 State.addLoc(*It);
237 ++RegResult;
238 }
239 PendingMembers.clear();
240 return true;
241 }
242
243 // Register allocation failed, we'll be needing the stack
244 unsigned Size = LocVT.getSizeInBits() / 8;
245 if (LocVT == MVT::i32 && State.getNextStackOffset() == 0) {
246 // If nothing else has used the stack until this point, a non-HFA aggregate
247 // can be split between regs and stack.
248 unsigned RegIdx = State.getFirstUnallocated(RegList);
249 for (auto &It : PendingMembers) {
250 if (RegIdx >= RegList.size())
251 It.convertToMem(State.AllocateStack(Size, Align(Size)));
252 else
253 It.convertToReg(State.AllocateReg(RegList[RegIdx++]));
254
255 State.addLoc(It);
256 }
257 PendingMembers.clear();
258 return true;
259 }
260
261 if (LocVT != MVT::i32)
262 RegList = SRegList;
263
264 // Mark all regs as unavailable (AAPCS rule C.2.vfp for VFP, C.6 for core)
265 for (auto Reg : RegList)
266 State.AllocateReg(Reg);
267
268 // Clamp the alignment between 4 and 8.
269 if (State.getMachineFunction().getSubtarget<ARMSubtarget>().isTargetAEABI())
270 Alignment = ArgFlags.getNonZeroMemAlign() <= 4 ? Align(4) : Align(8);
271
272 // After the first item has been allocated, the rest are packed as tightly as
273 // possible. (E.g. an incoming i64 would have starting Align of 8, but we'll
274 // be allocating a bunch of i32 slots).
275 for (auto &It : PendingMembers) {
276 It.convertToMem(State.AllocateStack(Size, Alignment));
277 State.addLoc(It);
278 Alignment = Align(1);
279 }
280
281 // All pending members have now been allocated
282 PendingMembers.clear();
283
284 // This will be allocated by the last member of the aggregate
285 return true;
286}
287
288static bool CustomAssignInRegList(unsigned ValNo, MVT ValVT, MVT LocVT,
289 CCValAssign::LocInfo LocInfo, CCState &State,
290 ArrayRef<MCPhysReg> RegList) {
291 unsigned Reg = State.AllocateReg(RegList);
292 if (Reg) {
293 State.addLoc(CCValAssign::getCustomReg(ValNo, ValVT, Reg, LocVT, LocInfo));
294 return true;
295 }
296 return false;
297}
298
299static bool CC_ARM_AAPCS_Custom_f16(unsigned ValNo, MVT ValVT, MVT LocVT,
300 CCValAssign::LocInfo LocInfo,
301 ISD::ArgFlagsTy ArgFlags, CCState &State) {
302 // f16 arguments are extended to i32 and assigned to a register in [r0, r3]
303 return CustomAssignInRegList(ValNo, ValVT, MVT::i32, LocInfo, State,
304 RRegList);
305}
306
307static bool CC_ARM_AAPCS_VFP_Custom_f16(unsigned ValNo, MVT ValVT, MVT LocVT,
308 CCValAssign::LocInfo LocInfo,
309 ISD::ArgFlagsTy ArgFlags,
310 CCState &State) {
311 // f16 arguments are extended to f32 and assigned to a register in [s0, s15]
312 return CustomAssignInRegList(ValNo, ValVT, MVT::f32, LocInfo, State,
313 SRegList);
314}
315
316// Include the table generated calling convention implementations.
317#include "ARMGenCallingConv.inc"