1 //===-- X86ShuffleDecode.cpp - X86 shuffle decode logic -------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Define several functions to decode x86 specific shuffle semantics into a
11 // generic vector mask.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "X86ShuffleDecode.h"
16 #include "llvm/IR/Constants.h"
17 #include "llvm/CodeGen/MachineValueType.h"
18 
19 //===----------------------------------------------------------------------===//
20 //  Vector Mask Decoding
21 //===----------------------------------------------------------------------===//
22 
23 namespace llvm {
24 
25 void DecodeINSERTPSMask(unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
26   // Defaults the copying the dest value.
27   ShuffleMask.push_back(0);
28   ShuffleMask.push_back(1);
29   ShuffleMask.push_back(2);
30   ShuffleMask.push_back(3);
31 
32   // Decode the immediate.
33   unsigned ZMask = Imm & 15;
34   unsigned CountD = (Imm >> 4) & 3;
35   unsigned CountS = (Imm >> 6) & 3;
36 
37   // CountS selects which input element to use.
38   unsigned InVal = 4+CountS;
39   // CountD specifies which element of destination to update.
40   ShuffleMask[CountD] = InVal;
41   // ZMask zaps values, potentially overriding the CountD elt.
42   if (ZMask & 1) ShuffleMask[0] = SM_SentinelZero;
43   if (ZMask & 2) ShuffleMask[1] = SM_SentinelZero;
44   if (ZMask & 4) ShuffleMask[2] = SM_SentinelZero;
45   if (ZMask & 8) ShuffleMask[3] = SM_SentinelZero;
46 }
47 
48 // <3,1> or <6,7,2,3>
49 void DecodeMOVHLPSMask(unsigned NElts, SmallVectorImpl<int> &ShuffleMask) {
50   for (unsigned i = NElts/2; i != NElts; ++i)
51     ShuffleMask.push_back(NElts+i);
52 
53   for (unsigned i = NElts/2; i != NElts; ++i)
54     ShuffleMask.push_back(i);
55 }
56 
57 // <0,2> or <0,1,4,5>
58 void DecodeMOVLHPSMask(unsigned NElts, SmallVectorImpl<int> &ShuffleMask) {
59   for (unsigned i = 0; i != NElts/2; ++i)
60     ShuffleMask.push_back(i);
61 
62   for (unsigned i = 0; i != NElts/2; ++i)
63     ShuffleMask.push_back(NElts+i);
64 }
65 
66 void DecodeMOVSLDUPMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
67   unsigned NumElts = VT.getVectorNumElements();
68   for (int i = 0, e = NumElts / 2; i < e; ++i) {
69     ShuffleMask.push_back(2 * i);
70     ShuffleMask.push_back(2 * i);
71   }
72 }
73 
74 void DecodeMOVSHDUPMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
75   unsigned NumElts = VT.getVectorNumElements();
76   for (int i = 0, e = NumElts / 2; i < e; ++i) {
77     ShuffleMask.push_back(2 * i + 1);
78     ShuffleMask.push_back(2 * i + 1);
79   }
80 }
81 
82 void DecodePSLLDQMask(MVT VT, unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
83   unsigned VectorSizeInBits = VT.getSizeInBits();
84   unsigned NumElts = VectorSizeInBits / 8;
85   unsigned NumLanes = VectorSizeInBits / 128;
86   unsigned NumLaneElts = NumElts / NumLanes;
87 
88   for (unsigned l = 0; l < NumElts; l += NumLaneElts)
89     for (unsigned i = 0; i < NumLaneElts; ++i) {
90       int M = SM_SentinelZero;
91       if (i >= Imm) M = i - Imm + l;
92       ShuffleMask.push_back(M);
93     }
94 }
95 
96 void DecodePSRLDQMask(MVT VT, unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
97   unsigned VectorSizeInBits = VT.getSizeInBits();
98   unsigned NumElts = VectorSizeInBits / 8;
99   unsigned NumLanes = VectorSizeInBits / 128;
100   unsigned NumLaneElts = NumElts / NumLanes;
101 
102   for (unsigned l = 0; l < NumElts; l += NumLaneElts)
103     for (unsigned i = 0; i < NumLaneElts; ++i) {
104       unsigned Base = i + Imm;
105       int M = Base + l;
106       if (Base >= NumLaneElts) M = SM_SentinelZero;
107       ShuffleMask.push_back(M);
108     }
109 }
110 
111 void DecodePALIGNRMask(MVT VT, unsigned Imm,
112                        SmallVectorImpl<int> &ShuffleMask) {
113   unsigned NumElts = VT.getVectorNumElements();
114   unsigned Offset = Imm * (VT.getVectorElementType().getSizeInBits() / 8);
115 
116   unsigned NumLanes = VT.getSizeInBits() / 128;
117   unsigned NumLaneElts = NumElts / NumLanes;
118 
119   for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
120     for (unsigned i = 0; i != NumLaneElts; ++i) {
121       unsigned Base = i + Offset;
122       // if i+offset is out of this lane then we actually need the other source
123       if (Base >= NumLaneElts) Base += NumElts - NumLaneElts;
124       ShuffleMask.push_back(Base + l);
125     }
126   }
127 }
128 
129 /// DecodePSHUFMask - This decodes the shuffle masks for pshufd, and vpermilp*.
130 /// VT indicates the type of the vector allowing it to handle different
131 /// datatypes and vector widths.
132 void DecodePSHUFMask(MVT VT, unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
133   unsigned NumElts = VT.getVectorNumElements();
134 
135   unsigned NumLanes = VT.getSizeInBits() / 128;
136   unsigned NumLaneElts = NumElts / NumLanes;
137 
138   unsigned NewImm = Imm;
139   for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
140     for (unsigned i = 0; i != NumLaneElts; ++i) {
141       ShuffleMask.push_back(NewImm % NumLaneElts + l);
142       NewImm /= NumLaneElts;
143     }
144     if (NumLaneElts == 4) NewImm = Imm; // reload imm
145   }
146 }
147 
148 void DecodePSHUFHWMask(MVT VT, unsigned Imm,
149                        SmallVectorImpl<int> &ShuffleMask) {
150   unsigned NumElts = VT.getVectorNumElements();
151 
152   for (unsigned l = 0; l != NumElts; l += 8) {
153     unsigned NewImm = Imm;
154     for (unsigned i = 0, e = 4; i != e; ++i) {
155       ShuffleMask.push_back(l + i);
156     }
157     for (unsigned i = 4, e = 8; i != e; ++i) {
158       ShuffleMask.push_back(l + 4 + (NewImm & 3));
159       NewImm >>= 2;
160     }
161   }
162 }
163 
164 void DecodePSHUFLWMask(MVT VT, unsigned Imm,
165                        SmallVectorImpl<int> &ShuffleMask) {
166   unsigned NumElts = VT.getVectorNumElements();
167 
168   for (unsigned l = 0; l != NumElts; l += 8) {
169     unsigned NewImm = Imm;
170     for (unsigned i = 0, e = 4; i != e; ++i) {
171       ShuffleMask.push_back(l + (NewImm & 3));
172       NewImm >>= 2;
173     }
174     for (unsigned i = 4, e = 8; i != e; ++i) {
175       ShuffleMask.push_back(l + i);
176     }
177   }
178 }
179 
180 /// DecodeSHUFPMask - This decodes the shuffle masks for shufp*. VT indicates
181 /// the type of the vector allowing it to handle different datatypes and vector
182 /// widths.
183 void DecodeSHUFPMask(MVT VT, unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
184   unsigned NumElts = VT.getVectorNumElements();
185 
186   unsigned NumLanes = VT.getSizeInBits() / 128;
187   unsigned NumLaneElts = NumElts / NumLanes;
188 
189   unsigned NewImm = Imm;
190   for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
191     // each half of a lane comes from different source
192     for (unsigned s = 0; s != NumElts*2; s += NumElts) {
193       for (unsigned i = 0; i != NumLaneElts/2; ++i) {
194         ShuffleMask.push_back(NewImm % NumLaneElts + s + l);
195         NewImm /= NumLaneElts;
196       }
197     }
198     if (NumLaneElts == 4) NewImm = Imm; // reload imm
199   }
200 }
201 
202 /// DecodeUNPCKHMask - This decodes the shuffle masks for unpckhps/unpckhpd
203 /// and punpckh*. VT indicates the type of the vector allowing it to handle
204 /// different datatypes and vector widths.
205 void DecodeUNPCKHMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
206   unsigned NumElts = VT.getVectorNumElements();
207 
208   // Handle 128 and 256-bit vector lengths. AVX defines UNPCK* to operate
209   // independently on 128-bit lanes.
210   unsigned NumLanes = VT.getSizeInBits() / 128;
211   if (NumLanes == 0 ) NumLanes = 1;  // Handle MMX
212   unsigned NumLaneElts = NumElts / NumLanes;
213 
214   for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
215     for (unsigned i = l + NumLaneElts/2, e = l + NumLaneElts; i != e; ++i) {
216       ShuffleMask.push_back(i);          // Reads from dest/src1
217       ShuffleMask.push_back(i+NumElts);  // Reads from src/src2
218     }
219   }
220 }
221 
222 /// DecodeUNPCKLMask - This decodes the shuffle masks for unpcklps/unpcklpd
223 /// and punpckl*. VT indicates the type of the vector allowing it to handle
224 /// different datatypes and vector widths.
225 void DecodeUNPCKLMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
226   unsigned NumElts = VT.getVectorNumElements();
227 
228   // Handle 128 and 256-bit vector lengths. AVX defines UNPCK* to operate
229   // independently on 128-bit lanes.
230   unsigned NumLanes = VT.getSizeInBits() / 128;
231   if (NumLanes == 0 ) NumLanes = 1;  // Handle MMX
232   unsigned NumLaneElts = NumElts / NumLanes;
233 
234   for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
235     for (unsigned i = l, e = l + NumLaneElts/2; i != e; ++i) {
236       ShuffleMask.push_back(i);          // Reads from dest/src1
237       ShuffleMask.push_back(i+NumElts);  // Reads from src/src2
238     }
239   }
240 }
241 
242 void DecodeVPERM2X128Mask(MVT VT, unsigned Imm,
243                           SmallVectorImpl<int> &ShuffleMask) {
244   if (Imm & 0x88)
245     return; // Not a shuffle
246 
247   unsigned HalfSize = VT.getVectorNumElements()/2;
248 
249   for (unsigned l = 0; l != 2; ++l) {
250     unsigned HalfBegin = ((Imm >> (l*4)) & 0x3) * HalfSize;
251     for (unsigned i = HalfBegin, e = HalfBegin+HalfSize; i != e; ++i)
252       ShuffleMask.push_back(i);
253   }
254 }
255 
256 void DecodePSHUFBMask(const Constant *C, SmallVectorImpl<int> &ShuffleMask) {
257   Type *MaskTy = C->getType();
258   // It is not an error for the PSHUFB mask to not be a vector of i8 because the
259   // constant pool uniques constants by their bit representation.
260   // e.g. the following take up the same space in the constant pool:
261   //   i128 -170141183420855150465331762880109871104
262   //
263   //   <2 x i64> <i64 -9223372034707292160, i64 -9223372034707292160>
264   //
265   //   <4 x i32> <i32 -2147483648, i32 -2147483648,
266   //              i32 -2147483648, i32 -2147483648>
267 
268   unsigned MaskTySize = MaskTy->getPrimitiveSizeInBits();
269 
270   if (MaskTySize != 128 && MaskTySize != 256) // FIXME: Add support for AVX-512.
271     return;
272 
273   // This is a straightforward byte vector.
274   if (MaskTy->isVectorTy() && MaskTy->getVectorElementType()->isIntegerTy(8)) {
275     int NumElements = MaskTy->getVectorNumElements();
276     ShuffleMask.reserve(NumElements);
277 
278     for (int i = 0; i < NumElements; ++i) {
279       // For AVX vectors with 32 bytes the base of the shuffle is the 16-byte
280       // lane of the vector we're inside.
281       int Base = i < 16 ? 0 : 16;
282       Constant *COp = C->getAggregateElement(i);
283       if (!COp) {
284         ShuffleMask.clear();
285         return;
286       } else if (isa<UndefValue>(COp)) {
287         ShuffleMask.push_back(SM_SentinelUndef);
288         continue;
289       }
290       uint64_t Element = cast<ConstantInt>(COp)->getZExtValue();
291       // If the high bit (7) of the byte is set, the element is zeroed.
292       if (Element & (1 << 7))
293         ShuffleMask.push_back(SM_SentinelZero);
294       else {
295         // Only the least significant 4 bits of the byte are used.
296         int Index = Base + (Element & 0xf);
297         ShuffleMask.push_back(Index);
298       }
299     }
300   }
301   // TODO: Handle funny-looking vectors too.
302 }
303 
304 void DecodePSHUFBMask(ArrayRef<uint64_t> RawMask,
305                       SmallVectorImpl<int> &ShuffleMask) {
306   for (int i = 0, e = RawMask.size(); i < e; ++i) {
307     uint64_t M = RawMask[i];
308     if (M == (uint64_t)SM_SentinelUndef) {
309       ShuffleMask.push_back(M);
310       continue;
311     }
312     // For AVX vectors with 32 bytes the base of the shuffle is the half of
313     // the vector we're inside.
314     int Base = i < 16 ? 0 : 16;
315     // If the high bit (7) of the byte is set, the element is zeroed.
316     if (M & (1 << 7))
317       ShuffleMask.push_back(SM_SentinelZero);
318     else {
319       // Only the least significant 4 bits of the byte are used.
320       int Index = Base + (M & 0xf);
321       ShuffleMask.push_back(Index);
322     }
323   }
324 }
325 
326 void DecodeBLENDMask(MVT VT, unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
327   int ElementBits = VT.getScalarSizeInBits();
328   int NumElements = VT.getVectorNumElements();
329   for (int i = 0; i < NumElements; ++i) {
330     // If there are more than 8 elements in the vector, then any immediate blend
331     // mask applies to each 128-bit lane. There can never be more than
332     // 8 elements in a 128-bit lane with an immediate blend.
333     int Bit = NumElements > 8 ? i % (128 / ElementBits) : i;
334     assert(Bit < 8 &&
335            "Immediate blends only operate over 8 elements at a time!");
336     ShuffleMask.push_back(((Imm >> Bit) & 1) ? NumElements + i : i);
337   }
338 }
339 
340 /// DecodeVPERMMask - this decodes the shuffle masks for VPERMQ/VPERMPD.
341 /// No VT provided since it only works on 256-bit, 4 element vectors.
342 void DecodeVPERMMask(unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
343   for (unsigned i = 0; i != 4; ++i) {
344     ShuffleMask.push_back((Imm >> (2*i)) & 3);
345   }
346 }
347 
348 void DecodeVPERMILPMask(const Constant *C, SmallVectorImpl<int> &ShuffleMask) {
349   Type *MaskTy = C->getType();
350   assert(MaskTy->isVectorTy() && "Expected a vector constant mask!");
351   assert(MaskTy->getVectorElementType()->isIntegerTy() &&
352          "Expected integer constant mask elements!");
353   int ElementBits = MaskTy->getScalarSizeInBits();
354   int NumElements = MaskTy->getVectorNumElements();
355   assert((NumElements == 2 || NumElements == 4 || NumElements == 8) &&
356          "Unexpected number of vector elements.");
357   ShuffleMask.reserve(NumElements);
358   if (auto *CDS = dyn_cast<ConstantDataSequential>(C)) {
359     assert((unsigned)NumElements == CDS->getNumElements() &&
360            "Constant mask has a different number of elements!");
361 
362     for (int i = 0; i < NumElements; ++i) {
363       int Base = (i * ElementBits / 128) * (128 / ElementBits);
364       uint64_t Element = CDS->getElementAsInteger(i);
365       // Only the least significant 2 bits of the integer are used.
366       int Index = Base + (Element & 0x3);
367       ShuffleMask.push_back(Index);
368     }
369   } else if (auto *CV = dyn_cast<ConstantVector>(C)) {
370     assert((unsigned)NumElements == C->getNumOperands() &&
371            "Constant mask has a different number of elements!");
372 
373     for (int i = 0; i < NumElements; ++i) {
374       int Base = (i * ElementBits / 128) * (128 / ElementBits);
375       Constant *COp = CV->getOperand(i);
376       if (isa<UndefValue>(COp)) {
377         ShuffleMask.push_back(SM_SentinelUndef);
378         continue;
379       }
380       uint64_t Element = cast<ConstantInt>(COp)->getZExtValue();
381       // Only the least significant 2 bits of the integer are used.
382       int Index = Base + (Element & 0x3);
383       ShuffleMask.push_back(Index);
384     }
385   }
386 }
387 
388 } // llvm namespace
389