1 //===-- IntrinsicLowering.cpp - Intrinsic Lowering default implementation -===//
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 implements the IntrinsicLowering class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/CodeGen/IntrinsicLowering.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/IR/Constants.h"
16 #include "llvm/IR/DataLayout.h"
17 #include "llvm/IR/DerivedTypes.h"
18 #include "llvm/IR/IRBuilder.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/IR/Type.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/raw_ostream.h"
23 using namespace llvm;
24 
25 /// This function is used when we want to lower an intrinsic call to a call of
26 /// an external function. This handles hard cases such as when there was already
27 /// a prototype for the external function, but that prototype doesn't match the
28 /// arguments we expect to pass in.
29 template <class ArgIt>
ReplaceCallWith(const char * NewFn,CallInst * CI,ArgIt ArgBegin,ArgIt ArgEnd,Type * RetTy)30 static CallInst *ReplaceCallWith(const char *NewFn, CallInst *CI,
31                                  ArgIt ArgBegin, ArgIt ArgEnd,
32                                  Type *RetTy) {
33   // If we haven't already looked up this function, check to see if the
34   // program already contains a function with this name.
35   Module *M = CI->getModule();
36   // Get or insert the definition now.
37   std::vector<Type *> ParamTys;
38   for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
39     ParamTys.push_back((*I)->getType());
40   FunctionCallee FCache =
41       M->getOrInsertFunction(NewFn, FunctionType::get(RetTy, ParamTys, false));
42 
43   IRBuilder<> Builder(CI->getParent(), CI->getIterator());
44   SmallVector<Value *, 8> Args(ArgBegin, ArgEnd);
45   CallInst *NewCI = Builder.CreateCall(FCache, Args);
46   NewCI->setName(CI->getName());
47   if (!CI->use_empty())
48     CI->replaceAllUsesWith(NewCI);
49   return NewCI;
50 }
51 
52 /// Emit the code to lower bswap of V before the specified instruction IP.
LowerBSWAP(LLVMContext & Context,Value * V,Instruction * IP)53 static Value *LowerBSWAP(LLVMContext &Context, Value *V, Instruction *IP) {
54   assert(V->getType()->isIntOrIntVectorTy() && "Can't bswap a non-integer type!");
55 
56   unsigned BitSize = V->getType()->getScalarSizeInBits();
57 
58   IRBuilder<> Builder(IP);
59 
60   switch(BitSize) {
61   default: llvm_unreachable("Unhandled type size of value to byteswap!");
62   case 16: {
63     Value *Tmp1 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
64                                     "bswap.2");
65     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
66                                      "bswap.1");
67     V = Builder.CreateOr(Tmp1, Tmp2, "bswap.i16");
68     break;
69   }
70   case 32: {
71     Value *Tmp4 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
72                                     "bswap.4");
73     Value *Tmp3 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
74                                     "bswap.3");
75     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
76                                      "bswap.2");
77     Value *Tmp1 = Builder.CreateLShr(V,ConstantInt::get(V->getType(), 24),
78                                      "bswap.1");
79     Tmp3 = Builder.CreateAnd(Tmp3,
80                          ConstantInt::get(V->getType(), 0xFF0000),
81                              "bswap.and3");
82     Tmp2 = Builder.CreateAnd(Tmp2,
83                            ConstantInt::get(V->getType(), 0xFF00),
84                              "bswap.and2");
85     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or1");
86     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or2");
87     V = Builder.CreateOr(Tmp4, Tmp2, "bswap.i32");
88     break;
89   }
90   case 64: {
91     Value *Tmp8 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 56),
92                                     "bswap.8");
93     Value *Tmp7 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 40),
94                                     "bswap.7");
95     Value *Tmp6 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
96                                     "bswap.6");
97     Value *Tmp5 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
98                                     "bswap.5");
99     Value* Tmp4 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
100                                      "bswap.4");
101     Value* Tmp3 = Builder.CreateLShr(V,
102                                      ConstantInt::get(V->getType(), 24),
103                                      "bswap.3");
104     Value* Tmp2 = Builder.CreateLShr(V,
105                                      ConstantInt::get(V->getType(), 40),
106                                      "bswap.2");
107     Value* Tmp1 = Builder.CreateLShr(V,
108                                      ConstantInt::get(V->getType(), 56),
109                                      "bswap.1");
110     Tmp7 = Builder.CreateAnd(Tmp7,
111                              ConstantInt::get(V->getType(),
112                                               0xFF000000000000ULL),
113                              "bswap.and7");
114     Tmp6 = Builder.CreateAnd(Tmp6,
115                              ConstantInt::get(V->getType(),
116                                               0xFF0000000000ULL),
117                              "bswap.and6");
118     Tmp5 = Builder.CreateAnd(Tmp5,
119                         ConstantInt::get(V->getType(),
120                              0xFF00000000ULL),
121                              "bswap.and5");
122     Tmp4 = Builder.CreateAnd(Tmp4,
123                         ConstantInt::get(V->getType(),
124                              0xFF000000ULL),
125                              "bswap.and4");
126     Tmp3 = Builder.CreateAnd(Tmp3,
127                              ConstantInt::get(V->getType(),
128                              0xFF0000ULL),
129                              "bswap.and3");
130     Tmp2 = Builder.CreateAnd(Tmp2,
131                              ConstantInt::get(V->getType(),
132                              0xFF00ULL),
133                              "bswap.and2");
134     Tmp8 = Builder.CreateOr(Tmp8, Tmp7, "bswap.or1");
135     Tmp6 = Builder.CreateOr(Tmp6, Tmp5, "bswap.or2");
136     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or3");
137     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or4");
138     Tmp8 = Builder.CreateOr(Tmp8, Tmp6, "bswap.or5");
139     Tmp4 = Builder.CreateOr(Tmp4, Tmp2, "bswap.or6");
140     V = Builder.CreateOr(Tmp8, Tmp4, "bswap.i64");
141     break;
142   }
143   }
144   return V;
145 }
146 
147 /// Emit the code to lower ctpop of V before the specified instruction IP.
LowerCTPOP(LLVMContext & Context,Value * V,Instruction * IP)148 static Value *LowerCTPOP(LLVMContext &Context, Value *V, Instruction *IP) {
149   assert(V->getType()->isIntegerTy() && "Can't ctpop a non-integer type!");
150 
151   static const uint64_t MaskValues[6] = {
152     0x5555555555555555ULL, 0x3333333333333333ULL,
153     0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
154     0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL
155   };
156 
157   IRBuilder<> Builder(IP);
158 
159   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
160   unsigned WordSize = (BitSize + 63) / 64;
161   Value *Count = ConstantInt::get(V->getType(), 0);
162 
163   for (unsigned n = 0; n < WordSize; ++n) {
164     Value *PartValue = V;
165     for (unsigned i = 1, ct = 0; i < (BitSize>64 ? 64 : BitSize);
166          i <<= 1, ++ct) {
167       Value *MaskCst = ConstantInt::get(V->getType(), MaskValues[ct]);
168       Value *LHS = Builder.CreateAnd(PartValue, MaskCst, "cppop.and1");
169       Value *VShift = Builder.CreateLShr(PartValue,
170                                         ConstantInt::get(V->getType(), i),
171                                          "ctpop.sh");
172       Value *RHS = Builder.CreateAnd(VShift, MaskCst, "cppop.and2");
173       PartValue = Builder.CreateAdd(LHS, RHS, "ctpop.step");
174     }
175     Count = Builder.CreateAdd(PartValue, Count, "ctpop.part");
176     if (BitSize > 64) {
177       V = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 64),
178                              "ctpop.part.sh");
179       BitSize -= 64;
180     }
181   }
182 
183   return Count;
184 }
185 
186 /// Emit the code to lower ctlz of V before the specified instruction IP.
LowerCTLZ(LLVMContext & Context,Value * V,Instruction * IP)187 static Value *LowerCTLZ(LLVMContext &Context, Value *V, Instruction *IP) {
188 
189   IRBuilder<> Builder(IP);
190 
191   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
192   for (unsigned i = 1; i < BitSize; i <<= 1) {
193     Value *ShVal = ConstantInt::get(V->getType(), i);
194     ShVal = Builder.CreateLShr(V, ShVal, "ctlz.sh");
195     V = Builder.CreateOr(V, ShVal, "ctlz.step");
196   }
197 
198   V = Builder.CreateNot(V);
199   return LowerCTPOP(Context, V, IP);
200 }
201 
ReplaceFPIntrinsicWithCall(CallInst * CI,const char * Fname,const char * Dname,const char * LDname)202 static void ReplaceFPIntrinsicWithCall(CallInst *CI, const char *Fname,
203                                        const char *Dname,
204                                        const char *LDname) {
205   switch (CI->getArgOperand(0)->getType()->getTypeID()) {
206   default: llvm_unreachable("Invalid type in intrinsic");
207   case Type::FloatTyID:
208     ReplaceCallWith(Fname, CI, CI->arg_begin(), CI->arg_end(),
209                     Type::getFloatTy(CI->getContext()));
210     break;
211   case Type::DoubleTyID:
212     ReplaceCallWith(Dname, CI, CI->arg_begin(), CI->arg_end(),
213                     Type::getDoubleTy(CI->getContext()));
214     break;
215   case Type::X86_FP80TyID:
216   case Type::FP128TyID:
217   case Type::PPC_FP128TyID:
218     ReplaceCallWith(LDname, CI, CI->arg_begin(), CI->arg_end(),
219                     CI->getArgOperand(0)->getType());
220     break;
221   }
222 }
223 
LowerIntrinsicCall(CallInst * CI)224 void IntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
225   IRBuilder<> Builder(CI);
226   LLVMContext &Context = CI->getContext();
227 
228   const Function *Callee = CI->getCalledFunction();
229   assert(Callee && "Cannot lower an indirect call!");
230 
231   switch (Callee->getIntrinsicID()) {
232   case Intrinsic::not_intrinsic:
233     report_fatal_error("Cannot lower a call to a non-intrinsic function '"+
234                       Callee->getName() + "'!");
235   default:
236     report_fatal_error("Code generator does not support intrinsic function '"+
237                       Callee->getName()+"'!");
238 
239   case Intrinsic::expect: {
240     // Just replace __builtin_expect(exp, c) with EXP.
241     Value *V = CI->getArgOperand(0);
242     CI->replaceAllUsesWith(V);
243     break;
244   }
245 
246   case Intrinsic::ctpop:
247     CI->replaceAllUsesWith(LowerCTPOP(Context, CI->getArgOperand(0), CI));
248     break;
249 
250   case Intrinsic::bswap:
251     CI->replaceAllUsesWith(LowerBSWAP(Context, CI->getArgOperand(0), CI));
252     break;
253 
254   case Intrinsic::ctlz:
255     CI->replaceAllUsesWith(LowerCTLZ(Context, CI->getArgOperand(0), CI));
256     break;
257 
258   case Intrinsic::cttz: {
259     // cttz(x) -> ctpop(~X & (X-1))
260     Value *Src = CI->getArgOperand(0);
261     Value *NotSrc = Builder.CreateNot(Src);
262     NotSrc->setName(Src->getName() + ".not");
263     Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
264     SrcM1 = Builder.CreateSub(Src, SrcM1);
265     Src = LowerCTPOP(Context, Builder.CreateAnd(NotSrc, SrcM1), CI);
266     CI->replaceAllUsesWith(Src);
267     break;
268   }
269 
270   case Intrinsic::stacksave:
271   case Intrinsic::stackrestore: {
272     if (!Warned)
273       errs() << "WARNING: this target does not support the llvm.stack"
274              << (Callee->getIntrinsicID() == Intrinsic::stacksave ?
275                "save" : "restore") << " intrinsic.\n";
276     Warned = true;
277     if (Callee->getIntrinsicID() == Intrinsic::stacksave)
278       CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
279     break;
280   }
281 
282   case Intrinsic::get_dynamic_area_offset:
283     errs() << "WARNING: this target does not support the custom llvm.get."
284               "dynamic.area.offset.  It is being lowered to a constant 0\n";
285     // Just lower it to a constant 0 because for most targets
286     // @llvm.get.dynamic.area.offset is lowered to zero.
287     CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 0));
288     break;
289   case Intrinsic::returnaddress:
290   case Intrinsic::frameaddress:
291     errs() << "WARNING: this target does not support the llvm."
292            << (Callee->getIntrinsicID() == Intrinsic::returnaddress ?
293              "return" : "frame") << "address intrinsic.\n";
294     CI->replaceAllUsesWith(
295         ConstantPointerNull::get(cast<PointerType>(CI->getType())));
296     break;
297   case Intrinsic::addressofreturnaddress:
298     errs() << "WARNING: this target does not support the "
299               "llvm.addressofreturnaddress intrinsic.\n";
300     CI->replaceAllUsesWith(
301         ConstantPointerNull::get(cast<PointerType>(CI->getType())));
302     break;
303 
304   case Intrinsic::prefetch:
305     break;    // Simply strip out prefetches on unsupported architectures
306 
307   case Intrinsic::pcmarker:
308     break;    // Simply strip out pcmarker on unsupported architectures
309   case Intrinsic::readcyclecounter: {
310     errs() << "WARNING: this target does not support the llvm.readcyclecoun"
311            << "ter intrinsic.  It is being lowered to a constant 0\n";
312     CI->replaceAllUsesWith(ConstantInt::get(Type::getInt64Ty(Context), 0));
313     break;
314   }
315 
316   case Intrinsic::dbg_declare:
317   case Intrinsic::dbg_label:
318     break;    // Simply strip out debugging intrinsics
319 
320   case Intrinsic::eh_typeid_for:
321     // Return something different to eh_selector.
322     CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
323     break;
324 
325   case Intrinsic::annotation:
326   case Intrinsic::ptr_annotation:
327     // Just drop the annotation, but forward the value
328     CI->replaceAllUsesWith(CI->getOperand(0));
329     break;
330 
331   case Intrinsic::assume:
332   case Intrinsic::var_annotation:
333     break;   // Strip out these intrinsics
334 
335   case Intrinsic::memcpy: {
336     Type *IntPtr = DL.getIntPtrType(Context);
337     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
338                                         /* isSigned */ false);
339     Value *Ops[3];
340     Ops[0] = CI->getArgOperand(0);
341     Ops[1] = CI->getArgOperand(1);
342     Ops[2] = Size;
343     ReplaceCallWith("memcpy", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
344     break;
345   }
346   case Intrinsic::memmove: {
347     Type *IntPtr = DL.getIntPtrType(Context);
348     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
349                                         /* isSigned */ false);
350     Value *Ops[3];
351     Ops[0] = CI->getArgOperand(0);
352     Ops[1] = CI->getArgOperand(1);
353     Ops[2] = Size;
354     ReplaceCallWith("memmove", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
355     break;
356   }
357   case Intrinsic::memset: {
358     Value *Op0 = CI->getArgOperand(0);
359     Type *IntPtr = DL.getIntPtrType(Op0->getType());
360     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
361                                         /* isSigned */ false);
362     Value *Ops[3];
363     Ops[0] = Op0;
364     // Extend the amount to i32.
365     Ops[1] = Builder.CreateIntCast(CI->getArgOperand(1),
366                                    Type::getInt32Ty(Context),
367                                    /* isSigned */ false);
368     Ops[2] = Size;
369     ReplaceCallWith("memset", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
370     break;
371   }
372   case Intrinsic::sqrt: {
373     ReplaceFPIntrinsicWithCall(CI, "sqrtf", "sqrt", "sqrtl");
374     break;
375   }
376   case Intrinsic::log: {
377     ReplaceFPIntrinsicWithCall(CI, "logf", "log", "logl");
378     break;
379   }
380   case Intrinsic::log2: {
381     ReplaceFPIntrinsicWithCall(CI, "log2f", "log2", "log2l");
382     break;
383   }
384   case Intrinsic::log10: {
385     ReplaceFPIntrinsicWithCall(CI, "log10f", "log10", "log10l");
386     break;
387   }
388   case Intrinsic::exp: {
389     ReplaceFPIntrinsicWithCall(CI, "expf", "exp", "expl");
390     break;
391   }
392   case Intrinsic::exp2: {
393     ReplaceFPIntrinsicWithCall(CI, "exp2f", "exp2", "exp2l");
394     break;
395   }
396   case Intrinsic::pow: {
397     ReplaceFPIntrinsicWithCall(CI, "powf", "pow", "powl");
398     break;
399   }
400   case Intrinsic::sin: {
401     ReplaceFPIntrinsicWithCall(CI, "sinf", "sin", "sinl");
402     break;
403   }
404   case Intrinsic::cos: {
405     ReplaceFPIntrinsicWithCall(CI, "cosf", "cos", "cosl");
406     break;
407   }
408   case Intrinsic::floor: {
409     ReplaceFPIntrinsicWithCall(CI, "floorf", "floor", "floorl");
410     break;
411   }
412   case Intrinsic::ceil: {
413     ReplaceFPIntrinsicWithCall(CI, "ceilf", "ceil", "ceill");
414     break;
415   }
416   case Intrinsic::trunc: {
417     ReplaceFPIntrinsicWithCall(CI, "truncf", "trunc", "truncl");
418     break;
419   }
420   case Intrinsic::round: {
421     ReplaceFPIntrinsicWithCall(CI, "roundf", "round", "roundl");
422     break;
423   }
424   case Intrinsic::roundeven: {
425     ReplaceFPIntrinsicWithCall(CI, "roundevenf", "roundeven", "roundevenl");
426     break;
427   }
428   case Intrinsic::copysign: {
429     ReplaceFPIntrinsicWithCall(CI, "copysignf", "copysign", "copysignl");
430     break;
431   }
432   case Intrinsic::flt_rounds:
433      // Lower to "round to the nearest"
434      if (!CI->getType()->isVoidTy())
435        CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
436      break;
437   case Intrinsic::invariant_start:
438   case Intrinsic::lifetime_start:
439     // Discard region information.
440     CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
441     break;
442   case Intrinsic::invariant_end:
443   case Intrinsic::lifetime_end:
444     // Discard region information.
445     break;
446   }
447 
448   assert(CI->use_empty() &&
449          "Lowering should have eliminated any uses of the intrinsic call!");
450   CI->eraseFromParent();
451 }
452 
LowerToByteSwap(CallInst * CI)453 bool IntrinsicLowering::LowerToByteSwap(CallInst *CI) {
454   // Verify this is a simple bswap.
455   if (CI->getNumArgOperands() != 1 ||
456       CI->getType() != CI->getArgOperand(0)->getType() ||
457       !CI->getType()->isIntegerTy())
458     return false;
459 
460   IntegerType *Ty = dyn_cast<IntegerType>(CI->getType());
461   if (!Ty)
462     return false;
463 
464   // Okay, we can do this xform, do so now.
465   Module *M = CI->getModule();
466   Function *Int = Intrinsic::getDeclaration(M, Intrinsic::bswap, Ty);
467 
468   Value *Op = CI->getArgOperand(0);
469   Op = CallInst::Create(Int, Op, CI->getName(), CI);
470 
471   CI->replaceAllUsesWith(Op);
472   CI->eraseFromParent();
473   return true;
474 }
475