Use poison instead of undef values wherever possible (#2960)

In reverse translation always use poison values except cases where we translate OpUndef. In other cases common sense was used to define where it is safe to replace undef to poison (e.g. in creating structures, regularization passes).

This resolves #2953 and aligns us with the LLVM community in terms of generating IR.

Author: vmaksimo

docs/SPIRVRepresentationInLLVM.rst

@@ -261,7 +261,7 @@ scalar component is mapped to a function call with index argument, i.e.:
 
   ; However SPIRV-LLVM translator will transform it to the following pattern:
   %1 = call spir_func i64 @_Z33__spirv_BuiltInGlobalInvocationIdi(i32 0)
-  %2 = insertelement <3 x i64> undef, i64 %1, i32 0
+  %2 = insertelement <3 x i64> poison, i64 %1, i32 0
   %3 = call spir_func i64 @_Z33__spirv_BuiltInGlobalInvocationIdi(i32 1)
   %4 = insertelement <3 x i64> %2, i64 %3, i32 1
   %5 = call spir_func i64 @_Z33__spirv_BuiltInGlobalInvocationIdi(i32 2)

lib/SPIRV/LLVMSaddWithOverflow.h

@@ -162,7 +162,7 @@ if.then:                                          ; preds = %entry
 if.end21:                                         ; preds = %if.then, %entry
   %overflow = phi i1 [ 0, %entry ], [ %or.cond40, %if.then ]
   %add24 = add i16 %b, %a
-  %agg = insertvalue {i16, i1} undef, i16 %add24, 0
+  %agg = insertvalue {i16, i1} poison, i16 %add24, 0
   %res = insertvalue {i16, i1} %agg, i1 %overflow, 1
   ret {i16, i1} %res
 }
@@ -202,7 +202,7 @@ if.then12:                                        ; preds = %land.lhs.true, %if.
 if.end23:                                         ; preds = %if.then12, %if.else, %land.lhs.true
   %overflow = phi i1 [ 1, %land.lhs.true ], [ 0, %if.else ], [ %or.cond43, %if.then12 ]
   %add24 = add nsw i32 %b, %a
-  %agg = insertvalue {i32, i1} undef, i32 %add24, 0
+  %agg = insertvalue {i32, i1} poison, i32 %add24, 0
   %res = insertvalue {i32, i1} %agg, i1 %overflow, 1
   ret {i32, i1} %res
 }
@@ -242,7 +242,7 @@ if.then12:                                        ; preds = %land.lhs.true, %if.
 if.end23:                                         ; preds = %if.then12, %if.else, %land.lhs.true
   %overflow = phi i1 [ 1, %land.lhs.true ], [ 0, %if.else ], [ %or.cond42, %if.then12 ]
   %add24 = add nsw i64 %b, %a
-  %agg = insertvalue {i64, i1} undef, i64 %add24, 0
+  %agg = insertvalue {i64, i1} poison, i64 %add24, 0
   %res = insertvalue {i64, i1} %agg, i1 %overflow, 1
   ret {i64, i1} %res
 }

lib/SPIRV/LLVMToSPIRVDbgTran.cpp

@@ -161,7 +161,7 @@ void LLVMToSPIRVDbgTran::finalizeDebugValue(
   DIExpression *Expr = DbgValue->getExpression();
   if (!isNonSemanticDebugInfo()) {
     if (DbgValue->getNumVariableLocationOps() > 1) {
-      Val = UndefValue::get(Val->getType());
+      Val = PoisonValue::get(Val->getType());
       Expr = DIExpression::get(M->getContext(), {});
     }
   }

lib/SPIRV/OCLToSPIRV.cpp

@@ -1065,7 +1065,7 @@ void OCLToSPIRVBase::visitCallGetImageSize(CallInst *CI,
           } else if (Desc.Dim == Dim2D && Desc.Arrayed) {
             Constant *Index[] = {getInt32(M, 0), getInt32(M, 1)};
             Constant *Mask = ConstantVector::get(Index);
-            return new ShuffleVectorInst(NCI, UndefValue::get(NCI->getType()),
+            return new ShuffleVectorInst(NCI, PoisonValue::get(NCI->getType()),
                                          Mask, NCI->getName(),
                                          CI->getIterator());
           }
@@ -1410,9 +1410,9 @@ void OCLToSPIRVBase::visitCallScalToVec(CallInst *CI, StringRef MangledName,
   for (auto I : ScalarPos)
     Mutator.mapArg(I, [&](Value *V) {
       Instruction *Inst = InsertElementInst::Create(
-          UndefValue::get(VecTy), V, getInt32(M, 0), "", CI->getIterator());
+          PoisonValue::get(VecTy), V, getInt32(M, 0), "", CI->getIterator());
       return new ShuffleVectorInst(
-          Inst, UndefValue::get(VecTy),
+          Inst, PoisonValue::get(VecTy),
           ConstantVector::getSplat(VecElemCount, getInt32(M, 0)), "",
           CI->getIterator());
     });

lib/SPIRV/SPIRVLowerBitCastToNonStandardType.cpp

@@ -65,7 +65,7 @@ static Value *removeBitCasts(Value *OldValue, Type *NewTy, NFIRBuilder &Builder,
     // If there's only one use, don't create a bitcast for any uses, since it
     // will be immediately replaced anyways.
     if (OldValue->hasOneUse()) {
-      OldValue->replaceAllUsesWith(UndefValue::get(OldValue->getType()));
+      OldValue->replaceAllUsesWith(PoisonValue::get(OldValue->getType()));
     } else {
       OldValue->replaceAllUsesWith(
           Builder.CreateBitCast(NewValue, OldValue->getType()));
@@ -95,7 +95,7 @@ static Value *removeBitCasts(Value *OldValue, Type *NewTy, NFIRBuilder &Builder,
   if (auto *BC = dyn_cast<BitCastInst>(OldValue)) {
     if (BC->getSrcTy() == NewTy) {
       if (BC->hasOneUse()) {
-        BC->replaceAllUsesWith(UndefValue::get(BC->getType()));
+        BC->replaceAllUsesWith(PoisonValue::get(BC->getType()));
         InstsToErase.push_back(BC);
       }
       return BC->getOperand(0);

lib/SPIRV/SPIRVReader.cpp

@@ -1669,7 +1669,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     Constant *Initializer = nullptr;
     if (IsVectorCompute) {
       AddrSpace = VectorComputeUtil::getVCGlobalVarAddressSpace(BS);
-      Initializer = UndefValue::get(Ty);
+      Initializer = PoisonValue::get(Ty);
     } else
       AddrSpace = SPIRSPIRVAddrSpaceMap::rmap(BS);
     // Force SPIRV BuiltIn variable's name to be __spirv_BuiltInXXXX.
@@ -1688,7 +1688,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
       Initializer = Constant::getNullValue(Ty);
     else if (BS == SPIRVStorageClassKind::StorageClassWorkgroup &&
              LinkageTy != GlobalValue::ExternalLinkage)
-      Initializer = dyn_cast<Constant>(UndefValue::get(Ty));
+      Initializer = dyn_cast<Constant>(PoisonValue::get(Ty));
     else if ((LinkageTy != GlobalValue::ExternalLinkage) &&
              (BS == SPIRVStorageClassKind::StorageClassCrossWorkgroup))
       Initializer = Constant::getNullValue(Ty);
@@ -2021,7 +2021,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     for (unsigned Idx = 0; Idx != N; ++Idx) {
       Value *S = Builder.CreateExtractElement(Vec, Builder.getInt32(Idx));
       Value *Lhs = Builder.CreateVectorSplat(M, S);
-      Value *Rhs = UndefValue::get(VTy);
+      Value *Rhs = PoisonValue::get(VTy);
       for (unsigned Idx2 = 0; Idx2 != M; ++Idx2) {
         Value *Vx = Builder.CreateExtractValue(Mat, Idx2);
         Value *Vxi = Builder.CreateExtractElement(Vx, Builder.getInt32(Idx));
@@ -2046,7 +2046,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
         Builder.CreateVectorSplat(VecSize, Scalar, Scalar->getName());
     NewVec->takeName(Scalar);
 
-    Value *V = UndefValue::get(Matrix->getType());
+    Value *V = PoisonValue::get(Matrix->getType());
     for (uint64_t Idx = 0; Idx != ColNum; Idx++) {
       auto *Col = Builder.CreateExtractValue(Matrix, Idx);
       auto *I = Builder.CreateFMul(Col, NewVec);
@@ -2148,7 +2148,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     auto *VTy = FixedVectorType::get(ETy, R1);
     auto *ResultTy = ArrayType::get(VTy, C2);
 
-    Value *Res = UndefValue::get(ResultTy);
+    Value *Res = PoisonValue::get(ResultTy);
 
     for (unsigned Idx = 0; Idx != C2; ++Idx) {
       Value *U = Builder.CreateExtractValue(M2, Idx);
@@ -2181,7 +2181,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
 
     auto *VTy = FixedVectorType::get(ColTy->getElementType(), ColNum);
     auto *ResultTy = ArrayType::get(VTy, RowNum);
-    Value *V = UndefValue::get(ResultTy);
+    Value *V = PoisonValue::get(ResultTy);
 
     SmallVector<Value *, 16> MCache;
     MCache.reserve(ColNum);
@@ -2221,7 +2221,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
 
     // Slowpath
     for (unsigned Idx = 0; Idx != RowNum; ++Idx) {
-      Value *Vec = UndefValue::get(VTy);
+      Value *Vec = PoisonValue::get(VTy);
 
       for (unsigned Idx2 = 0; Idx2 != ColNum; ++Idx2) {
         Value *S =
@@ -2501,7 +2501,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     IntegerType *Int32Ty = IntegerType::get(*Context, 32);
     for (auto I : VS->getComponents()) {
       if (I == static_cast<SPIRVWord>(-1))
-        Components.push_back(UndefValue::get(Int32Ty));
+        Components.push_back(PoisonValue::get(Int32Ty));
       else
         Components.push_back(ConstantInt::get(Int32Ty, I));
     }
@@ -2776,7 +2776,7 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
       CarryInt = Builder.CreateZExt(Carry, Result->getType());
     }
     auto *ResultStruct =
-        Builder.CreateInsertValue(UndefValue::get(StructType::get(
+        Builder.CreateInsertValue(PoisonValue::get(StructType::get(
                                       Result->getType(), CarryInt->getType())),
                                   Result, 0);
     ResultStruct = Builder.CreateInsertValue(ResultStruct, CarryInt, 1);
@@ -2808,8 +2808,8 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     PointerType *Int8PtrTyPrivate = PointerType::get(*Context, SPIRAS_Private);
     IntegerType *Int32Ty = Type::getInt32Ty(*Context);
 
-    Value *UndefInt8Ptr = UndefValue::get(Int8PtrTyPrivate);
-    Value *UndefInt32 = UndefValue::get(Int32Ty);
+    Value *UndefInt8Ptr = PoisonValue::get(Int8PtrTyPrivate);
+    Value *UndefInt32 = PoisonValue::get(Int32Ty);
 
     Constant *GS = Builder.CreateGlobalString(kOCLBuiltinName::FPGARegIntel);
 
@@ -4067,8 +4067,8 @@ void SPIRVToLLVM::transIntelFPGADecorations(SPIRVValue *BV, Value *V) {
     Type *Int8PtrTyPrivate = PointerType::get(*Context, SPIRAS_Private);
     IntegerType *Int32Ty = IntegerType::get(*Context, 32);
 
-    Value *UndefInt8Ptr = UndefValue::get(Int8PtrTyPrivate);
-    Value *UndefInt32 = UndefValue::get(Int32Ty);
+    Value *UndefInt8Ptr = PoisonValue::get(Int8PtrTyPrivate);
+    Value *UndefInt32 = PoisonValue::get(Int32Ty);
 
     if (AL && BV->getType()->getPointerElementType()->isTypeStruct()) {
       auto *ST = BV->getType()->getPointerElementType();
@@ -4205,8 +4205,8 @@ void SPIRVToLLVM::transIntelFPGADecorations(SPIRVValue *BV, Value *V) {
 
       llvm::Constant *Fields[5] = {
           C, ConstantExpr::getBitCast(GS, Int8PtrTyPrivate),
-          UndefValue::get(Int8PtrTyPrivate), UndefValue::get(Int32Ty),
-          UndefValue::get(Int8PtrTyPrivate)};
+          PoisonValue::get(Int8PtrTyPrivate), PoisonValue::get(Int32Ty),
+          PoisonValue::get(Int8PtrTyPrivate)};
 
       GlobalAnnotations.push_back(ConstantStruct::getAnon(Fields));
     }
@@ -4266,8 +4266,8 @@ void SPIRVToLLVM::transUserSemantic(SPIRV::SPIRVFunction *Fun) {
 
     llvm::Constant *Fields[5] = {
         C, ConstantExpr::getBitCast(GS, Int8PtrTyPrivate),
-        UndefValue::get(Int8PtrTyPrivate), UndefValue::get(Int32Ty),
-        UndefValue::get(Int8PtrTyPrivate)};
+        PoisonValue::get(Int8PtrTyPrivate), PoisonValue::get(Int32Ty),
+        PoisonValue::get(Int8PtrTyPrivate)};
     GlobalAnnotations.push_back(ConstantStruct::getAnon(Fields));
   }
 }
@@ -4624,7 +4624,7 @@ bool SPIRVToLLVM::transMetadata() {
       std::vector<Metadata *> MetadataVec;
       Type *VecHintTy = decodeVecTypeHint(*Context, EM->getLiterals()[0]);
       assert(VecHintTy);
-      MetadataVec.push_back(ValueAsMetadata::get(UndefValue::get(VecHintTy)));
+      MetadataVec.push_back(ValueAsMetadata::get(PoisonValue::get(VecHintTy)));
       MetadataVec.push_back(ConstantAsMetadata::get(
           ConstantInt::get(Type::getInt32Ty(*Context), 1)));
       F->setMetadata(kSPIR2MD::VecTyHint, MDNode::get(*Context, MetadataVec));

lib/SPIRV/SPIRVRegularizeLLVM.cpp

@@ -231,7 +231,7 @@ void SPIRVRegularizeLLVMBase::buildUMulWithOverflowFunc(Function *UMulFunc) {
   // umul.with.overflow intrinsic return a structure, where the first element
   // is the multiplication result, and the second is an overflow bit.
   auto *StructTy = UMulFunc->getReturnType();
-  auto *Agg = Builder.CreateInsertValue(UndefValue::get(StructTy), Mul, {0});
+  auto *Agg = Builder.CreateInsertValue(PoisonValue::get(StructTy), Mul, {0});
   auto *Res = Builder.CreateInsertValue(Agg, Overflow, {1});
   Builder.CreateRet(Res);
 }
@@ -487,7 +487,7 @@ void regularizeWithOverflowInstrinsics(StringRef MangledName, CallInst *Call,
   Value *V2 = Builder.CreateICmpNE(V1, ConstZero);
   Type *StructI32I1Ty =
       StructType::create(Call->getContext(), {RetTy, V2->getType()});
-  Value *Undef = UndefValue::get(StructI32I1Ty);
+  Value *Undef = PoisonValue::get(StructI32I1Ty);
   Value *V3 = Builder.CreateInsertValue(Undef, V0, {0});
   Value *V4 = Builder.CreateInsertValue(V3, V2, {1});
   SmallVector<User *> Users(Call->users());
@@ -749,7 +749,7 @@ bool SPIRVRegularizeLLVMBase::regularize() {
           IRBuilder<> Builder(Cmpxchg);
           auto *Cmp = Builder.CreateICmpEQ(Res, Comparator, "cmpxchg.success");
           auto *V1 = Builder.CreateInsertValue(
-              UndefValue::get(Cmpxchg->getType()), Res, 0);
+              PoisonValue::get(Cmpxchg->getType()), Res, 0);
           auto *V2 = Builder.CreateInsertValue(V1, Cmp, 1, Cmpxchg->getName());
           Cmpxchg->replaceAllUsesWith(V2);
           ToErase.push_back(Cmpxchg);

lib/SPIRV/SPIRVToOCL.cpp

@@ -326,7 +326,7 @@ void SPIRVToOCLBase::visitCallSPIRVImageQuerySize(CallInst *CI) {
       assert(ImgQuerySizeRetEls == 2 &&
              "OpImageQuerySize[Lod] must return <2 x iN> vector type");
       GetImageSize = InsertElementInst::Create(
-          UndefValue::get(VecTy), GetImageSize, ConstantInt::get(Int32Ty, 0),
+          PoisonValue::get(VecTy), GetImageSize, ConstantInt::get(Int32Ty, 0),
           CI->getName(), CI->getIterator());
     } else {
       // get_image_dim and OpImageQuerySize returns different vector
@@ -337,7 +337,7 @@ void SPIRVToOCLBase::visitCallSPIRVImageQuerySize(CallInst *CI) {
       Constant *Mask = ConstantVector::get(MaskEls);
 
       GetImageSize = new ShuffleVectorInst(
-          GetImageSize, UndefValue::get(GetImageSize->getType()), Mask,
+          GetImageSize, PoisonValue::get(GetImageSize->getType()), Mask,
           CI->getName(), CI->getIterator());
     }
   }
@@ -779,7 +779,7 @@ void SPIRVToOCLBase::visitCallSPIRVImageSampleExplicitLodBuiltIn(CallInst *CI,
 
     if (CallSampledImg->hasOneUse()) {
       CallSampledImg->replaceAllUsesWith(
-          UndefValue::get(CallSampledImg->getType()));
+          PoisonValue::get(CallSampledImg->getType()));
       CallSampledImg->dropAllReferences();
       CallSampledImg->eraseFromParent();
     }
@@ -871,7 +871,7 @@ void SPIRVToOCLBase::visitCallSPIRVAvcINTELEvaluateBuiltIn(CallInst *CI,
 
   auto EraseVmeImageCall = [](CallInst *CI) {
     if (CI->hasOneUse()) {
-      CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
+      CI->replaceAllUsesWith(PoisonValue::get(CI->getType()));
       CI->dropAllReferences();
       CI->eraseFromParent();
     }

lib/SPIRV/SPIRVUtil.cpp

@@ -1961,7 +1961,7 @@ bool isSPIRVBuiltinVariable(GlobalVariable *GV,
 // %d = extractelement <3 x i64> %b, i32 idx
 // With:
 // %0 = call spir_func i64 @_Z13get_global_idj(i32 0) #1
-// %1 = insertelement <3 x i64> undef, i64 %0, i32 0
+// %1 = insertelement <3 x i64> poison, i64 %0, i32 0
 // %2 = call spir_func i64 @_Z13get_global_idj(i32 1) #1
 // %3 = insertelement <3 x i64> %1, i64 %2, i32 1
 // %4 = call spir_func i64 @_Z13get_global_idj(i32 2) #1
@@ -1976,7 +1976,7 @@ bool isSPIRVBuiltinVariable(GlobalVariable *GV,
 // %2 = load i64, i64 addrspace(4)* %1, align 32
 // With:
 // %0 = call spir_func i64 @_Z13get_global_idj(i32 0) #1
-// %1 = insertelement <3 x i64> undef, i64 %0, i32 0
+// %1 = insertelement <3 x i64> poison, i64 %0, i32 0
 // %2 = call spir_func i64 @_Z13get_global_idj(i32 1) #1
 // %3 = insertelement <3 x i64> %1, i64 %2, i32 1
 // %4 = call spir_func i64 @_Z13get_global_idj(i32 2) #1
@@ -2032,7 +2032,7 @@ static void replaceUsesOfBuiltinVar(Value *V, const APInt &AccumulatedOffset,
           if (!Index.isZero() || DL.getTypeSizeInBits(VecTy) !=
                                      DL.getTypeSizeInBits(Load->getType()))
             llvm_unreachable("Illegal use of a SPIR-V builtin variable");
-          Replacement = UndefValue::get(VecTy);
+          Replacement = PoisonValue::get(VecTy);
           for (unsigned I = 0; I < VecTy->getNumElements(); I++) {
             Replacement = Builder.CreateInsertElement(
                 Replacement,

test/DebugInfo/LocalAddressSpace.ll

@@ -15,7 +15,7 @@
 ; CHECK-SPIRV: Variable {{[0-9]+}} [[foo_a:[0-9]+]]
 ; CHECK-SPIRV: DebugGlobalVariable {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} {{[0-9]+}} [[foo_a]]
 
-; CHECK-LLVM: @foo.a = internal addrspace(3) global i32 undef, align 4, !dbg ![[a_dbg_expr:[0-9]+]]
+; CHECK-LLVM: @foo.a = internal addrspace(3) global i32 poison, align 4, !dbg ![[a_dbg_expr:[0-9]+]]
 ; CHECK-LLVM: ![[a_dbg_expr]] = !DIGlobalVariableExpression(var: ![[a_dbg_var:[0-9]+]],
 ; CHECK-LLVM: ![[a_dbg_var]] = distinct !DIGlobalVariable(name: "a"
 

test/DebugInfo/builtin-get-global-id.ll

@@ -28,7 +28,7 @@ entry:
   %gid = alloca i64, align 8
   %call = call spir_func i64 @_Z13get_global_idj(i32 0) #2, !dbg !10
 ; CHECK: [[I0:%[0-9]]] = call spir_func i64 @_Z13get_global_idj(i32 0) #1, !dbg [[DBG:![0-9]+]]
-; CHECK-NEXT: [[I1:%[0-9]]] = insertelement <3 x i64> undef, i64 [[I0]], i32 0, !dbg [[DBG]]
+; CHECK-NEXT: [[I1:%[0-9]]] = insertelement <3 x i64> poison, i64 [[I0]], i32 0, !dbg [[DBG]]
 ; CHECK-NEXT: [[I2:%[0-9]]] = call spir_func i64 @_Z13get_global_idj(i32 1) #1, !dbg [[DBG]]
 ; CHECK-NEXT: [[I3:%[0-9]]] = insertelement <3 x i64> [[I1]], i64 [[I2]], i32 1, !dbg [[DBG]]
 ; CHECK-NEXT: [[I4:%[0-9]]] = call spir_func i64 @_Z13get_global_idj(i32 2) #1, !dbg [[DBG]]

test/OpDecorateString_UserSemantic.spvasm

@@ -18,7 +18,7 @@
                ; the SPIR-V LLVM Translator and not rejected by spirv-val.
                OpDecorateString %temp UserSemantic "foo"
 ; CHECK: [[STR:@[0-9_.]+]] = {{.*}}foo
-; CHECK: call void @llvm.var.annotation.p0.p0(ptr %{{.*}}, ptr [[STR]], ptr undef, i32 undef, ptr undef)
+; CHECK: call void @llvm.var.annotation.p0.p0(ptr %{{.*}}, ptr [[STR]], ptr poison, i32 poison, ptr poison)
        %uint = OpTypeInt 32 0
        %void = OpTypeVoid
  %kernel_sig = OpTypeFunction %void %uint

test/OpMemberDecorateString_UserSemantic.spvasm

@@ -18,7 +18,7 @@
 ; CHECK: [[STR:@[0-9_.]+]] = {{.*}}foo
 ; Note: this is checking for an annotation on an instantiation of the structure,
 ; which is different than an annotation on the structure type.
-; CHECK: call ptr @llvm.ptr.annotation.p0.p0(ptr %{{.*}}, ptr [[STR]], ptr undef, i32 undef, ptr undef)
+; CHECK: call ptr @llvm.ptr.annotation.p0.p0(ptr %{{.*}}, ptr [[STR]], ptr poison, i32 poison, ptr poison)
        %uint = OpTypeInt 32 0
      %uint_0 = OpConstant %uint 0
        %void = OpTypeVoid