Translate constant global variable references correctly in opaque pointer mode. (#1666)

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@81464b0

Author: jcranmer-intel

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -1049,6 +1049,32 @@ void LLVMToSPIRVBase::transFPGAFunctionMetadata(SPIRVFunction *BF,
   }
 }
 
+SPIRVValue *LLVMToSPIRVBase::transConstantUse(Constant *C) {
+  // Constant expressions expect their pointer types to be i8* in opaque pointer
+  // mode, but the value may have a different "natural" type. If that is the
+  // case, we need to adjust the type of the constant.
+  SPIRVValue *Trans = transValue(C, nullptr, true, FuncTransMode::Pointer);
+  SPIRVType *ExpectedType = transType(C->getType());
+  if (Trans->getType() == ExpectedType || Trans->getType()->isTypePipeStorage())
+    return Trans;
+
+  assert(C->getType()->isPointerTy() &&
+         "Only pointer type mismatches should be possible");
+  // In the common case of strings ([N x i8] GVs), see if we can emit a GEP
+  // instruction.
+  if (auto *GV = dyn_cast<GlobalVariable>(C)) {
+    if (GV->getValueType()->isArrayTy() &&
+        GV->getValueType()->getArrayElementType()->isIntegerTy(8)) {
+      SPIRVValue *Offset = transValue(getUInt32(M, 0), nullptr);
+      return BM->addPtrAccessChainInst(ExpectedType, Trans, {Offset, Offset},
+                                       nullptr, true);
+    }
+  }
+
+  // Otherwise, just use a bitcast.
+  return BM->addUnaryInst(OpBitcast, ExpectedType, Trans, nullptr);
+}
+
 SPIRVValue *LLVMToSPIRVBase::transConstant(Value *V) {
   if (auto CPNull = dyn_cast<ConstantPointerNull>(V))
     return BM->addNullConstant(
@@ -1085,30 +1111,28 @@ SPIRVValue *LLVMToSPIRVBase::transConstant(Value *V) {
   if (auto ConstDA = dyn_cast<ConstantDataArray>(V)) {
     std::vector<SPIRVValue *> BV;
     for (unsigned I = 0, E = ConstDA->getNumElements(); I != E; ++I)
-      BV.push_back(transValue(ConstDA->getElementAsConstant(I), nullptr, true,
-                              FuncTransMode::Pointer));
+      BV.push_back(transConstantUse(ConstDA->getElementAsConstant(I)));
     return BM->addCompositeConstant(transType(V->getType()), BV);
   }
 
   if (auto ConstA = dyn_cast<ConstantArray>(V)) {
     std::vector<SPIRVValue *> BV;
     for (auto I = ConstA->op_begin(), E = ConstA->op_end(); I != E; ++I)
-      BV.push_back(transValue(*I, nullptr, true, FuncTransMode::Pointer));
+      BV.push_back(transConstantUse(cast<Constant>(*I)));
     return BM->addCompositeConstant(transType(V->getType()), BV);
   }
 
   if (auto ConstDV = dyn_cast<ConstantDataVector>(V)) {
     std::vector<SPIRVValue *> BV;
     for (unsigned I = 0, E = ConstDV->getNumElements(); I != E; ++I)
-      BV.push_back(transValue(ConstDV->getElementAsConstant(I), nullptr, true,
-                              FuncTransMode::Pointer));
+      BV.push_back(transConstantUse(ConstDV->getElementAsConstant(I)));
     return BM->addCompositeConstant(transType(V->getType()), BV);
   }
 
   if (auto ConstV = dyn_cast<ConstantVector>(V)) {
     std::vector<SPIRVValue *> BV;
     for (auto I = ConstV->op_begin(), E = ConstV->op_end(); I != E; ++I)
-      BV.push_back(transValue(*I, nullptr, true, FuncTransMode::Pointer));
+      BV.push_back(transConstantUse(cast<Constant>(*I)));
     return BM->addCompositeConstant(transType(V->getType()), BV);
   }
 
@@ -1148,7 +1172,7 @@ SPIRVValue *LLVMToSPIRVBase::transConstant(Value *V) {
     }
     std::vector<SPIRVValue *> BV;
     for (auto I = ConstV->op_begin(), E = ConstV->op_end(); I != E; ++I)
-      BV.push_back(transValue(*I, nullptr, true, FuncTransMode::Pointer));
+      BV.push_back(transConstantUse(cast<Constant>(*I)));
     return BM->addCompositeConstant(transType(V->getType()), BV);
   }
 

llvm-spirv/lib/SPIRV/SPIRVWriter.h

@@ -130,6 +130,9 @@ class LLVMToSPIRVBase {
   bool transExecutionMode();
   void transFPContract();
   SPIRVValue *transConstant(Value *V);
+  /// Translate a reference to a constant in a constant expression. This may
+  /// involve inserting extra bitcasts to correct type issues.
+  SPIRVValue *transConstantUse(Constant *V);
   SPIRVValue *transValue(Value *V, SPIRVBasicBlock *BB,
                          bool CreateForward = true,
                          FuncTransMode FuncTrans = FuncTransMode::Decl);

llvm-spirv/test/transcoding/constant-vars.ll

@@ -0,0 +1,53 @@
+; Check that we can handle constant expressions correctly.
+; RUN: llvm-as %s -o %t.bc
+; RUN: llvm-spirv %t.bc -spirv-text -o - | FileCheck %s --check-prefix=CHECK-SPIRV
+; RUN: llvm-spirv %t.bc -o %t.spv
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r %t.spv -emit-opaque-pointers -o %t.rev.bc
+; RUN: llvm-dis %t.rev.bc -o - | FileCheck %s --check-prefix=CHECK-LLVM
+
+target datalayout = "e-p:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024"
+target triple = "spir-unknown-unknown"
+
+; CHECK-SPIRV-DAG: 4 TypeInt [[U8:[0-9]+]] 8 0
+; CHECK-SPIRV-DAG: 4 TypeInt [[U32:[0-9]+]] 32 0
+; CHECK-SPIRV-DAG: 4 TypeInt [[U64:[0-9]+]] 64 0
+; CHECK-SPIRV-DAG: 4 Constant [[U32]] [[I320:[0-9]+]] 0
+; CHECK-SPIRV-DAG: 4 Constant [[U32]] [[I323:[0-9]+]] 3
+; CHECK-SPIRV: 4 TypePointer [[AS2:[0-9]+]] 0 [[U8]]
+; CHECK-SPIRV: 4 TypePointer [[AS1:[0-9]+]] 5 [[U8]]
+; CHECK-SPIRV-DAG: 4 TypeStruct [[STRUCTTY:[0-9]+]]
+; CHECK-SPIRV-DAG: 4 TypeArray [[ARRAYTY:[0-9]+]] [[AS1]] [[I323]]
+
+@astr = internal addrspace(2) constant [7 x i8] c"string\00", align 4
+; CHECK-SPIRV: 5 Variable {{[0-9]+}} [[ASTR:[0-9]+]] 0
+
+@i64arr = addrspace(1) constant [3 x i64] [i64 0, i64 1, i64 2]
+; CHECK-SPIRV: 5 Variable {{[0-9]+}} [[I64ARR:[0-9]+]] 5
+
+@struct = addrspace(1) global {ptr addrspace(2), ptr addrspace(1)} { ptr addrspace(2) @astr, ptr addrspace(1) @i64arr }
+
+; CHECK-SPIRV: 7 SpecConstantOp [[AS2]] [[ASTRC:[0-9]+]] 70 [[ASTR]] [[I320]] [[I320]]
+; CHECK-SPIRV: 5 SpecConstantOp [[AS1]] [[I64ARRC:[0-9]+]] 124 [[I64ARR]]
+; CHECK-SPIRV: 5 ConstantComposite [[STRUCTTY]] [[STRUCT_INIT:[0-9]+]] [[ASTRC]] [[I64ARRC]]
+; CHECK-SPIRV: 5 Variable {{[0-9]+}} [[STRUCT:[0-9]+]] 5 [[STRUCT_INIT]]
+
+@array = addrspace(1) global [3 x ptr addrspace(1)] [ptr addrspace(1) @i64arr, ptr addrspace(1) @struct, ptr addrspace(1) getelementptr ([3 x i64], ptr addrspace(1) @i64arr, i64 0, i64 1) ]
+
+; CHECK-SPIRV: 5 SpecConstantOp [[AS1]] [[I64ARRC2:[0-9]+]] 124 [[I64ARR]]
+; CHECK-SPIRV: 5 SpecConstantOp [[AS1]] [[STRUCTC:[0-9]+]] 124 [[STRUCT]]
+; CHECK-SPIRV: 7 SpecConstantOp {{[0-9]+}} [[GEP:[0-9]+]] 70 [[I64ARR]]
+; CHECK-SPIRV: 5 SpecConstantOp [[AS1]] [[I64ARRC3:[0-9]+]] 124 [[GEP]]
+; CHECK-SPIRV: 6 ConstantComposite [[ARRAYTY]] [[ARRAY_INIT:[0-9]+]] [[I64ARRC2]] [[STRUCTC]] [[I64ARRC3]]
+; CHECK-SPIRV: 5 Variable {{[0-9]+}} [[ARRAY:[0-9]+]] 5 [[ARRAY_INIT]]
+
+; CHECK-LLVM: %structtype = type { ptr addrspace(2), ptr addrspace(1) }
+; CHECK-LLVM: @astr = internal unnamed_addr addrspace(2) constant [7 x i8] c"string\00", align 4
+; CHECK-LLVM: @i64arr = addrspace(1) constant [3 x i64] [i64 0, i64 1, i64 2]
+; CHECK-LLVM: @struct = addrspace(1) global %structtype { ptr addrspace(2) @astr, ptr addrspace(1) @i64arr }
+; CHECK-LLVM: @array = addrspace(1) global [3 x ptr addrspace(1)] [ptr addrspace(1) @i64arr, ptr addrspace(1) @struct, ptr addrspace(1) getelementptr inbounds ([3 x i64], ptr addrspace(1) @i64arr, i64 0, i64 1)]
+
+define spir_kernel void @foo() {
+  %val = load i32, ptr addrspace(2) @astr, align 4
+  ret void
+}