handle OpBitcast between pointers and non-pointers (#2948)

Adds support for SPIR-V OpBitcast instructions where the source is a pointer and the destination is not a pointer, and where the source is not a pointer and the destination is a pointer. This needs to be handled as a special case because the LLVM bitcast instruction does not support this.

Handles bitcasts between pointers and scalar integers, which is supported by all SPIR-V versions, and pointers and vectors of integers, which is supported by SPIR-V 1.5 (though only for vectors of 32-bit integers).

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@aafca810e5cd645

Author: bashbaug

llvm-spirv/lib/SPIRV/SPIRVReader.cpp

@@ -1087,6 +1087,41 @@ Value *SPIRVToLLVM::transConvertInst(SPIRVValue *BV, Function *F,
   case OpFConvert:
     CO = IsExt ? Instruction::FPExt : Instruction::FPTrunc;
     break;
+  case OpBitcast:
+    // OpBitcast need to be handled as a special-case when the source is a
+    // pointer and the destination is not a pointer, and where the source is not
+    // a pointer and the destination is a pointer. This is supported by the
+    // SPIR-V bitcast, but not by the LLVM bitcast.
+    CO = Instruction::BitCast;
+    if (Src->getType()->isPointerTy() && !Dst->isPointerTy()) {
+      if (auto *DstVecTy = dyn_cast<FixedVectorType>(Dst)) {
+        unsigned TotalBitWidth =
+            DstVecTy->getElementType()->getIntegerBitWidth() *
+            DstVecTy->getNumElements();
+        auto *IntTy = Type::getIntNTy(BB->getContext(), TotalBitWidth);
+        if (BB) {
+          Src = CastInst::CreatePointerCast(Src, IntTy, "", BB);
+        } else {
+          Src = ConstantExpr::getPointerCast(dyn_cast<Constant>(Src), IntTy);
+        }
+      } else {
+        CO = Instruction::PtrToInt;
+      }
+    } else if (!Src->getType()->isPointerTy() && Dst->isPointerTy()) {
+      if (auto *SrcVecTy = dyn_cast<FixedVectorType>(Src->getType())) {
+        unsigned TotalBitWidth =
+            SrcVecTy->getElementType()->getIntegerBitWidth() *
+            SrcVecTy->getNumElements();
+        auto *IntTy = Type::getIntNTy(BB->getContext(), TotalBitWidth);
+        if (BB) {
+          Src = CastInst::Create(Instruction::BitCast, Src, IntTy, "", BB);
+        } else {
+          Src = ConstantExpr::getBitCast(dyn_cast<Constant>(Src), IntTy);
+        }
+      }
+      CO = Instruction::IntToPtr;
+    }
+    break;
   default:
     CO = static_cast<CastInst::CastOps>(OpCodeMap::rmap(BC->getOpCode()));
   }

llvm-spirv/test/OpBitcast_ptr_scalar.spvasm

@@ -0,0 +1,31 @@
+; Check support of OpBitcast with pointer operands
+; Converts to scalar integers, which is supported by all SPIR-V versions
+
+; REQUIRES: spirv-as
+; RUN: spirv-as --target-env spv1.0 -o %t.spv %s
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis %t.rev.bc
+; RUN: FileCheck < %t.rev.ll %s --check-prefix=CHECK-LLVM
+               OpCapability Addresses
+               OpCapability Kernel
+               OpCapability Int64
+               OpMemoryModel Physical64 OpenCL
+               OpEntryPoint Kernel %kernel "test"
+       %uint = OpTypeInt 32 0
+      %ulong = OpTypeInt 64 0
+       %void = OpTypeVoid
+   %pptr_int = OpTypePointer Function %uint
+ %kernel_sig = OpTypeFunction %void
+     %kernel = OpFunction %void None %kernel_sig
+      %entry = OpLabel
+     %srcptr = OpVariable %pptr_int Function
+     %dstint = OpBitcast %ulong %srcptr
+     %dstptr = OpBitcast %pptr_int %dstint
+               OpReturn
+               OpFunctionEnd
+
+
+; CHECK-LLVM: [[SRCPTR:%[a-z0-9.]+]] = alloca i32, align 4
+; CHECK-LLVM: [[DSTINT:%[a-z0-9.]+]] = ptrtoint ptr [[SRCPTR]] to i64
+; CHECK-LLVM: [[DSTPTR:%[a-z0-9.]+]] = inttoptr i64 [[DSTINT]] to ptr

llvm-spirv/test/OpBitcast_ptr_vector.spvasm

@@ -0,0 +1,33 @@
+; Check support of OpBitcast with pointer operands
+; Converts to vectors of integers, which is supported by SPIR-V 1.5
+
+; REQUIRES: spirv-as
+; RUN: spirv-as --target-env spv1.5 -o %t.spv %s
+; RUN: spirv-val %t.spv
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis %t.rev.bc
+; RUN: FileCheck < %t.rev.ll %s --check-prefix=CHECK-LLVM
+               OpCapability Addresses
+               OpCapability Kernel
+               OpCapability Int64
+               OpMemoryModel Physical64 OpenCL
+               OpEntryPoint Kernel %kernel "test"
+       %uint = OpTypeInt 32 0
+      %uint2 = OpTypeVector %uint 2
+       %void = OpTypeVoid
+   %pptr_int = OpTypePointer Function %uint
+ %kernel_sig = OpTypeFunction %void
+     %kernel = OpFunction %void None %kernel_sig
+      %entry = OpLabel
+     %srcptr = OpVariable %pptr_int Function
+    %dstint2 = OpBitcast %uint2 %srcptr
+     %dstptr = OpBitcast %pptr_int %dstint2
+               OpReturn
+               OpFunctionEnd
+
+
+; CHECK-LLVM: [[SRCPTR:%[a-z0-9.]+]] = alloca i32, align 4
+; CHECK-LLVM: [[TMPLONG0:%[a-z0-9.]+]] = ptrtoint ptr [[SRCPTR]] to i64
+; CHECK-LLVM: [[DSTINT2:%[a-z0-9.]+]] = bitcast i64 [[TMPLONG0]] to <2 x i32>
+; CHECK-LLVM: [[TMPLONG1:%[a-z0-9.]+]] = bitcast <2 x i32> [[DSTINT2]] to i64
+; CHECK-LLVM: [[DSTPTR:%[a-z0-9.]+]] = inttoptr i64 [[TMPLONG1]] to ptr