[llvm-bugs] [Bug 31948] New: NVPTXInferAddressSpaces crashes when rewriting a bitcast instruction.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=31948

            Bug ID: 31948
           Summary: NVPTXInferAddressSpaces crashes when rewriting a
                    bitcast instruction.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: PTX
          Assignee: unassignedbugs at nondot.org
          Reporter: acjacob at us.ibm.com
                CC: llvm-bugs at lists.llvm.org

I came across the issue when compiling an OpenMP program for the NVPTX target. 
I've written a simple testcase in CUDA that also exposes the crash.

---
typedef struct {
  float a;
  float *b;
} bar;

__device__ __shared__ bar var1;

__global__ void axpy(float a, float* x, float* y) {
    *(var1.b) += 1.0;
    int *p = (int *) &(var1.b);
    *p = 32;
}
---

Extract of traceback:

---
clang-5.0: llvm/lib/IR/Constants.cpp:1698: static llvm::Constant
*llvm::ConstantExpr::getBitCast(llvm::Constant *, llvm::Type *, bool):
Assertion `CastInst::castIsValid(Instruction::BitCast, C, DstTy) && "Invalid
constantexpr bitcast!"' failed.
...
#9 llvm::ConstantExpr::getBitCast(llvm::Constant*, llvm::Type*, bool)
llvm/lib/IR/Constants.cpp:1697:3
#10 cloneConstantExprWithNewAddressSpace(llvm::ConstantExpr*, unsigned int,
llvm::ValueMap<llvm::Value const*, llvm::WeakVH,
llvm::ValueMapConfig<llvm::Value const*, llvm::sys::SmartMutex<false> > >
const&) llvm/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp:347:12
#11 cloneValueWithNewAddressSpace(llvm::Value*, unsigned int,
llvm::ValueMap<llvm::Value const*, llvm::WeakVH,
llvm::ValueMapConfig<llvm::Value const*, llvm::sys::SmartMutex<false> > >
const&, llvm::SmallVectorImpl<llvm::Use const*>*)
llvm/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp:416:10
#12 (anonymous
namespace)::NVPTXInferAddressSpaces::rewriteWithNewAddressSpaces(std::vector<llvm::Value*,
std::allocator<llvm::Value*> > const&, llvm::DenseMap<llvm::Value const*,
unsigned int, llvm::DenseMapInfo<llvm::Value const*>,
llvm::detail::DenseMapPair<llvm::Value const*, unsigned int> > const&,
llvm::Function*) llvm/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp:536:34
#13 (anonymous
namespace)::NVPTXInferAddressSpaces::runOnFunction(llvm::Function&)
llvm/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp:450:10
#14 0x0000000011861dcc llvm::FPPassManager::runOnFunction(llvm::Function&)
llvm/lib/IR/LegacyPassManager.cpp:1513:27
---

A quick attempt to understand the code in this file and produce a patch
resulted in the following, but someone who understands the code better should
be able to determine the right fix.

Patch:

---
diff --git a/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp
b/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp
index 60c6d3d..a8451b0 100644
--- a/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp
+++ b/lib/Target/NVPTX/NVPTXInferAddressSpaces.cpp
@@ -343,6 +343,8 @@ static Value *cloneConstantExprWithNewAddressSpace(
     assert(CE->getOperand(0)->getType()->getPointerAddressSpace() ==
            NewAddrSpace);
     return ConstantExpr::getBitCast(CE->getOperand(0), TargetType);
+  } else if (CE->getOpcode() == Instruction::BitCast) {
+    return ConstantExpr::getAddrSpaceCast(CE->getOperand(0), TargetType);
   }

   // Computes the operands of the new constant expression.
---


Thanks,
Arpith

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