[mlir] Add check for value that might be null.

[jacquesguan]

Summary

Because we are generating uninitialized value for no integer type and use isUninitialized() to judge if it is valid after https://reviews.llvm.org/rG93f081c896536112e1ca8133991d23cb1134793a, we should check the value before use getValue to get it.
Fixes https://github.com/llvm/llvm-project/issues/59984.

[Mogball]

I don't understand how this fixes the issue. How are you able to dereference an uninitialized optional?

[jacquesguan]

Change to check.

[jacquesguan]

In D141661#4050585, @Mogball wrote:

I don't understand how this fixes the issue. How are you able to dereference an uninitialized optional?

I change this patch to do check before use to avoid crash.

[Mogball]

Please add a test

[jacquesguan]

Add test.

[jacquesguan]

In D141661#4129435, @Mogball wrote:

Please add a test

Done.

mlir/lib/Analysis/DataFlow/IntegerRangeAnalysis.cpp

void IntegerRangeAnalysis::visitOperation(
   inferrable.inferResultRanges(argRanges, joinCallback);
 }
 
 void IntegerRangeAnalysis::visitNonControlFlowArguments(
     Operation *op, const RegionSuccessor &successor,
     ArrayRef<IntegerValueRangeLattice *> argLattices, unsigned firstIndex) {
   if (auto inferrable = dyn_cast<InferIntRangeInterface>(op)) {
     LLVM_DEBUG(llvm::dbgs() << "Inferring ranges for " << *op << "\n");
+    // If the lattice on any operand is unitialized, bail out.
+    if (llvm::any_of(op->getOperands(), [&](Value value) {
+          return getLatticeElementFor(op, value)->getValue().isUninitialized();
+        }))
+      return;
     SmallVector<ConstantIntRanges> argRanges(
         llvm::map_range(op->getOperands(), [&](Value value) {
           return getLatticeElementFor(op, value)->getValue().getValue();
         }));
 
     auto joinCallback = [&](Value v, const ConstantIntRanges &attrs) {
       auto arg = v.dyn_cast<BlockArgument>();
       if (!arg)

mlir/test/Dialect/Arith/unsigned-when-equivalent.mlir

 // Make sure not crash.
 // CHECK-LABEL: @no_integer_or_index
 func.func @no_integer_or_index() { 
   // CHECK: arith.cmpi
   %cst_0 = arith.constant dense<[0]> : vector<1xi32> 
   %cmp = arith.cmpi slt, %cst_0, %cst_0 : vector<1xi32> 
   return
 }
+
+// CHECK-LABEL: @gpu_func
+func.func @gpu_func(%arg0: memref<2x32xf32>, %arg1: memref<2x32xf32>, %arg2: memref<32xf32>, %arg3: f32, %arg4: !gpu.async.token, %arg5: index, %arg6: index) -> memref<2x32xf32> {
+  %c1 = arith.constant 1 : index  
+  %2 = gpu.launch async [%arg4] blocks(%arg7, %arg8, %arg9) in (%arg13 = %c1, %arg14 = %c1, %arg15 = %c1) threads(%arg10, %arg11, %arg12) in (%arg16 = %c1, %arg17 = %c1, %arg18 = %c1) {
+    gpu.terminator
+  } 
+  return %arg1 : memref<2x32xf32> 
+}