[mlir] SCCP add missing pessimistic setting

[jpienaar]

Summary

When this was updated in D127139 the update in-place case was no longer
marked as pessimistic. Add back in.

[rriddle]

Is there no test we can add here?

[jpienaar]

In D130453#3674840, @rriddle wrote:

Is there no test we can add here?

Yes we should be able to. My current test case is a larger computation that is producing incorrect results due to folding, and not quite getting to small test case. I'll try some more tomorrow.

[jpienaar]

Add test suggested by Mogball

[Mogball]

Thanks!

mlir/test/Transforms/sccp.mlir

220

nit: can you name this "inplace_fold" or something similar?

mlir/lib/Analysis/DataFlow/ConstantPropagationAnalysis.cpp

void SparseConstantPropagation::visitOperation(
   }
 
   // If the folding was in-place, mark the results as overdefined and reset
   // the operation. We don't allow in-place folds as the desire here is for
   // simulated execution, and not general folding.
   if (foldResults.empty()) {
     op->setOperands(originalOperands);
     op->setAttrs(originalAttrs);
+    markAllPessimisticFixpoint(results);
     return;
   }
 
   // Merge the fold results into the lattice for this operation.
   assert(foldResults.size() == op->getNumResults() && "invalid result size");
   for (const auto it : llvm::zip(results, foldResults)) {
     Lattice<ConstantValue> *lattice = std::get<0>(it);
 

mlir/test/Transforms/sccp.mlir

^bb1:
   cf.br ^bb2(%1, %1 : i32, i32)
 
 ^bb2(%arg1 : i32, %arg2 : i32):
   // CHECK: ^bb2(%[[ARG:.*]]: i32, %{{.*}}: i32):
   // CHECK: return %[[ARG]], %[[ONE]] : i32, i32
 
   return %arg1, %arg2 : i32, i32
 }
+
+// CHECK-LABEL: inplace_fold
+func.func @inplace_fold(%arg: i1) -> (i32) {
+  %0 = "test.op_in_place_fold_success"() : () -> i1
+  %1 = arith.constant 5 : i32
+  cf.cond_br %0, ^a, ^b
+
+^a:
+  // CHECK-NOT: addi
+  %3 = arith.addi %1, %1 : i32
+  return %3 : i32
+
+^b:
+  return %1 : i32
+}
+

mlir/test/lib/Dialect/Test/TestOps.td

 }
 
 def TestOpInPlaceFold : TEST_Op<"op_in_place_fold"> {
   let arguments = (ins I32:$op, I32Attr:$attr);
   let results = (outs I32);
   let hasFolder = 1;
 }
 
+// Test op that simply returns success.
+def TestOpInPlaceFoldSuccess : TEST_Op<"op_in_place_fold_success"> {
+  let results = (outs Variadic<I1>);
+  let hasFolder = 1;
+  let extraClassDefinition = [{
+    ::mlir::LogicalResult $cppClass::fold(ArrayRef<Attribute> operands,
+        SmallVectorImpl<OpFoldResult> &results) {
+      return success();
+    }
+  }];
+}
+
 // An op that always fold itself.
 def TestPassthroughFold : TEST_Op<"passthrough_fold"> {
   let arguments = (ins AnyType:$op);
   let results = (outs AnyType);
   let hasFolder = 1;
 }
 
 def TestDialectCanonicalizerOp : TEST_Op<"dialect_canonicalizable"> {