[mlir] Fix bug in block merging when the types of the operands differ

[rriddle]

Summary

The merging algorithm was previously not checking for type equivalence.

Fixes PR47314

[mehdi_amini]

LGTM

mlir/test/Transforms/canonicalize-block-merge.mlir

206

You're not checking anything here though, just relying on the verifier?

[rriddle]

Address comments

mlir/lib/Transforms/Utils/RegionUtils.cpp

for (int opI = 0; lhsIt != lhsE && rhsIt != rhsE; ++lhsIt, ++rhsIt, ++opI) {
     // Compare the operands of the two operations. If the operand is within
     // the block, it must refer to the same operation.
     auto lhsOperands = lhsIt->getOperands(), rhsOperands = rhsIt->getOperands();
     for (int operand : llvm::seq<int>(0, lhsIt->getNumOperands())) {
       Value lhsOperand = lhsOperands[operand];
       Value rhsOperand = rhsOperands[operand];
       if (lhsOperand == rhsOperand)
         continue;
+      // Check that the types of the operands match.
+      if (lhsOperand.getType() != rhsOperand.getType())
+        return failure();
 
       // Check that these uses are both external, or both internal.
       bool lhsIsInBlock = lhsOperand.getParentBlock() == leaderBlock;
       bool rhsIsInBlock = rhsOperand.getParentBlock() == mergeBlock;
       if (lhsIsInBlock != rhsIsInBlock)
         return failure();
       // Let the operands differ if they are defined in a different block. These
       // will become new arguments if the blocks get merged.

mlir/test/Transforms/canonicalize-block-merge.mlir

^bb2:
   cond_br %cond, ^bb1, ^bb3
 
 ^bb3:
   // CHECK: ^bb2:
   // CHECK-NEXT: return
 
   return
 }
+
+// Check that blocks are not merged if the types of the operands differ.
+
+func @mismatch_operand_types(%arg0 : i1, %arg1 : memref<i32>, %arg2 : memref<i1>) {
+  %c0_i32 = constant 0 : i32
+  %true = constant true
+  br ^bb1
+^bb1:
+  cond_br %arg0, ^bb2, ^bb3
+^bb2:
+  store %c0_i32, %arg1[] : memref<i32>
+  br ^bb1
+^bb3:
+  store %true, %arg2[] : memref<i1>
+  br ^bb1
+}