remove UB canonicalization

Author: matthias-springer

mlir/include/mlir/Dialect/ControlFlow/IR/ControlFlowOps.td

@@ -22,7 +22,7 @@ include "mlir/Interfaces/SideEffectInterfaces.td"
 def ControlFlow_Dialect : Dialect {
   let name = "cf";
   let cppNamespace = "::mlir::cf";
-  let dependentDialects = ["arith::ArithDialect", "ub::UBDialect"];
+  let dependentDialects = ["arith::ArithDialect"];
   let description = [{
     This dialect contains low-level, i.e. non-region based, control flow
     constructs. These constructs generally represent control flow directly

mlir/include/mlir/Dialect/UB/IR/UBOps.td

@@ -84,7 +84,6 @@ def UnreachableOp : UB_Op<"unreachable", [Terminator]> {
   }];
 
   let assemblyFormat = "attr-dict";
-  let hasCanonicalizeMethod = 1;
 }
 
 #endif // MLIR_DIALECT_UB_IR_UBOPS_TD

mlir/lib/Dialect/ControlFlow/IR/ControlFlowOps.cpp

@@ -447,6 +447,8 @@ struct CondBranchTruthPropagation : public OpRewritePattern<CondBranchOp> {
   }
 };
 
+/// If the destination block of a conditional branch contains only
+/// ub.unreachable, unconditionally branch to the other destination.
 struct DropUnreachableCondBranch : public OpRewritePattern<CondBranchOp> {
   using OpRewritePattern<CondBranchOp>::OpRewritePattern;
 

mlir/lib/Dialect/UB/IR/UBOps.cpp

@@ -12,7 +12,6 @@
 
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/DialectImplementation.h"
-#include "mlir/IR/PatternMatch.h"
 #include "llvm/ADT/TypeSwitch.h"
 
 #include "mlir/Dialect/UB/IR/UBOpsDialect.cpp.inc"
@@ -58,33 +57,8 @@ Operation *UBDialect::materializeConstant(OpBuilder &builder, Attribute value,
   return nullptr;
 }
 
-//===----------------------------------------------------------------------===//
-// PoisonOp
-//===----------------------------------------------------------------------===//
-
 OpFoldResult PoisonOp::fold(FoldAdaptor /*adaptor*/) { return getValue(); }
 
-//===----------------------------------------------------------------------===//
-// UnreachableOp
-//===----------------------------------------------------------------------===//
-
-LogicalResult UnreachableOp::canonicalize(UnreachableOp unreachableOp,
-                                          PatternRewriter &rewriter) {
-  Block *block = unreachableOp->getBlock();
-  if (llvm::hasSingleElement(*block))
-    return rewriter.notifyMatchFailure(
-        unreachableOp, "unreachable op is the only operation in the block");
-
-  // Erase all other operations in the block. They must be dead.
-  for (Operation &op : llvm::make_early_inc_range(*block)) {
-    if (&op == unreachableOp.getOperation())
-      continue;
-    op.dropAllUses();
-    rewriter.eraseOp(&op);
-  }
-  return success();
-}
-
 #include "mlir/Dialect/UB/IR/UBOpsInterfaces.cpp.inc"
 
 #define GET_ATTRDEF_CLASSES

mlir/test/Dialect/ControlFlow/canonicalize.mlir

@@ -644,7 +644,6 @@ func.func @drop_unreachable_branch_1(%c: i1) {
   "test.foo"() : () -> ()
   return
 ^bb2:
-  "test.bar"() : () -> ()
   ub.unreachable
 }
 
@@ -653,9 +652,7 @@ func.func @drop_unreachable_branch_1(%c: i1) {
 func.func @drop_unreachable_branch_2(%c: i1) {
   cf.cond_br %c, ^bb1, ^bb2
 ^bb1:
-  "test.foo"() : () -> ()
   ub.unreachable
 ^bb2:
-  "test.bar"() : () -> ()
   ub.unreachable
 }

mlir/test/Dialect/UB/canonicalize.mlir

@@ -9,13 +9,3 @@ func.func @merge_poison() -> (i32, i32) {
   %1 = ub.poison : i32
   return %0, %1 : i32, i32
 }
-
-// -----
-
-// CHECK-LABEL: func @drop_ops_before_unreachable() 
-//  CHECK-NEXT:   ub.unreachable
-func.func @drop_ops_before_unreachable() {
-  "test.foo"() : () -> ()
-  "test.bar"() : () -> ()
-  ub.unreachable
-}