https://github.com/matthias-springer created https://github.com/llvm/llvm-project/pull/179104
Erase ops that precede `ub.unreachable` if they must progress, i.e., it's guaranteed that their next operation is reached. Depends on #179039. >From d5711dd0c64bd90d866bf78a3f9beb70afda2773 Mon Sep 17 00:00:00 2001 From: Matthias Springer <[email protected]> Date: Sun, 1 Feb 2026 12:29:56 +0000 Subject: [PATCH] [mlir][UB] Erase ops that precede `ub.unreachable` --- mlir/include/mlir/Dialect/UB/IR/UBOps.td | 1 + mlir/lib/Dialect/UB/IR/UBOps.cpp | 37 ++++++++++++++++++++++++ mlir/test/Dialect/UB/canonicalize.mlir | 25 ++++++++++++++++ 3 files changed, 63 insertions(+) diff --git a/mlir/include/mlir/Dialect/UB/IR/UBOps.td b/mlir/include/mlir/Dialect/UB/IR/UBOps.td index 1bff39add691e..95c52db404912 100644 --- a/mlir/include/mlir/Dialect/UB/IR/UBOps.td +++ b/mlir/include/mlir/Dialect/UB/IR/UBOps.td @@ -84,6 +84,7 @@ def UnreachableOp : UB_Op<"unreachable", [Terminator]> { }]; let assemblyFormat = "attr-dict"; + let hasCanonicalizeMethod = 1; } #endif // MLIR_DIALECT_UB_IR_UBOPS_TD diff --git a/mlir/lib/Dialect/UB/IR/UBOps.cpp b/mlir/lib/Dialect/UB/IR/UBOps.cpp index 9c8ad2ddb2c6a..66dfceaffc6dd 100644 --- a/mlir/lib/Dialect/UB/IR/UBOps.cpp +++ b/mlir/lib/Dialect/UB/IR/UBOps.cpp @@ -59,8 +59,45 @@ 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) { + // Erase operations that precede ub.unreachable (if they must progress). + 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. + auto it = unreachableOp->getIterator(); + --it; + bool reachedBegin = false; + bool changed = false; + do { + Operation *op = &*it; + // Do not erase ops that may not progress (and ops that precede them). + if (!mustProgress(op)) + break; + reachedBegin = it == block->begin(); + if (!reachedBegin) + --it; + rewriter.eraseOp(op); + changed = true; + if (reachedBegin) + break; + } while (!reachedBegin); + return success(changed); +} + #include "mlir/Dialect/UB/IR/UBOpsInterfaces.cpp.inc" #define GET_ATTRDEF_CLASSES diff --git a/mlir/test/Dialect/UB/canonicalize.mlir b/mlir/test/Dialect/UB/canonicalize.mlir index c3f286e49b09b..bd8cc99449b7e 100644 --- a/mlir/test/Dialect/UB/canonicalize.mlir +++ b/mlir/test/Dialect/UB/canonicalize.mlir @@ -9,3 +9,28 @@ func.func @merge_poison() -> (i32, i32) { %1 = ub.poison : i32 return %0, %1 : i32, i32 } + +// ----- + +// CHECK-LABEL: func @drop_ops_before_unreachable( +// CHECK-NEXT: arith.constant +// CHECK-NEXT: arith.constant +// CHECK-NEXT: arith.constant +// CHECK-NEXT: vector.print +// CHECK-NEXT: scf.for {{.*}} { +// CHECK-NEXT: vector.print +// CHECK-NEXT: } +// CHECK-NEXT: ub.unreachable +func.func @drop_ops_before_unreachable(%arg0: i32) { + %lb = arith.constant 3 : index + %ub = arith.constant 4 : index + %step = arith.constant 0 : index + vector.print %arg0 : i32 + // Infinite loop that may not progress. Such ops (and everything before) + // is not erased. + scf.for %iv = %lb to %ub step %step { + vector.print %arg0 : i32 + } {mustProgress = false} + vector.print %arg0 : i32 + ub.unreachable +} _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
