[mlir] Make remove-dead-values pass remove blocks arguments first

mlir/lib/Transforms/RemoveDeadValues.cpp

@@ -742,7 +742,25 @@ static void processBranchOp(BranchOpInterface branchOp, RunLivenessAnalysis &la,
 static void cleanUpDeadVals(RDVFinalCleanupList &list) {
   LDBG() << "Starting cleanup of dead values...";
 
-  // 1. Operations
+  // 1. Blocks
+  LDBG() << "Cleaning up " << list.blocks.size() << " block argument lists";
+  for (auto &b : list.blocks) {
+    // blocks that are accessed via multiple codepaths processed once
+    if (b.b->getNumArguments() != b.nonLiveArgs.size())
+      continue;
+    LDBG() << "Erasing " << b.nonLiveArgs.count()
+           << " non-live arguments from block: " << b.b;
+    // it iterates backwards because erase invalidates all successor indexes
+    for (int i = b.nonLiveArgs.size() - 1; i >= 0; --i) {
+      if (!b.nonLiveArgs[i])
+        continue;
+      LDBG() << "  Erasing block argument " << i << ": " << b.b->getArgument(i);
+      b.b->getArgument(i).dropAllUses();
+      b.b->eraseArgument(i);
+    }
+  }
+
+  // 2. Operations
   LDBG() << "Cleaning up " << list.operations.size() << " operations";
   for (auto &op : list.operations) {
     LDBG() << "Erasing operation: "
@@ -751,14 +769,14 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
     op->erase();
   }
 
-  // 2. Values
+  // 3. Values
   LDBG() << "Cleaning up " << list.values.size() << " values";
   for (auto &v : list.values) {
     LDBG() << "Dropping all uses of value: " << v;
     v.dropAllUses();
   }
 
-  // 3. Functions
+  // 4. Functions
   LDBG() << "Cleaning up " << list.functions.size() << " functions";
   // Record which function arguments were erased so we can shrink call-site
   // argument segments for CallOpInterface operations (e.g. ops using
@@ -780,7 +798,7 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
     (void)f.funcOp.eraseResults(f.nonLiveRets);
   }
 
-  // 4. Operands
+  // 5. Operands
   LDBG() << "Cleaning up " << list.operands.size() << " operand lists";
   for (OperationToCleanup &o : list.operands) {
     // Handle call-specific cleanup only when we have a cached callee reference.
@@ -822,7 +840,7 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
     }
   }
 
-  // 5. Results
+  // 6. Results
   LDBG() << "Cleaning up " << list.results.size() << " result lists";
   for (auto &r : list.results) {
     LDBG() << "Erasing " << r.nonLive.count()
@@ -831,24 +849,6 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
     dropUsesAndEraseResults(r.op, r.nonLive);
   }
 
-  // 6. Blocks
-  LDBG() << "Cleaning up " << list.blocks.size() << " block argument lists";
-  for (auto &b : list.blocks) {
-    // blocks that are accessed via multiple codepaths processed once
-    if (b.b->getNumArguments() != b.nonLiveArgs.size())
-      continue;
-    LDBG() << "Erasing " << b.nonLiveArgs.count()
-           << " non-live arguments from block: " << b.b;
-    // it iterates backwards because erase invalidates all successor indexes
-    for (int i = b.nonLiveArgs.size() - 1; i >= 0; --i) {
-      if (!b.nonLiveArgs[i])
-        continue;
-      LDBG() << "  Erasing block argument " << i << ": " << b.b->getArgument(i);
-      b.b->getArgument(i).dropAllUses();
-      b.b->eraseArgument(i);
-    }
-  }
-
   // 7. Successor Operands
   LDBG() << "Cleaning up " << list.successorOperands.size()
          << " successor operand lists";

mlir/test/Transforms/remove-dead-values.mlir

@@ -674,3 +674,18 @@ func.func @dead_value_loop_ivs_no_result(%lb: index, %ub: index, %step: index, %
   }
   return
 }
+
+// -----
+
+// CHECK-LABEL: func @op_block_have_dead_arg
+func.func @op_block_have_dead_arg(%arg0: index, %arg1: index, %arg2: index, %arg3: i1) {
+  scf.for %iv = %arg0 to %arg1 step %arg2 {
+    scf.execute_region {
+      cf.cond_br %arg3, ^bb1(%arg0 : index), ^bb1(%arg1 : index)
+    ^bb1(%0: index):
+        scf.yield
+    }
+  }
+// CHECK-NEXT: return
+  return
+}