[PATCH] D74583: Fix Block::eraseArgument when block arg is also a successor operand.

[Sean Silva via Phabricator via llvm-commits]

silvas created this revision.
silvas added a reviewer: rriddle.
Herald added subscribers: llvm-commits, Joonsoo, liufengdb, lucyrfox, mgester, arpith-jacob, nicolasvasilache, antiagainst, shauheen, burmako, jpienaar, mehdi_amini.
Herald added 1 blocking reviewer(s): rriddle.
Herald added a project: LLVM.

This could trigger an assertion due to the block argument being used by
this block's own successor operands.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74583

Files:
  mlir/lib/IR/Block.cpp


Index: mlir/lib/IR/Block.cpp
===================================================================
--- mlir/lib/IR/Block.cpp
+++ mlir/lib/IR/Block.cpp
@@ -170,20 +170,21 @@
 void Block::eraseArgument(unsigned index, bool updatePredTerms) {
   assert(index < arguments.size());
 
+  // If requested, update predecessors. We do this first since this block might
+  // be a predecessor of itself and use this block argument as a successor
+  // operand.
+  if (updatePredTerms) {
+    // Erase this argument from each of the predecessor's terminator.
+    for (auto predIt = pred_begin(), predE = pred_end(); predIt != predE;
+         ++predIt) {
+      auto *predTerminator = (*predIt)->getTerminator();
+      predTerminator->eraseSuccessorOperand(predIt.getSuccessorIndex(), index);
+    }
+  }
+
   // Delete the argument.
   arguments[index].destroy();
   arguments.erase(arguments.begin() + index);
-
-  // If we aren't updating predecessors, there is nothing left to do.
-  if (!updatePredTerms)
-    return;
-
-  // Erase this argument from each of the predecessor's terminator.
-  for (auto predIt = pred_begin(), predE = pred_end(); predIt != predE;
-       ++predIt) {
-    auto *predTerminator = (*predIt)->getTerminator();
-    predTerminator->eraseSuccessorOperand(predIt.getSuccessorIndex(), index);
-  }
 }
 
 /// Insert one value to the given position of the argument list. The existing


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D74583.244549.patch
Type: text/x-patch
Size: 1400 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200214/4a1ed5e0/attachment.bin>