Post commit fixes

This CL introduces a hotfix post refactoring of NestedMatchers:
- fix uninitialized read to skip
- avoid bumpptr allocating with 0 elements

Interestingly the latter issue only surfaced in fastbuild mode with no-san and
manifested itself by a SIGILL. All other combinations that were tried failed to
reproduce the issue (dbg, opt, fastbuild with asan)

PiperOrigin-RevId: 231787642

1 files changed, 6 insertions, 4 deletions

diff --git a/mlir/lib/Analysis/NestedMatcher.cpp b/mlir/lib/Analysis/NestedMatcher.cpp
index 43e3b332a58..46bf5ad0b97 100644
--- a/mlir/lib/Analysis/NestedMatcher.cpp
+++ b/mlir/lib/Analysis/NestedMatcher.cpp
@@ -51,10 +51,12 @@ llvm::BumpPtrAllocator *&NestedPattern::allocator() {
 NestedPattern::NestedPattern(Instruction::Kind k,
                              ArrayRef<NestedPattern> nested,
                              FilterFunctionType filter)
-    : kind(k), nestedPatterns(ArrayRef<NestedPattern>(nested)), filter(filter) {
-  auto *newNested = allocator()->Allocate<NestedPattern>(nested.size());
-  std::uninitialized_copy(nested.begin(), nested.end(), newNested);
-  nestedPatterns = ArrayRef<NestedPattern>(newNested, nested.size());
+    : kind(k), nestedPatterns(), filter(filter), skip(nullptr) {
+  if (!nested.empty()) {
+    auto *newNested = allocator()->Allocate<NestedPattern>(nested.size());
+    std::uninitialized_copy(nested.begin(), nested.end(), newNested);
+    nestedPatterns = ArrayRef<NestedPattern>(newNested, nested.size());
+  }
 }
 
 unsigned NestedPattern::getDepth() const {