[LV] Initialize IR block pointers in ILV. (NFC)

[gchaltas]

Setting unitialized pointers to nullptr in InnerLoopVectorizer() constructor. These were noticed during a review of the code. Seems like a good idea to clean them up.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: George Chaltas (gchaltas)

Changes

Setting unitialized pointers to nullptr in InnerLoopVectorizer() constructor. These were noticed during a review of the code. Seems like a good idea to clean them up.

---

Full diff: https://github.com/llvm/llvm-project/pull/139807.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+3-3)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index d04fea5d9b0ac..742ef585cb1f7 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -603,13 +603,13 @@ class InnerLoopVectorizer {
   // --- Vectorization state ---
 
   /// The vector-loop preheader.
-  BasicBlock *LoopVectorPreHeader;
+  BasicBlock *LoopVectorPreHeader = nullptr;
 
   /// The scalar-loop preheader.
-  BasicBlock *LoopScalarPreHeader;
+  BasicBlock *LoopScalarPreHeader = nullptr;
 
   /// Middle Block between the vector and the scalar.
-  BasicBlock *LoopMiddleBlock;
+  BasicBlock *LoopMiddleBlock = nullptr;
 
   /// A list of all bypass blocks. The first block is the entry of the loop.
   SmallVector<BasicBlock *, 4> LoopBypassBlocks;

[llvmbot]

@llvm/pr-subscribers-vectorizers

Author: George Chaltas (gchaltas)

Changes

Setting unitialized pointers to nullptr in InnerLoopVectorizer() constructor. These were noticed during a review of the code. Seems like a good idea to clean them up.

---

Full diff: https://github.com/llvm/llvm-project/pull/139807.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+3-3)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index d04fea5d9b0ac..742ef585cb1f7 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -603,13 +603,13 @@ class InnerLoopVectorizer {
   // --- Vectorization state ---
 
   /// The vector-loop preheader.
-  BasicBlock *LoopVectorPreHeader;
+  BasicBlock *LoopVectorPreHeader = nullptr;
 
   /// The scalar-loop preheader.
-  BasicBlock *LoopScalarPreHeader;
+  BasicBlock *LoopScalarPreHeader = nullptr;
 
   /// Middle Block between the vector and the scalar.
-  BasicBlock *LoopMiddleBlock;
+  BasicBlock *LoopMiddleBlock = nullptr;
 
   /// A list of all bypass blocks. The first block is the entry of the loop.
   SmallVector<BasicBlock *, 4> LoopBypassBlocks;

[gchaltas]

@fhahn would you please review this and merge if you find it appropriate?

[david-arm]

LGTM!

[david-arm]

This looks like a nice fix! An alternative might be to disable the default constructor by adding

  InnerLoopVectorizer() = delete;

and then forcing the existing InnerLoopVectorizer constructor to explicitly set LoopVectorPreHeader, etc. to nullptr, as well as others such as AddedSafetyChecks? That way all the sensible defaults are being set in the same place. Any thoughts @fhahn?

[fhahn]

Yep, the default constructor should not be used.

[david-arm]

Yeah, I was just wondering if it was worth enforcing this by explicitly removing the default constructor. At the moment it feels more like an unwritten rule, although in practice it's probably not the sort of class that's going to be used frequently elsewhere.

[fhahn]

For most it is probably not worth the trouble, as it isn't expose outside LoopVectorize.cpp, and things are going to get removed gradually.

[fhahn]

LGTM, thanks.

@gchaltas do you need help merging the PR?

Would be good to adjust the title to be a bit more descriptive, maybe something like [LV] Initialize IR block pointers in ILV. (NFC)

[fhahn]

Yep, the default constructor should not be used.

[gchaltas]

@fhahn Yes please. I don't have privileges to merge. I adjusted the title per your suggestion - thank you!