[LV] Clarify nature of legacy CSE (NFC)

[artagnon]

In order to avoid conflating the legacy CSE with the VPlan-based one, rename the legacy CSE and insert a FIXME to clarify the nature of the legacy CSE.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Ramkumar Ramachandra (artagnon)

Changes

In order to avoid conflating the legacy CSE with the VPlan-based one, rename the legacy CSE and insert a FIXME to clarify the nature of the legacy CSE.

---

Full diff: https://github.com/llvm/llvm-project/pull/160855.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+4-3)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index a2d61d689397b..a578b088403cb 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2438,8 +2438,9 @@ struct CSEDenseMapInfo {
 
 } // end anonymous namespace
 
-///Perform cse of induction variable instructions.
-static void cse(BasicBlock *BB) {
+/// FIXME: This legacy common-subexpression-elimination routine is scheduled for
+/// removal, in favor of the VPlan-based one.
+static void legacyCSE(BasicBlock *BB) {
   // Perform simple cse.
   SmallDenseMap<Instruction *, Instruction *, 4, CSEDenseMapInfo> CSEMap;
   for (Instruction &In : llvm::make_early_inc_range(*BB)) {
@@ -2543,7 +2544,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State) {
   BasicBlock *HeaderBB = State.CFG.VPBB2IRBB[HeaderVPBB];
 
   // Remove redundant induction instructions.
-  cse(HeaderBB);
+  legacyCSE(HeaderBB);
 }
 
 void InnerLoopVectorizer::fixNonInductionPHIs(VPTransformState &State) {

[llvmbot]

@llvm/pr-subscribers-vectorizers

Author: Ramkumar Ramachandra (artagnon)

Changes

In order to avoid conflating the legacy CSE with the VPlan-based one, rename the legacy CSE and insert a FIXME to clarify the nature of the legacy CSE.

---

Full diff: https://github.com/llvm/llvm-project/pull/160855.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+4-3)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index a2d61d689397b..a578b088403cb 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2438,8 +2438,9 @@ struct CSEDenseMapInfo {
 
 } // end anonymous namespace
 
-///Perform cse of induction variable instructions.
-static void cse(BasicBlock *BB) {
+/// FIXME: This legacy common-subexpression-elimination routine is scheduled for
+/// removal, in favor of the VPlan-based one.
+static void legacyCSE(BasicBlock *BB) {
   // Perform simple cse.
   SmallDenseMap<Instruction *, Instruction *, 4, CSEDenseMapInfo> CSEMap;
   for (Instruction &In : llvm::make_early_inc_range(*BB)) {
@@ -2543,7 +2544,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State) {
   BasicBlock *HeaderBB = State.CFG.VPBB2IRBB[HeaderVPBB];
 
   // Remove redundant induction instructions.
-  cse(HeaderBB);
+  legacyCSE(HeaderBB);
 }
 
 void InnerLoopVectorizer::fixNonInductionPHIs(VPTransformState &State) {

[fhahn]

LGTM, thanks

[llvm-ci]

LLVM Buildbot has detected a new failure on builder ppc64le-lld-multistage-test running on ppc64le-lld-multistage-test while building llvm at step 12 "build-stage2-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/168/builds/16382

Here is the relevant piece of the build log for the reference

Step 12 (build-stage2-unified-tree) failure: build (failure) (timed out)