[llvm] f6b6fb8 - [VectorUtils] Improve computeMinimumValueSizes (NFC) (#137692)

[via llvm-commits]

Author: Ramkumar Ramachandra
Date: 2025-04-29T10:36:26+01:00
New Revision: f6b6fb89ec291f677132f912030b9d57c5f7230e

URL: https://github.com/llvm/llvm-project/commit/f6b6fb89ec291f677132f912030b9d57c5f7230e
DIFF: https://github.com/llvm/llvm-project/commit/f6b6fb89ec291f677132f912030b9d57c5f7230e.diff

LOG: [VectorUtils] Improve computeMinimumValueSizes (NFC) (#137692)

The Worklist used by computeMinimumValueSizes is wastefully a
Value-vector, when the top of the loop attempts to cast the popped value
to an Instruction anyway. Improve the algorithm by cutting this wasteful
work, refining the type of Worklist, Visited, and Roots from
Value-vectors to Instruction-vectors.

Added: 
    

Modified: 
    llvm/lib/Analysis/VectorUtils.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp
index 4d394ea4d99c0..682066dc5af5f 100644
--- a/llvm/lib/Analysis/VectorUtils.cpp
+++ b/llvm/lib/Analysis/VectorUtils.cpp
@@ -750,9 +750,9 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
   // to ensure no extra casts would need to be inserted, so every DAG
   // of connected values must have the same minimum bitwidth.
   EquivalenceClasses<Value *> ECs;
-  SmallVector<Value *, 16> Worklist;
-  SmallPtrSet<Value *, 4> Roots;
-  SmallPtrSet<Value *, 16> Visited;
+  SmallVector<Instruction *, 16> Worklist;
+  SmallPtrSet<Instruction *, 4> Roots;
+  SmallPtrSet<Instruction *, 16> Visited;
   DenseMap<Value *, uint64_t> DBits;
   SmallPtrSet<Instruction *, 4> InstructionSet;
   MapVector<Instruction *, uint64_t> MinBWs;
@@ -786,17 +786,12 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
 
   // Now proceed breadth-first, unioning values together.
   while (!Worklist.empty()) {
-    Value *Val = Worklist.pop_back_val();
-    Value *Leader = ECs.getOrInsertLeaderValue(Val);
+    Instruction *I = Worklist.pop_back_val();
+    Value *Leader = ECs.getOrInsertLeaderValue(I);
 
-    if (!Visited.insert(Val).second)
+    if (!Visited.insert(I).second)
       continue;
 
-    // Non-instructions terminate a chain successfully.
-    if (!isa<Instruction>(Val))
-      continue;
-    Instruction *I = cast<Instruction>(Val);
-
     // If we encounter a type that is larger than 64 bits, we can't represent
     // it so bail out.
     if (DB.getDemandedBits(I).getBitWidth() > 64)
@@ -836,9 +831,10 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
       // All bits demanded, no point continuing.
       continue;
 
-    for (Value *O : cast<User>(I)->operands()) {
+    for (Value *O : I->operands()) {
       ECs.unionSets(Leader, O);
-      Worklist.push_back(O);
+      if (auto *OI = dyn_cast<Instruction>(O))
+        Worklist.push_back(OI);
     }
   }
 
@@ -879,7 +875,7 @@ llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
       if (!MI)
         continue;
       Type *Ty = M->getType();
-      if (Roots.count(M))
+      if (Roots.count(MI))
         Ty = MI->getOperand(0)->getType();
 
       if (MinBW >= Ty->getScalarSizeInBits())