[llvm] a9b06a2 - [LCSSA] Use IRBuilder for PHI creation.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2020-08-01T18:44:15+01:00
New Revision: a9b06a2c14f9a38ba16165f0343faaa9ae713fec

URL: https://github.com/llvm/llvm-project/commit/a9b06a2c14f9a38ba16165f0343faaa9ae713fec
DIFF: https://github.com/llvm/llvm-project/commit/a9b06a2c14f9a38ba16165f0343faaa9ae713fec.diff

LOG: [LCSSA] Use IRBuilder for PHI creation.

Use IRBuilder instead PHINode::Create. This should not impact the
generated code, but IRBuilder provides a way to register callbacks for
inserted instructions, which is convenient for some users.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D85037

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/Utils/LoopUtils.h
    llvm/lib/Transforms/Utils/LCSSA.cpp
    llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index 60446bca5317..c6a8b27811ed 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -76,7 +76,7 @@ bool formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
 /// Returns true if any modifications are made.
 bool formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
                               const DominatorTree &DT, const LoopInfo &LI,
-                              ScalarEvolution *SE);
+                              ScalarEvolution *SE, IRBuilderBase &Builder);
 
 /// Put loop into LCSSA form.
 ///

diff  --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index b1a1c564d217..9c606251ae0f 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -40,6 +40,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/PredIteratorCache.h"
@@ -77,12 +78,15 @@ static bool isExitBlock(BasicBlock *BB,
 /// rewrite the uses.
 bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
                                     const DominatorTree &DT, const LoopInfo &LI,
-                                    ScalarEvolution *SE) {
+                                    ScalarEvolution *SE,
+                                    IRBuilderBase &Builder) {
   SmallVector<Use *, 16> UsesToRewrite;
   SmallSetVector<PHINode *, 16> PHIsToRemove;
   PredIteratorCache PredCache;
   bool Changed = false;
 
+  IRBuilderBase::InsertPointGuard InsertPtGuard(Builder);
+
   // Cache the Loop ExitBlocks across this loop.  We expect to get a lot of
   // instructions within the same loops, computing the exit blocks is
   // expensive, and we're not mutating the loop structure.
@@ -151,9 +155,9 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
       // If we already inserted something for this BB, don't reprocess it.
       if (SSAUpdate.HasValueForBlock(ExitBB))
         continue;
-
-      PHINode *PN = PHINode::Create(I->getType(), PredCache.size(ExitBB),
-                                    I->getName() + ".lcssa", &ExitBB->front());
+      Builder.SetInsertPoint(&ExitBB->front());
+      PHINode *PN = Builder.CreatePHI(I->getType(), PredCache.size(ExitBB),
+                                      I->getName() + ".lcssa");
       // Get the debug location from the original instruction.
       PN->setDebugLoc(I->getDebugLoc());
       // Add inputs from inside the loop for this PHI.
@@ -369,7 +373,9 @@ bool llvm::formLCSSA(Loop &L, const DominatorTree &DT, const LoopInfo *LI,
       Worklist.push_back(&I);
     }
   }
-  Changed = formLCSSAForInstructions(Worklist, DT, *LI, SE);
+
+  IRBuilder<> Builder(L.getHeader()->getContext());
+  Changed = formLCSSAForInstructions(Worklist, DT, *LI, SE, Builder);
 
   // If we modified the code, remove any caches about the loop from SCEV to
   // avoid dangling entries.

diff  --git a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
index 555da5df65e1..a8302b7ccfc1 100644
--- a/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
@@ -1951,11 +1951,8 @@ void SCEVExpander::rememberInstruction(Value *I) {
     // a defining loop. Fix LCSSA from for each operand of the new instruction,
     // if required.
     for (unsigned OpIdx = 0, OpEnd = Inst->getNumOperands(); OpIdx != OpEnd;
-         OpIdx++) {
-      auto *V = fixupLCSSAFormFor(Inst, OpIdx);
-      if (V != I)
-        DoInsert(V);
-    }
+         OpIdx++)
+      fixupLCSSAFormFor(Inst, OpIdx);
   }
 }
 
@@ -2540,7 +2537,7 @@ Value *SCEVExpander::fixupLCSSAFormFor(Instruction *User, unsigned OpIdx) {
     return OpV;
 
   ToUpdate.push_back(OpI);
-  formLCSSAForInstructions(ToUpdate, SE.DT, SE.LI, &SE);
+  formLCSSAForInstructions(ToUpdate, SE.DT, SE.LI, &SE, Builder);
   return User->getOperand(OpIdx);
 }