From 8928b46f982c7c3418ff7444b3ab2c2ec2df4d27 Mon Sep 17 00:00:00 2001
From: Kang Zhang <shkzhang@cn.ibm.com>
Date: Fri, 2 Aug 2019 03:09:07 +0000
Subject: [PATCH] [NFC][CodeGen] Modify the type element of TailCalls to
 simplify the dupRetToEnableTailCallOpts()

Summary:
The old code can be simplified to define the element type of TailCalls as `BasicBlock` not `CallInst`. Also I use the for-range loop instead the for loop.

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D64905


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367644 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CodeGenPrepare.cpp | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index 52b4bbea012..511b7f73857 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -2024,17 +2024,18 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB, bool &ModifiedDT
   /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
   /// call.
   const Function *F = BB->getParent();
-  SmallVector<CallInst*, 4> TailCalls;
+  SmallVector<BasicBlock*, 4> TailCallBBs;
   if (PN) {
     for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
       // Look through bitcasts.
       Value *IncomingVal = PN->getIncomingValue(I)->stripPointerCasts();
       CallInst *CI = dyn_cast<CallInst>(IncomingVal);
+      BasicBlock *PredBB = PN->getIncomingBlock(I);
       // Make sure the phi value is indeed produced by the tail call.
-      if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
+      if (CI && CI->hasOneUse() && CI->getParent() == PredBB &&
           TLI->mayBeEmittedAsTailCall(CI) &&
           attributesPermitTailCall(F, CI, RetI, *TLI))
-        TailCalls.push_back(CI);
+        TailCallBBs.push_back(PredBB);
     }
   } else {
     SmallPtrSet<BasicBlock*, 4> VisitedBBs;
@@ -2052,24 +2053,20 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB, bool &ModifiedDT
       CallInst *CI = dyn_cast<CallInst>(&*RI);
       if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI) &&
           attributesPermitTailCall(F, CI, RetI, *TLI))
-        TailCalls.push_back(CI);
+        TailCallBBs.push_back(*PI);
     }
   }
 
   bool Changed = false;
-  for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
-    CallInst *CI = TailCalls[i];
-    CallSite CS(CI);
-
+  for (auto const &TailCallBB : TailCallBBs) {
     // Make sure the call instruction is followed by an unconditional branch to
     // the return block.
-    BasicBlock *CallBB = CI->getParent();
-    BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
+    BranchInst *BI = dyn_cast<BranchInst>(TailCallBB->getTerminator());
     if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
       continue;
 
-    // Duplicate the return into CallBB.
-    (void)FoldReturnIntoUncondBranch(RetI, BB, CallBB);
+    // Duplicate the return into TailCallBB.
+    (void)FoldReturnIntoUncondBranch(RetI, BB, TailCallBB);
     ModifiedDT = Changed = true;
     ++NumRetsDup;
   }
-- 
2.49.0