From ab44ce3d598882e51a25eb82eb7ae6308de85ae6 Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Mon, 29 May 2017 16:25:25 +0000
Subject: Vendor import of llvm trunk r304149:
 https://llvm.org/svn/llvm-project/llvm/trunk@304149

---
 lib/CodeGen/IfConversion.cpp | 33 +++++++++------------------------
 1 file changed, 9 insertions(+), 24 deletions(-)

(limited to 'lib/CodeGen/IfConversion.cpp')

diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index 628d599a3cc7f..1c33f3b6800e1 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -39,7 +39,7 @@
 
 using namespace llvm;
 
-#define DEBUG_TYPE "ifcvt"
+#define DEBUG_TYPE "if-converter"
 
 // Hidden options for help debugging.
 static cl::opt<int> IfCvtFnStart("ifcvt-fn-start", cl::init(-1), cl::Hidden);
@@ -316,9 +316,9 @@ namespace {
 
 char &llvm::IfConverterID = IfConverter::ID;
 
-INITIALIZE_PASS_BEGIN(IfConverter, "if-converter", "If Converter", false, false)
+INITIALIZE_PASS_BEGIN(IfConverter, DEBUG_TYPE, "If Converter", false, false)
 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
-INITIALIZE_PASS_END(IfConverter, "if-converter", "If Converter", false, false)
+INITIALIZE_PASS_END(IfConverter, DEBUG_TYPE, "If Converter", false, false)
 
 bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
   if (skipFunction(*MF.getFunction()) || (PredicateFtor && !PredicateFtor(MF)))
@@ -1588,32 +1588,22 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
     BBCvt = MBPI->getEdgeProbability(BBI.BB, &CvtMBB);
   }
 
-  // To be able to insert code freely at the end of BBI we sometimes remove
-  // the branch from BBI to NextMBB temporarily. Remember if this happened.
-  bool RemovedBranchToNextMBB = false;
   if (CvtMBB.pred_size() > 1) {
     BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
     // Copy instructions in the true block, predicate them, and add them to
     // the entry block.
     CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
 
-    // Keep the CFG updated.
+    // RemoveExtraEdges won't work if the block has an unanalyzable branch, so
+    // explicitly remove CvtBBI as a successor.
     BBI.BB->removeSuccessor(&CvtMBB, true);
   } else {
     // Predicate the 'true' block after removing its branch.
     CvtBBI->NonPredSize -= TII->removeBranch(CvtMBB);
     PredicateBlock(*CvtBBI, CvtMBB.end(), Cond);
 
-    // Remove the branch from the entry of the triangle to NextBB to be able to
-    // do the merge below. Keep the CFG updated, but remember we removed the
-    // branch since we do want to execute NextMBB, either by introducing a
-    // branch to it again, or merging it into the entry block.
-    // How it's handled is decided further down.
-    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
-    BBI.BB->removeSuccessor(&NextMBB, true);
-    RemovedBranchToNextMBB = true;
-
     // Now merge the entry of the triangle with the true block.
+    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
     MergeBlocks(BBI, *CvtBBI, false);
   }
 
@@ -1651,19 +1641,12 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
     // block. By not merging them, we make it possible to iteratively
     // ifcvt the blocks.
     if (!HasEarlyExit &&
-        // We might have removed BBI from NextMBB's predecessor list above but
-        // we want it to be there, so consider that too.
-        (NextMBB.pred_size() == (RemovedBranchToNextMBB ? 0 : 1)) &&
-        !NextBBI->HasFallThrough &&
+        NextMBB.pred_size() == 1 && !NextBBI->HasFallThrough &&
         !NextMBB.hasAddressTaken()) {
-      // We will merge NextBBI into BBI, and thus remove the current
-      // fallthrough from BBI into CvtBBI.
-      BBI.BB->removeSuccessor(&CvtMBB, true);
       MergeBlocks(BBI, *NextBBI);
       FalseBBDead = true;
     } else {
       InsertUncondBranch(*BBI.BB, NextMBB, TII);
-      BBI.BB->addSuccessor(&NextMBB);
       BBI.HasFallThrough = false;
     }
     // Mixed predicated and unpredicated code. This cannot be iteratively
@@ -1671,6 +1654,8 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
     IterIfcvt = false;
   }
 
+  RemoveExtraEdges(BBI);
+
   // Update block info. BB can be iteratively if-converted.
   if (!IterIfcvt)
     BBI.IsDone = true;
-- 
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