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Date:      Sat, 14 Sep 2019 10:55:33 +0000 (UTC)
From:      Dimitry Andric <dim@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-projects@freebsd.org
Subject:   svn commit: r352318 - projects/clang900-import/contrib/llvm/lib/Transforms/Utils
Message-ID:  <201909141055.x8EAtXED044945@repo.freebsd.org>
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Author: dim
Date: Sat Sep 14 10:55:33 2019
New Revision: 352318
URL: https://svnweb.freebsd.org/changeset/base/352318

Log:
  Revert commit from upstream llvm trunk (by Hans Wennborg):
  
    Re-commit r357452 (take 3): "SimplifyCFG
    SinkCommonCodeFromPredecessors: Also sink function calls without used
    results (PR41259)"
  
    Third time's the charm.
  
    This was reverted in r363220 due to being suspected of an internal
    benchmark regression and a test failure, none of which turned out to
    be caused by this.
  
  As reported in https://bugs.llvm.org/show_bug.cgi?id=43269, this causes
  UNREACHABLE errors when compiling if_malo_pci.c for arm and aarch64.

Modified:
  projects/clang900-import/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: projects/clang900-import/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
==============================================================================
--- projects/clang900-import/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp	Sat Sep 14 10:52:20 2019	(r352317)
+++ projects/clang900-import/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp	Sat Sep 14 10:55:33 2019	(r352318)
@@ -1428,10 +1428,9 @@ HoistTerminator:
 static bool canSinkInstructions(
     ArrayRef<Instruction *> Insts,
     DenseMap<Instruction *, SmallVector<Value *, 4>> &PHIOperands) {
-  // Prune out obviously bad instructions to move. Each instruction must have
-  // exactly zero or one use, and we check later that use is by a single, common
-  // PHI instruction in the successor.
-  bool HasUse = !Insts.front()->user_empty();
+  // Prune out obviously bad instructions to move. Any non-store instruction
+  // must have exactly one use, and we check later that use is by a single,
+  // common PHI instruction in the successor.
   for (auto *I : Insts) {
     // These instructions may change or break semantics if moved.
     if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
@@ -1445,11 +1444,10 @@ static bool canSinkInstructions(
       if (C->isInlineAsm())
         return false;
 
-    // Each instruction must have zero or one use.
-    if (HasUse && !I->hasOneUse())
+    // Everything must have only one use too, apart from stores which
+    // have no uses.
+    if (!isa<StoreInst>(I) && !I->hasOneUse())
       return false;
-    if (!HasUse && !I->user_empty())
-      return false;
   }
 
   const Instruction *I0 = Insts.front();
@@ -1457,11 +1455,11 @@ static bool canSinkInstructions(
     if (!I->isSameOperationAs(I0))
       return false;
 
-  // All instructions in Insts are known to be the same opcode. If they have a
-  // use, check that the only user is a PHI or in the same block as the
-  // instruction, because if a user is in the same block as an instruction we're
-  // contemplating sinking, it must already be determined to be sinkable.
-  if (HasUse) {
+  // All instructions in Insts are known to be the same opcode. If they aren't
+  // stores, check the only user of each is a PHI or in the same block as the
+  // instruction, because if a user is in the same block as an instruction
+  // we're contemplating sinking, it must already be determined to be sinkable.
+  if (!isa<StoreInst>(I0)) {
     auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
     auto *Succ = I0->getParent()->getTerminator()->getSuccessor(0);
     if (!all_of(Insts, [&PNUse,&Succ](const Instruction *I) -> bool {
@@ -1539,7 +1537,7 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> 
   // it is slightly over-aggressive - it gets confused by commutative instructions
   // so double-check it here.
   Instruction *I0 = Insts.front();
-  if (!I0->user_empty()) {
+  if (!isa<StoreInst>(I0)) {
     auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
     if (!all_of(Insts, [&PNUse](const Instruction *I) -> bool {
           auto *U = cast<Instruction>(*I->user_begin());
@@ -1597,10 +1595,11 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> 
       I0->andIRFlags(I);
     }
 
-  if (!I0->user_empty()) {
+  if (!isa<StoreInst>(I0)) {
     // canSinkLastInstruction checked that all instructions were used by
     // one and only one PHI node. Find that now, RAUW it to our common
     // instruction and nuke it.
+    assert(I0->hasOneUse());
     auto *PN = cast<PHINode>(*I0->user_begin());
     PN->replaceAllUsesWith(I0);
     PN->eraseFromParent();

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