From fa0e6facc793d0a67e89f873e18cd35a9d7c02e0 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 10 Mar 2011 19:51:54 +0000
Subject: [PATCH] Fix reassociate to postpone certain instruction deletions
 until after it has finished all of its reassociations, because its habit of
 unlinking operands and holding them in a datastructure while working means
 that it's not easy to determine when an instruction is really dead until
 after all its regular work is done. rdar://9096268.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127424 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/Reassociate.cpp | 14 +++++++++++---
 test/Transforms/Reassociate/crash.ll  | 25 +++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index e093b52571a..6a0fb3f7789 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -22,6 +22,7 @@
 
 #define DEBUG_TYPE "reassociate"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Function.h"
@@ -74,6 +75,7 @@ namespace {
   class Reassociate : public FunctionPass {
     DenseMap<BasicBlock*, unsigned> RankMap;
     DenseMap<AssertingVH<>, unsigned> ValueRankMap;
+    SmallVector<WeakVH, 8> DeadInsts;
     bool MadeChange;
   public:
     static char ID; // Pass identification, replacement for typeid
@@ -113,13 +115,13 @@ FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
 
 void Reassociate::RemoveDeadBinaryOp(Value *V) {
   Instruction *Op = dyn_cast<Instruction>(V);
-  if (!Op || !isa<BinaryOperator>(Op) || !Op->use_empty())
+  if (!Op || !isa<BinaryOperator>(Op))
     return;
   
   Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
   
   ValueRankMap.erase(Op);
-  Op->eraseFromParent();
+  DeadInsts.push_back(Op);
   RemoveDeadBinaryOp(LHS);
   RemoveDeadBinaryOp(RHS);
 }
@@ -603,7 +605,7 @@ Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
   // remaining operand.
   if (Factors.size() == 1) {
     ValueRankMap.erase(BO);
-    BO->eraseFromParent();
+    DeadInsts.push_back(BO);
     V = Factors[0].Op;
   } else {
     RewriteExprTree(BO, Factors);
@@ -1093,6 +1095,12 @@ bool Reassociate::runOnFunction(Function &F) {
   for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
     ReassociateBB(FI);
 
+  // Now that we're done, delete any instructions which are no longer used.
+  while (!DeadInsts.empty())
+    if (Instruction *Inst =
+          cast_or_null<Instruction>((Value *)DeadInsts.pop_back_val()))
+      RecursivelyDeleteTriviallyDeadInstructions(Inst);
+
   // We are done with the rank map.
   RankMap.clear();
   ValueRankMap.clear();
diff --git a/test/Transforms/Reassociate/crash.ll b/test/Transforms/Reassociate/crash.ll
index 6f21b66ed00..7a819422eab 100644
--- a/test/Transforms/Reassociate/crash.ll
+++ b/test/Transforms/Reassociate/crash.ll
@@ -42,3 +42,28 @@ define i32 @test3(i32 %Arg, i32 %x1, i32 %x2, i32 %x3) {
  %E = add i32 %D, %C
   ret i32 %E
 }
+
+
+; rdar://9096268
+define void @x66303361ae3f602889d1b7d0f86e5455(i8* %arg) nounwind {
+_:
+  br label %_33
+
+_33:                                              ; preds = %_33, %_
+  %tmp348 = load i8* %arg, align 1
+  %tmp349 = lshr i8 %tmp348, 7
+  %tmp350 = or i8 %tmp349, 42
+  %tmp351 = add i8 %tmp350, -42
+  %tmp352 = zext i8 %tmp351 to i32
+  %tmp358 = add i32 %tmp352, -501049439
+  %tmp359 = mul i32 %tmp358, %tmp358
+  %tmp360 = mul i32 %tmp352, %tmp352
+  %tmp361 = sub i32 %tmp359, %tmp360
+  %tmp362 = mul i32 %tmp361, -920056735
+  %tmp363 = add i32 %tmp362, 501049439
+  %tmp364 = add i32 %tmp362, -2000262972
+  %tmp365 = sub i32 %tmp363, %tmp364
+  %tmp366 = sub i32 -501049439, %tmp362
+  %tmp367 = add i32 %tmp365, %tmp366
+  br label %_33
+}
-- 
2.34.1