From: Chris Lattner <sabre@nondot.org>
Date: Fri, 18 Feb 2011 04:43:06 +0000 (+0000)
Subject: prevent jump threading from merging blocks when their address is
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=78f7a25f9826ba66610b5bca83ebea71793abf59;p=oota-llvm.git

prevent jump threading from merging blocks when their address is
taken (and used!).  This prevents merging the blocks (invalidating
the block addresses) in a case like this:

#define _THIS_IP_  ({ __label__ __here; __here: (unsigned long)&&__here; })

void foo() {
  printf("%p\n", _THIS_IP_);
  printf("%p\n", _THIS_IP_);
  printf("%p\n", _THIS_IP_);
}

which fixes PR4151.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125829 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 3d218a6585a..90094a8da25 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -606,6 +606,16 @@ static unsigned GetBestDestForJumpOnUndef(BasicBlock *BB) {
   return MinSucc;
 }
 
+static bool hasAddressTakenAndUsed(BasicBlock *BB) {
+  if (!BB->hasAddressTaken()) return false;
+  
+  // If the block has its address taken, it may be a tree of dead constants
+  // hanging off of it.  These shouldn't keep the block alive.
+  BlockAddress *BA = BlockAddress::get(BB);
+  BA->removeDeadConstantUsers();
+  return !BA->use_empty();
+}
+
 /// ProcessBlock - If there are any predecessors whose control can be threaded
 /// through to a successor, transform them now.
 bool JumpThreading::ProcessBlock(BasicBlock *BB) {
@@ -621,7 +631,7 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
   // predecessors of our predecessor block.
   if (BasicBlock *SinglePred = BB->getSinglePredecessor()) {
     if (SinglePred->getTerminator()->getNumSuccessors() == 1 &&
-        SinglePred != BB) {
+        SinglePred != BB && !hasAddressTakenAndUsed(BB)) {
       // If SinglePred was a loop header, BB becomes one.
       if (LoopHeaders.erase(SinglePred))
         LoopHeaders.insert(BB);
diff --git a/test/Transforms/JumpThreading/indirectbr.ll b/test/Transforms/JumpThreading/indirectbr.ll
index 6c5321d3194..141277fec62 100644
--- a/test/Transforms/JumpThreading/indirectbr.ll
+++ b/test/Transforms/JumpThreading/indirectbr.ll
@@ -44,7 +44,9 @@ indirectgoto:                                     ; preds = %if.else, %entry
 ; Check constant folding of indirectbr
 
 ; CHECK: void @test2
-; CHECK-NEXT: :
+; CHECK: entry:
+; CHECK-NEXT: br label %L1
+; CHECK: L1:
 ; CHECK-NEXT: call void @bar
 ; CHECK-NEXT: ret void
 define void @test2() nounwind {
@@ -59,3 +61,34 @@ L2:                                               ; preds = %indirectgoto
   call void @baz()
   ret void
 }
+
+
+; PR4151
+; Don't merge address-taken blocks.
+@.str = private unnamed_addr constant [4 x i8] c"%p\0A\00"
+
+; CHECK: @test3
+; CHECK: __here:
+; CHECK: blockaddress(@test3, %__here)
+; CHECK: __here1:
+; CHECK: blockaddress(@test3, %__here1)
+; CHECK: __here3:
+; CHECK: blockaddress(@test3, %__here3)
+define void @test3() nounwind ssp noredzone {
+entry:
+  br label %__here
+
+__here:                                           ; preds = %entry
+  %call = call i32 (...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i64 ptrtoint (i8* blockaddress(@test3, %__here) to i64)) nounwind noredzone
+  br label %__here1
+
+__here1:                                          ; preds = %__here
+  %call2 = call i32 (...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i64 ptrtoint (i8* blockaddress(@test3, %__here1) to i64)) nounwind noredzone
+  br label %__here3
+
+__here3:                                          ; preds = %__here1
+  %call4 = call i32 (...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i64 ptrtoint (i8* blockaddress(@test3, %__here3) to i64)) nounwind noredzone
+  ret void
+}
+
+declare i32 @printf(...) noredzone