From: Nadav Rotem <nrotem@apple.com>
Date: Thu, 13 Sep 2012 15:46:30 +0000 (+0000)
Subject: Rename the flag which protects from escaped allocas, which may come from bugs in... 
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=18e2c290940b67c9dc1196e3c2234e7a20f60ae4;p=oota-llvm.git

Rename the flag which protects from escaped allocas, which may come from bugs in user code or in the compiler. Also, dont assert if the protection is not enabled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163807 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/StackColoring.cpp b/lib/CodeGen/StackColoring.cpp
index 832d4d1ca5d..e9695b91e1a 100644
--- a/lib/CodeGen/StackColoring.cpp
+++ b/lib/CodeGen/StackColoring.cpp
@@ -62,10 +62,15 @@ DisableColoring("no-stack-coloring",
         cl::init(false), cl::Hidden,
         cl::desc("Disable stack coloring"));
 
+
+/// The user may write code that uses allocas outside of the declared lifetime
+/// zone. This can happen when the user returns a reference to a local
+/// data-structure. We can detect these cases and decide not to optimize the
+/// code. If this flag is enabled, we try to save the user.
 static cl::opt<bool>
-CheckEscapedAllocas("stack-coloring-check-escaped",
+ProtectFromEscapedAllocas("protect-from-escaped-allocas",
         cl::init(true), cl::Hidden,
-        cl::desc("Look for allocas which escaped the lifetime region"));
+        cl::desc("Do not optimize lifetime zones that are broken"));
 
 STATISTIC(NumMarkerSeen,  "Number of lifetime markers found.");
 STATISTIC(StackSpaceSaved, "Number of bytes saved due to merging slots.");
@@ -536,13 +541,15 @@ void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
         // In a debug build, check that the instruction that we are modifying is
         // inside the expected live range. If the instruction is not inside
         // the calculated range then it means that the alloca usage moved
-        // outside of the lifetime markers.
+        // outside of the lifetime markers, or that the user has a bug.
         // NOTE: Alloca address calculations which happen outside the lifetime
         // zone are are okay, despite the fact that we don't have a good way
         // for validating all of the usages of the calculation.
 #ifndef NDEBUG
         bool TouchesMemory = I->mayLoad() || I->mayStore();
-        if (!I->isDebugValue() && TouchesMemory) {
+        // If we *don't* protect the user from escaped allocas, don't bother
+        // validating the instructions.
+        if (!I->isDebugValue() && TouchesMemory && ProtectFromEscapedAllocas) {
           SlotIndex Index = Indexes->getInstructionIndex(I);
           LiveInterval *Interval = Intervals[FromSlot];
           assert(Interval->find(Index) != Interval->end() &&
@@ -685,7 +692,7 @@ bool StackColoring::runOnMachineFunction(MachineFunction &Func) {
 
   // Search for allocas which are used outside of the declared lifetime
   // markers.
-  if (CheckEscapedAllocas)
+  if (ProtectFromEscapedAllocas)
     removeInvalidSlotRanges();
 
   // Maps old slots to new slots.