From 0a16da445740ca6fcd7a7ca571c1917e77315904 Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Wed, 12 Sep 2012 04:57:37 +0000
Subject: [PATCH] Stack coloring: remove lifetime intervals which contain
 escaped allocas.

The input program may contain intructions which are not inside lifetime
markers. This can happen due to a bug in the compiler or due to a bug in
user code (for example, returning a reference to a local variable).
This commit adds checks that all of the instructions in the function and
invalidates lifetime ranges which do not contain all of the instructions.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163678 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/StackColoring.cpp     | 47 +++++++++++++++++++++++++++++++
 test/CodeGen/X86/StackColoring.ll | 30 ++++++++++++++++++--
 2 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/lib/CodeGen/StackColoring.cpp b/lib/CodeGen/StackColoring.cpp
index 6df932c1ae0..16b715a7962 100644
--- a/lib/CodeGen/StackColoring.cpp
+++ b/lib/CodeGen/StackColoring.cpp
@@ -158,6 +158,14 @@ private:
   /// slots to use the joint slots.
   void remapInstructions(DenseMap<int, int> &SlotRemap);
 
+  /// The input program may contain intructions which are not inside lifetime
+  /// markers. This can happen due to a bug in the compiler or due to a bug in
+  /// user code (for example, returning a reference to a local variable).
+  /// This procedure checks all of the instructions in the function and
+  /// invalidates lifetime ranges which do not contain all of the instructions
+  /// which access that frame slot.
+  void removeInvalidSlotRanges();
+
   /// Map entries which point to other entries to their destination.
   ///   A->B->C becomes A->C.
    void expungeSlotMap(DenseMap<int, int> &SlotRemap, unsigned NumSlots);
@@ -543,6 +551,43 @@ void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
   DEBUG(dbgs()<<"Fixed "<<FixedInstr<<" machine instructions.\n");
 }
 
+void StackColoring::removeInvalidSlotRanges() {
+  MachineFunction::iterator BB, BBE;
+  MachineBasicBlock::iterator I, IE;
+  for (BB = MF->begin(), BBE = MF->end(); BB != BBE; ++BB)
+    for (I = BB->begin(), IE = BB->end(); I != IE; ++I) {
+
+      if (I->getOpcode() == TargetOpcode::LIFETIME_START ||
+          I->getOpcode() == TargetOpcode::LIFETIME_END || I->isDebugValue())
+        continue;
+
+      // Check all of the machine operands.
+      for (unsigned i = 0 ; i <  I->getNumOperands(); ++i) {
+        MachineOperand &MO = I->getOperand(i);
+
+        if (!MO.isFI())
+          continue;
+
+        int Slot = MO.getIndex();
+
+        if (Slot<0)
+          continue;
+
+        if (Intervals[Slot]->empty())
+          continue;
+
+        // Check that the used slot is inside the calculated lifetime range.
+        // If it is not, warn about it and invalidate the range.
+        LiveInterval *Interval = Intervals[Slot];
+        SlotIndex Index = Indexes->getInstructionIndex(I);
+        if (Interval->find(Index) == Interval->end()) {
+          Intervals[Slot]->clear();
+          DEBUG(dbgs()<<"Invalidating range #"<<Slot<<"\n");
+        }
+      }
+    }
+}
+
 void StackColoring::expungeSlotMap(DenseMap<int, int> &SlotRemap,
                                    unsigned NumSlots) {
   // Expunge slot remap map.
@@ -617,6 +662,8 @@ bool StackColoring::runOnMachineFunction(MachineFunction &Func) {
   // Propagate the liveness information.
   calculateLiveIntervals(NumSlots);
 
+  removeInvalidSlotRanges();
+
   // Maps old slots to new slots.
   DenseMap<int, int> SlotRemap;
   unsigned RemovedSlots = 0;
diff --git a/test/CodeGen/X86/StackColoring.ll b/test/CodeGen/X86/StackColoring.ll
index 0f36ce29b9a..a83a4ebbe2e 100644
--- a/test/CodeGen/X86/StackColoring.ll
+++ b/test/CodeGen/X86/StackColoring.ll
@@ -7,7 +7,6 @@ target triple = "x86_64-apple-macosx10.8.0"
 ;YESCOLOR: subq  $136, %rsp
 ;NOCOLOR: subq  $264, %rsp
 
-
 define i32 @myCall_w2(i32 %in) {
 entry:
   %a = alloca [17 x i8*], align 8
@@ -328,7 +327,6 @@ entry:
 
 ;YESCOLOR: subq  $272, %rsp
 ;NOCOLOR: subq  $272, %rsp
-
 define i32 @myCall_end_before_begin(i32 %in, i1 %d) {
 entry:
   %a = alloca [17 x i8*], align 8
@@ -352,11 +350,37 @@ bb3:
   ret i32 0
 }
 
+; Check that we don't assert and crash even when there are allocas
+; outside the declared lifetime regions.
+;YESCOLOR: bad_range
+;NOCOLOR:  bad_range
+define void @bad_range() nounwind ssp {
+entry:
+  %A.i1 = alloca [100 x i32], align 4
+  %B.i2 = alloca [100 x i32], align 4
+  %A.i = alloca [100 x i32], align 4
+  %B.i = alloca [100 x i32], align 4
+  %0 = bitcast [100 x i32]* %A.i to i8*
+  call void @llvm.lifetime.start(i64 -1, i8* %0) nounwind
+  %1 = bitcast [100 x i32]* %B.i to i8*
+  call void @llvm.lifetime.start(i64 -1, i8* %1) nounwind
+  call void @bar([100 x i32]* %A.i, [100 x i32]* %B.i) nounwind
+  call void @llvm.lifetime.end(i64 -1, i8* %0) nounwind
+  call void @llvm.lifetime.end(i64 -1, i8* %1) nounwind
+  br label %block2
+
+block2:
+  ; I am used outside the marked lifetime.
+  call void @bar([100 x i32]* %A.i, [100 x i32]* %B.i) nounwind
+  ret void
+}
+
+
 declare void @bar([100 x i32]* , [100 x i32]*) nounwind
 
 declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
 
 declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind
 
- declare i32 @foo(i32, i8*)
+declare i32 @foo(i32, i8*)
 
-- 
2.34.1