[llvm] r277068 - Do not remove empty lifetime.start/lifetime.end ranges

[Vitaly Buka via llvm-commits]

Author: vitalybuka
Date: Thu Jul 28 17:50:48 2016
New Revision: 277068

URL: http://llvm.org/viewvc/llvm-project?rev=277068&view=rev
Log:
Do not remove empty lifetime.start/lifetime.end ranges

Summary:
Asan stack-use-after-scope check should poison alloca even if there is
no access between start and end.

This is possible for code like this:
for (int i = 0; i < 3; i++) {
  int x;
  p = &x;
}

"Loop Invariant Code Motion" will move "p = &x;" out of the loop, making
start/end range empty.

PR27453

Reviewers: eugenis

Differential Revision: https://reviews.llvm.org/D22842

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/lifetime-asan.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=277068&r1=277067&r2=277068&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Thu Jul 28 17:50:48 2016
@@ -30,8 +30,6 @@ using namespace PatternMatch;
 
 STATISTIC(NumSimplified, "Number of library calls simplified");
 
-extern cl::opt<bool> ClUseAfterScope;
-
 /// Return the specified type promoted as it would be to pass though a va_arg
 /// area.
 static Type *getPromotedType(Type *Ty) {
@@ -2244,18 +2242,16 @@ Instruction *InstCombiner::visitCallInst
       return eraseInstFromFunction(CI);
     break;
   }
-  case Intrinsic::lifetime_start: {
-    const Function *func = II->getFunction();
-    // Asan needs to poison memory to detect invalid access possible even for
-    // empty lifetime range.
-    if (func && func->hasFnAttribute(Attribute::SanitizeAddress))
+  case Intrinsic::lifetime_start:
+    // Asan needs to poison memory to detect invalid access which is possible
+    // even for empty lifetime range.
+    if (II->getFunction()->hasFnAttribute(Attribute::SanitizeAddress))
       break;
 
     if (removeTriviallyEmptyRange(*II, Intrinsic::lifetime_start,
                                   Intrinsic::lifetime_end, *this))
       return nullptr;
     break;
-  }
   case Intrinsic::assume: {
     Value *IIOperand = II->getArgOperand(0);
     // Remove an assume if it is immediately followed by an identical assume.
@@ -2486,6 +2482,7 @@ static IntrinsicInst *findInitTrampoline
 
 /// Improvements for call and invoke instructions.
 Instruction *InstCombiner::visitCallSite(CallSite CS) {
+
   if (isAllocLikeFn(CS.getInstruction(), TLI))
     return visitAllocSite(*CS.getInstruction());
 

Modified: llvm/trunk/test/Transforms/InstCombine/lifetime-asan.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/lifetime-asan.ll?rev=277068&r1=277067&r2=277068&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/lifetime-asan.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/lifetime-asan.ll Thu Jul 28 17:50:48 2016
@@ -7,15 +7,14 @@ declare void @foo(i8* nocapture)
 define void @asan() sanitize_address {
 entry:
   ; CHECK-LABEL: @asan(
-  %text = alloca [1 x i8], align 1
-  %0 = getelementptr inbounds [1 x i8], [1 x i8]* %text, i64 0, i64 0
+  %text = alloca i8, align 1
 
-  call void @llvm.lifetime.start(i64 1, i8* %0)
-  call void @llvm.lifetime.end(i64 1, i8* %0)
+  call void @llvm.lifetime.start(i64 1, i8* %text)
+  call void @llvm.lifetime.end(i64 1, i8* %text)
   ; CHECK: call void @llvm.lifetime.start
   ; CHECK-NEXT: call void @llvm.lifetime.end
 
-  call void @foo(i8* %0) ; Keep alloca alive
+  call void @foo(i8* %text) ; Keep alloca alive
 
   ret void
 }
@@ -24,14 +23,13 @@ entry:
 define void @no_asan() {
 entry:
   ; CHECK-LABEL: @no_asan(
-  %text = alloca [1 x i8], align 1
-  %0 = getelementptr inbounds [1 x i8], [1 x i8]* %text, i64 0, i64 0
+  %text = alloca i8, align 1
 
-  call void @llvm.lifetime.start(i64 1, i8* %0)
-  call void @llvm.lifetime.end(i64 1, i8* %0)
+  call void @llvm.lifetime.start(i64 1, i8* %text)
+  call void @llvm.lifetime.end(i64 1, i8* %text)
   ; CHECK-NO: call void @llvm.lifetime
 
-  call void @foo(i8* %0) ; Keep alloca alive
+  call void @foo(i8* %text) ; Keep alloca alive
 
   ret void
 }