From 8ec94ead7d1cfa2afb907b465a5f9d960713e98f Mon Sep 17 00:00:00 2001
From: Kuba Brecka <kuba.brecka@gmail.com>
Date: Wed, 22 Jul 2015 10:25:38 +0000
Subject: [PATCH] [asan] Improve moving of non-instrumented allocas

In r242510, non-instrumented allocas are now moved into the first basic block.  This patch limits that to only move allocas that are present *after* the first instrumented one (i.e. only move allocas up).  A testcase was updated to show behavior in these two cases.  Without the patch, an alloca could be moved down, and could cause an invalid IR.

Differential Revision: http://reviews.llvm.org/D11339

llvm-svn: 242883
---
 .../Instrumentation/AddressSanitizer.cpp           | 18 ++++++++++------
 .../debug_info_noninstrumented_alloca.ll           | 25 ++++++++++++++++------
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index ed2de44..c7f3cfb 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -18,6 +18,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
@@ -538,7 +539,7 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   ShadowMapping Mapping;
 
   SmallVector<AllocaInst *, 16> AllocaVec;
-  SmallVector<AllocaInst *, 16> NonInstrumentedStaticAllocaVec;
+  SmallSetVector<AllocaInst *, 16> NonInstrumentedStaticAllocaVec;
   SmallVector<Instruction *, 8> RetVec;
   unsigned StackAlignment;
 
@@ -641,7 +642,7 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   /// \brief Collect Alloca instructions we want (and can) handle.
   void visitAllocaInst(AllocaInst &AI) {
     if (!ASan.isInterestingAlloca(AI)) {
-      if (AI.isStaticAlloca()) NonInstrumentedStaticAllocaVec.push_back(&AI);
+      if (AI.isStaticAlloca()) NonInstrumentedStaticAllocaVec.insert(&AI);
       return;
     }
 
@@ -1787,10 +1788,15 @@ void FunctionStackPoisoner::poisonStack() {
   IRBuilder<> IRB(InsBefore);
   IRB.SetCurrentDebugLocation(EntryDebugLocation);
 
-  // Make sure non-instrumented allocas stay in the first basic block.
-  // Otherwise, debug info is broken, because only first-basic-block allocas are
-  // treated as regular stack slots.
-  for (auto *AI : NonInstrumentedStaticAllocaVec) AI->moveBefore(InsBefore);
+  // Make sure non-instrumented allocas stay in the entry block. Otherwise,
+  // debug info is broken, because only entry-block allocas are treated as
+  // regular stack slots.
+  auto InsBeforeB = InsBefore->getParent();
+  assert(InsBeforeB == &F.getEntryBlock());
+  for (BasicBlock::iterator I = InsBefore; I != InsBeforeB->end(); ++I)
+    if (auto *AI = dyn_cast_or_null<AllocaInst>(I))
+      if (NonInstrumentedStaticAllocaVec.count(AI) > 0)
+        AI->moveBefore(InsBefore);
 
   // If we have a call to llvm.localescape, keep it in the entry block.
   if (LocalEscapeCall) LocalEscapeCall->moveBefore(InsBefore);
diff --git a/llvm/test/Instrumentation/AddressSanitizer/debug_info_noninstrumented_alloca.ll b/llvm/test/Instrumentation/AddressSanitizer/debug_info_noninstrumented_alloca.ll
index 7c38729f..844da79 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/debug_info_noninstrumented_alloca.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/debug_info_noninstrumented_alloca.ll
@@ -9,18 +9,31 @@ target triple = "x86_64-apple-macosx10.10.0"
 
 define i32 @foo() sanitize_address {
 entry:
+  ; Won't be instrumented because of asan-skip-promotable-allocas.
+  %non_instrumented1 = alloca i32, align 4
+
   ; Regular alloca, will get instrumented (forced by the ptrtoint below).
   %instrumented = alloca i32, align 4
 
   ; Won't be instrumented because of asan-skip-promotable-allocas.
-  %non_instrumented = alloca i32, align 4
-  store i32 0, i32* %non_instrumented, align 4
-  %value = load i32, i32* %non_instrumented, align 4
+  %non_instrumented2 = alloca i32, align 4
+
+  br label %bb0
+
+bb0:
+  ; Won't be instrumented because of asan-skip-promotable-allocas.
+  %non_instrumented3 = alloca i32, align 4
+
+  %ptr = ptrtoint i32* %instrumented to i32
+  br label %bb1
 
-  %ptr = ptrtoint i32* %instrumented to i64
-  ret i32 %value
+bb1:
+  ret i32 %ptr
 }
 
 ; CHECK: entry:
-; CHECK: %non_instrumented = alloca i32, align 4
+; CHECK: %non_instrumented1 = alloca i32, align 4
+; CHECK: %non_instrumented2 = alloca i32, align 4
 ; CHECK: load i32, i32* @__asan_option_detect_stack_use_after_return
+; CHECK: bb0:
+; CHECK: %non_instrumented3 = alloca i32, align 4
-- 
2.7.4