[StackSafety] Skip ambiguous lifetime analysis

If we can't identify alloca used in lifetime marker we
need to assume to worst case scenario.

Reviewed By: eugenis

Differential Revision: https://reviews.llvm.org/D84630

diff --git a/llvm/include/llvm/Analysis/StackLifetime.h b/llvm/include/llvm/Analysis/StackLifetime.h
index 8abc6cc..1c0e103 100644 (file)
--- a/llvm/include/llvm/Analysis/StackLifetime.h
+++ b/llvm/include/llvm/Analysis/StackLifetime.h
@@ -121,6 +121,8 @@ private:
   DenseMap<const BasicBlock *, SmallVector<std::pair<unsigned, Marker>, 4>>
       BBMarkers;
 
+  bool HasUnknownLifetimeStartOrEnd = false;
+
   void dumpAllocas() const;
   void dumpBlockLiveness() const;
   void dumpLiveRanges() const;

diff --git a/llvm/lib/Analysis/StackLifetime.cpp b/llvm/lib/Analysis/StackLifetime.cpp
index 9727b7a..ef8103f 100644 (file)
--- a/llvm/lib/Analysis/StackLifetime.cpp
+++ b/llvm/lib/Analysis/StackLifetime.cpp
@@ -11,6 +11,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/IR/AssemblyAnnotationWriter.h"
 #include "llvm/IR/BasicBlock.h"
@@ -63,42 +64,30 @@ bool StackLifetime::isAliveAfter(const AllocaInst *AI,
   return getLiveRange(AI).test(InstNum);
 }
 
-static bool readMarker(const Instruction *I, bool *IsStart) {
-  if (!I->isLifetimeStartOrEnd())
-    return false;
-
-  auto *II = cast<IntrinsicInst>(I);
-  *IsStart = II->getIntrinsicID() == Intrinsic::lifetime_start;
-  return true;
-}
-
 void StackLifetime::collectMarkers() {
   InterestingAllocas.resize(NumAllocas);
   DenseMap<const BasicBlock *, SmallDenseMap<const IntrinsicInst *, Marker>>
       BBMarkerSet;
 
   // Compute the set of start/end markers per basic block.
-  for (unsigned AllocaNo = 0; AllocaNo < NumAllocas; ++AllocaNo) {
-    const AllocaInst *AI = Allocas[AllocaNo];
-    SmallVector<const Instruction *, 8> WorkList;
-    WorkList.push_back(AI);
-    while (!WorkList.empty()) {
-      const Instruction *I = WorkList.pop_back_val();
-      for (const User *U : I->users()) {
-        if (auto *BI = dyn_cast<BitCastInst>(U)) {
-          WorkList.push_back(BI);
-          continue;
-        }
-        auto *UI = dyn_cast<IntrinsicInst>(U);
-        if (!UI)
-          continue;
-        bool IsStart;
-        if (!readMarker(UI, &IsStart))
-          continue;
-        if (IsStart)
-          InterestingAllocas.set(AllocaNo);
-        BBMarkerSet[UI->getParent()][UI] = {AllocaNo, IsStart};
+  for (const BasicBlock *BB : depth_first(&F)) {
+    for (const Instruction &I : *BB) {
+      const IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
+      if (!II || !II->isLifetimeStartOrEnd())
+        continue;
+      const AllocaInst *AI = llvm::findAllocaForValue(II->getArgOperand(1));
+      if (!AI) {
+        HasUnknownLifetimeStartOrEnd = true;
+        continue;
       }
+      auto It = AllocaNumbering.find(AI);
+      if (It == AllocaNumbering.end())
+        continue;
+      auto AllocaNo = It->second;
+      bool IsStart = II->getIntrinsicID() == Intrinsic::lifetime_start;
+      if (IsStart)
+        InterestingAllocas.set(AllocaNo);
+      BBMarkerSet[BB][II] = {AllocaNo, IsStart};
     }
   }
 
@@ -304,6 +293,20 @@ StackLifetime::StackLifetime(const Function &F,
 }
 
 void StackLifetime::run() {
+  if (HasUnknownLifetimeStartOrEnd) {
+    // There is marker which we can't assign to a specific alloca, so we
+    // fallback to the most conservative results for the type.
+    switch (Type) {
+    case LivenessType::May:
+      LiveRanges.resize(NumAllocas, getFullLiveRange());
+      break;
+    case LivenessType::Must:
+      LiveRanges.resize(NumAllocas, LiveRange(Instructions.size()));
+      break;
+    }
+    return;
+  }
+
   LiveRanges.resize(NumAllocas, LiveRange(Instructions.size()));
   for (unsigned I = 0; I < NumAllocas; ++I)
     if (!InterestingAllocas.test(I))

diff --git a/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll b/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
index 1c7eeb5..470450a 100644 (file)
--- a/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
+++ b/llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll
@@ -742,7 +742,7 @@ if.end:
 ; MAY-NEXT: Alive: <x y>
 ; MUST-NEXT: Alive: <y>
 
-ret void
+  ret void
 }
 
 define void @unreachable() {
@@ -778,7 +778,62 @@ end:
 ; CHECK: end:
 ; CHECK-NEXT: Alive: <x y>
 
-ret void
+  ret void
+}
+
+define void @non_alloca(i8* %p) {
+; CHECK-LABEL: define void @non_alloca
+entry:
+; CHECK: entry:
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+  %x = alloca i8, align 4
+  %y = alloca i8, align 4
+
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* %p)
+; CHECK: call void @llvm.lifetime.start.p0i8(i64 4, i8* %p)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* %x)
+; CHECK: call void @llvm.lifetime.start.p0i8(i64 4, i8* %x)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* %p)
+; CHECK: call void @llvm.lifetime.end.p0i8(i64 4, i8* %p)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  ret void
+}
+
+define void @select_alloca(i1 %v) {
+; CHECK-LABEL: define void @select_alloca
+entry:
+; CHECK: entry:
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+  %x = alloca i8, align 4
+  %y = alloca i8, align 4
+  %cxcy = select i1 %v, i8* %x, i8* %y
+
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* %cxcy)
+; CHECK: call void @llvm.lifetime.start.p0i8(i64 1, i8* %cxcy)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* %x)
+; CHECK: call void @llvm.lifetime.start.p0i8(i64 1, i8* %x)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  call void @llvm.lifetime.end.p0i8(i64 1, i8* %x)
+; CHECK: call void @llvm.lifetime.end.p0i8(i64 1, i8* %x)
+; MAY-NEXT: Alive: <x y>
+; MUST-NEXT: Alive: <>
+
+  ret void
 }
 
 declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)

diff --git a/llvm/test/CodeGen/AArch64/stack-tagging.ll b/llvm/test/CodeGen/AArch64/stack-tagging.ll
index 275b8a7..83fe402 100644 (file)
--- a/llvm/test/CodeGen/AArch64/stack-tagging.ll
+++ b/llvm/test/CodeGen/AArch64/stack-tagging.ll
@@ -192,10 +192,9 @@ another_bb:
 ; CHECK: alloca { i32, [12 x i8] }, align 16
 ; CHECK: call { i32, [12 x i8] }* @llvm.aarch64.tagp
 ; CHECK: call void @llvm.aarch64.settag(
-; SSI: alloca i32, align 4
-; NOSSI: alloca { i32, [12 x i8] }, align 16
-; NOSSI: call { i32, [12 x i8] }* @llvm.aarch64.tagp
-; NOSSI: call void @llvm.aarch64.settag(
+; CHECK: alloca { i32, [12 x i8] }, align 16
+; CHECK: call { i32, [12 x i8] }* @llvm.aarch64.tagp
+; CHECK: call void @llvm.aarch64.settag(
 ; CHECK: store i32
 ; CHECK: call void @noUse32(i32*
 ; CHECK: store i32
@@ -203,7 +202,7 @@ another_bb:
 ; CHECK: call void @noUse32(i32*
 ; CHECK: call void @llvm.aarch64.settag(
 ; CHECK: call void @llvm.aarch64.settag(
-; NOSSI: call void @llvm.aarch64.settag(
+; CHECK: call void @llvm.aarch64.settag(
 ; CHECK: ret void
 
-!0 = !{}
\ No newline at end of file
+!0 = !{}

diff --git a/llvm/test/Transforms/SafeStack/X86/no-crash-on-lifetime.ll b/llvm/test/Transforms/SafeStack/X86/no-crash-on-lifetime.ll
new file mode 100644 (file)
index 0000000..ee42618
--- /dev/null
+++ b/llvm/test/Transforms/SafeStack/X86/no-crash-on-lifetime.ll
@@ -0,0 +1,16 @@
+; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o -d
+
+%class.F = type { %class.o, i8, [7 x i8] }
+%class.o = type <{ i8*, i32, [4 x i8] }>
+
+define dso_local void @_ZN1s1tE1F(%class.F* byval(%class.F) %g) local_unnamed_addr safestack align 32 {
+entry:
+  %ref.tmp.i.i.i = alloca i64, align 1
+  call void undef(%class.F* %g)
+  %ref.tmp.i.i.0..sroa_idx.i5 = bitcast i64* %ref.tmp.i.i.i to i8*
+  call void @llvm.lifetime.start.p0i8(i64 3, i8* %ref.tmp.i.i.0..sroa_idx.i5)
+  ret void
+}
+
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1
+