Check whether IslAstInfo and DependenceInfo were computed for the same Scop.

Since -polly-codegen reports itself to preserve DependenceInfo and IslAstInfo,
we might get those analysis that were computed by a different ScopInfo for a
different Scop structure. This would be unfortunate because DependenceInfo and
IslAstInfo hold references to resources allocated by
ScopInfo/ScopBuilder/Scop (e.g. isl_id). If -polly-codegen and
DependenceInfo/IslAstInfo do not agree on which Scop to use, unpredictable
things can happen.

When the ScopInfo/Scop object is freed, there is a high probability that the
new ScopInfo/Scop object will be created at the same heap position with the
same address. Comparing whether the Scop or ScopInfo address is the expected
therefore is unreliable.

Instead, we compare the address of the isl_ctx object. Both, DependenceInfo
and IslAstInfo must hold a reference to the isl_ctx object to ensure it is
not freed before the destruction of those analyses which might happen after
the destruction of the Scop/ScopInfo they refer to.  Hence, the isl_ctx
will not be freed and its address not reused as long there is a
DependenceInfo or IslAstInfo around.

This fixes llvm.org/PR34441

llvm-svn: 313842

7 files changed, 101 insertions, 3 deletions

diff --git a/polly/include/polly/CodeGen/IslAst.h b/polly/include/polly/CodeGen/IslAst.h
index 79335be524b..c1d3305e430 100644
--- a/polly/include/polly/CodeGen/IslAst.h
+++ b/polly/include/polly/CodeGen/IslAst.h
@@ -67,6 +67,8 @@ public:
 
   __isl_give isl_ast_node *getAst();
 
+  const std::shared_ptr<isl_ctx> getSharedIslCtx() const { return Ctx; }
+
   /// Get the run-time conditions for the Scop.
   __isl_give isl_ast_expr *getRunCondition();
 
@@ -131,6 +133,9 @@ private:
 public:
   IslAstInfo(Scop &S, const Dependences &D) : S(S), Ast(IslAst::create(S, D)) {}
 
+  /// Return the isl AST computed by this IslAstInfo.
+  IslAst &getIslAst() { return Ast; }
+
   /// Return a copy of the AST root node.
   __isl_give isl_ast_node *getAst();
 
diff --git a/polly/include/polly/DependenceInfo.h b/polly/include/polly/DependenceInfo.h
index d440dd54e7f..89c3205a437 100644
--- a/polly/include/polly/DependenceInfo.h
+++ b/polly/include/polly/DependenceInfo.h
@@ -92,6 +92,8 @@ struct Dependences {
     TYPE_TC_RED = 1 << 4,
   };
 
+  const std::shared_ptr<isl_ctx> &getSharedIslCtx() const { return IslCtx; }
+
   /// Get the dependences of type @p Kinds.
   ///
   /// @param Kinds This integer defines the different kinds of dependences
diff --git a/polly/lib/CodeGen/CodeGeneration.cpp b/polly/lib/CodeGen/CodeGeneration.cpp
index 240ce23c1b4..41a3b2fcf6a 100644
--- a/polly/lib/CodeGen/CodeGeneration.cpp
+++ b/polly/lib/CodeGen/CodeGeneration.cpp
@@ -182,8 +182,27 @@ static void removeLifetimeMarkers(Region *R) {
 
 static bool CodeGen(Scop &S, IslAstInfo &AI, LoopInfo &LI, DominatorTree &DT,
                     ScalarEvolution &SE, RegionInfo &RI) {
+  // Check whether IslAstInfo uses the same isl_ctx. Since -polly-codegen
+  // reports itself to preserve DependenceInfo and IslAstInfo, we might get
+  // those analysis that were computed by a different ScopInfo for a different
+  // Scop structure. When the ScopInfo/Scop object is freed, there is a high
+  // probability that the new ScopInfo/Scop object will be created at the same
+  // heap position with the same address. Comparing whether the Scop or ScopInfo
+  // address is the expected therefore is unreliable.
+  // Instead, we compare the address of the isl_ctx object. Both, DependenceInfo
+  // and IslAstInfo must hold a reference to the isl_ctx object to ensure it is
+  // not freed before the destruction of those analyses which might happen after
+  // the destruction of the Scop/ScopInfo they refer to.  Hence, the isl_ctx
+  // will not be freed and its space not reused as long there is a
+  // DependenceInfo or IslAstInfo around.
+  IslAst &Ast = AI.getIslAst();
+  if (Ast.getSharedIslCtx() != S.getSharedIslCtx()) {
+    DEBUG(dbgs() << "Got an IstAst for a different Scop/isl_ctx\n");
+    return false;
+  }
+
   // Check if we created an isl_ast root node, otherwise exit.
-  isl_ast_node *AstRoot = AI.getAst();
+  isl_ast_node *AstRoot = Ast.getAst();
   if (!AstRoot)
     return false;
 
diff --git a/polly/lib/CodeGen/IslAst.cpp b/polly/lib/CodeGen/IslAst.cpp
index 3c67cc7ed10..346e14f496b 100644
--- a/polly/lib/CodeGen/IslAst.cpp
+++ b/polly/lib/CodeGen/IslAst.cpp
@@ -806,6 +806,12 @@ bool IslAstInfoWrapperPass::runOnScop(Scop &Scop) {
   const Dependences &D =
       getAnalysis<DependenceInfo>().getDependences(Dependences::AL_Statement);
 
+  if (D.getSharedIslCtx() != Scop.getSharedIslCtx()) {
+    DEBUG(dbgs() << "Got dependence analysis for different SCoP/isl_ctx\n");
+    Ast.reset();
+    return false;
+  }
+
   Ast.reset(new IslAstInfo(Scop, D));
 
   DEBUG(printScop(dbgs(), Scop));
@@ -815,7 +821,7 @@ bool IslAstInfoWrapperPass::runOnScop(Scop &Scop) {
 void IslAstInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   // Get the Common analysis usage of ScopPasses.
   ScopPass::getAnalysisUsage(AU);
-  AU.addRequired<ScopInfoRegionPass>();
+  AU.addRequiredTransitive<ScopInfoRegionPass>();
   AU.addRequired<DependenceInfo>();
 
   AU.addPreserved<DependenceInfo>();
diff --git a/polly/lib/Transform/ScheduleOptimizer.cpp b/polly/lib/Transform/ScheduleOptimizer.cpp
index 0a2fe8b6897..899f1c06830 100644
--- a/polly/lib/Transform/ScheduleOptimizer.cpp
+++ b/polly/lib/Transform/ScheduleOptimizer.cpp
@@ -1485,6 +1485,11 @@ bool IslScheduleOptimizer::runOnScop(Scop &S) {
   const Dependences &D =
       getAnalysis<DependenceInfo>().getDependences(Dependences::AL_Statement);
 
+  if (D.getSharedIslCtx() != S.getSharedIslCtx()) {
+    DEBUG(dbgs() << "DependenceInfo for another SCoP/isl_ctx\n");
+    return false;
+  }
+
   if (!D.hasValidDependences())
     return false;
 
diff --git a/polly/test/Isl/CodeGen/multiple-codegens.ll b/polly/test/Isl/CodeGen/multiple-codegens.ll
new file mode 100644
index 00000000000..b9bfb55e041
--- /dev/null
+++ b/polly/test/Isl/CodeGen/multiple-codegens.ll
@@ -0,0 +1,61 @@
+; RUN: opt %loadPolly -polly-scops -polly-opt-isl -polly-codegen -polly-scops -polly-codegen -S < %s | FileCheck %s
+;
+; llvm.org/PR34441
+; Properly handle multiple -polly-scops/-polly-codegen in the same
+; RegionPassManager. -polly-codegen must not reuse the -polly-ast analysis the
+; was created for the first -polly-scops pass.
+; The current solution is that only the first -polly-codegen is allowed to
+; generate code, the second detects it is re-using an IslAst that belongs to a
+; different ScopInfo.
+;
+; int a, b, c;
+;
+; int main () {
+;  while (a++)
+;    while (b) {
+;        c = 0;
+;        break;
+;      }
+;  return 0;
+; }
+;
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+
+@a = common global i32 0, align 4
+@b = common global i32 0, align 4
+@c = common global i32 0, align 4
+
+; Function Attrs: nounwind uwtable
+define i32 @main() {
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  %.pre = load i32, i32* @a, align 4
+  br label %while.cond
+
+while.cond:                                       ; preds = %while.end, %entry
+  %0 = phi i32 [ %inc, %while.end ], [ %.pre, %entry ]
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* @a, align 4
+  %tobool = icmp ne i32 %0, 0
+  br i1 %tobool, label %while.body, label %while.end4
+
+while.body:                                       ; preds = %while.cond
+  %1 = load i32, i32* @b, align 4
+  %tobool2 = icmp ne i32 %1, 0
+  br i1 %tobool2, label %while.body3, label %while.end
+
+while.body3:                                      ; preds = %while.body
+  store i32 0, i32* @c, align 4
+  br label %while.end
+
+while.end:                                        ; preds = %while.body3, %while.body
+  br label %while.cond
+
+while.end4:                                       ; preds = %while.cond
+  ret i32 0
+}
+
+
+; CHECK: polly.start:
+; CHECK-NOT: polly.start:
diff --git a/polly/test/ScopDetect/base_pointer_load_setNewAccessRelation.ll b/polly/test/ScopDetect/base_pointer_load_setNewAccessRelation.ll
index bc965526b4f..3561a49a271 100644
--- a/polly/test/ScopDetect/base_pointer_load_setNewAccessRelation.ll
+++ b/polly/test/ScopDetect/base_pointer_load_setNewAccessRelation.ll
@@ -1,4 +1,4 @@
-; RUN: opt %loadPolly -polly-ignore-aliasing -polly-invariant-load-hoisting=true -polly-import-jscop -polly-scops -polly-codegen -analyze < %s | FileCheck %s
+; RUN: opt %loadPolly -polly-ignore-aliasing -polly-invariant-load-hoisting=true -polly-scops -polly-import-jscop -polly-codegen -analyze < %s | FileCheck %s
 ;
 ; This violated an assertion in setNewAccessRelation that assumed base pointers
 ; to be load-hoisted. Without this assertion, it codegen would generate invalid