Adding support for llvm.eh.begincatch and llvm.eh.endcatch intrinsics and beginning the documentation of native Windows exception handling.
Differential Revision: http://reviews.llvm.org/D7398
llvm-svn: 228733
diff --git a/llvm/lib/Analysis/Lint.cpp b/llvm/lib/Analysis/Lint.cpp
index 30a2666..beebb3b 100644
--- a/llvm/lib/Analysis/Lint.cpp
+++ b/llvm/lib/Analysis/Lint.cpp
@@ -35,6 +35,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Lint.h"
+#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
@@ -73,6 +74,8 @@
void visitMemoryReference(Instruction &I, Value *Ptr,
uint64_t Size, unsigned Align,
Type *Ty, unsigned Flags);
+ void visitEHBeginCatch(IntrinsicInst *II);
+ void visitEHEndCatch(IntrinsicInst *II);
void visitCallInst(CallInst &I);
void visitInvokeInst(InvokeInst &I);
@@ -346,6 +349,13 @@
visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
0, nullptr, MemRef::Read | MemRef::Write);
break;
+
+ case Intrinsic::eh_begincatch:
+ visitEHBeginCatch(II);
+ break;
+ case Intrinsic::eh_endcatch:
+ visitEHEndCatch(II);
+ break;
}
}
@@ -509,6 +519,188 @@
"Undefined result: Shift count out of range", &I);
}
+static bool
+allPredsCameFromLandingPad(BasicBlock *BB,
+ SmallSet<BasicBlock *, 4> &VisitedBlocks) {
+ VisitedBlocks.insert(BB);
+ if (BB->isLandingPad())
+ return true;
+ // If we find a block with no predecessors, the search failed.
+ if (pred_empty(BB))
+ return false;
+ for (BasicBlock *Pred : predecessors(BB)) {
+ if (VisitedBlocks.count(Pred))
+ continue;
+ if (!allPredsCameFromLandingPad(Pred, VisitedBlocks))
+ return false;
+ }
+ return true;
+}
+
+static bool
+allSuccessorsReachEndCatch(BasicBlock *BB, BasicBlock::iterator InstBegin,
+ IntrinsicInst **SecondBeginCatch,
+ SmallSet<BasicBlock *, 4> &VisitedBlocks) {
+ VisitedBlocks.insert(BB);
+ for (BasicBlock::iterator I = InstBegin, E = BB->end(); I != E; ++I) {
+ IntrinsicInst *IC = dyn_cast<IntrinsicInst>(I);
+ if (IC && IC->getIntrinsicID() == Intrinsic::eh_endcatch)
+ return true;
+ // If we find another begincatch while looking for an endcatch,
+ // that's also an error.
+ if (IC && IC->getIntrinsicID() == Intrinsic::eh_begincatch) {
+ *SecondBeginCatch = IC;
+ return false;
+ }
+ }
+
+ // If we reach a block with no successors while searching, the
+ // search has failed.
+ if (succ_empty(BB))
+ return false;
+ // Otherwise, search all of the successors.
+ for (BasicBlock *Succ : successors(BB)) {
+ if (VisitedBlocks.count(Succ))
+ continue;
+ if (!allSuccessorsReachEndCatch(Succ, Succ->begin(), SecondBeginCatch,
+ VisitedBlocks))
+ return false;
+ }
+ return true;
+}
+
+void Lint::visitEHBeginCatch(IntrinsicInst *II) {
+ // The checks in this function make a potentially dubious assumption about
+ // the CFG, namely that any block involved in a catch is only used for the
+ // catch. This will very likely be true of IR generated by a front end,
+ // but it may cease to be true, for example, if the IR is run through a
+ // pass which combines similar blocks.
+ //
+ // In general, if we encounter a block the isn't dominated by the catch
+ // block while we are searching the catch block's successors for a call
+ // to end catch intrinsic, then it is possible that it will be legal for
+ // a path through this block to never reach a call to llvm.eh.endcatch.
+ // An analogous statement could be made about our search for a landing
+ // pad among the catch block's predecessors.
+ //
+ // What is actually required is that no path is possible at runtime that
+ // reaches a call to llvm.eh.begincatch without having previously visited
+ // a landingpad instruction and that no path is possible at runtime that
+ // calls llvm.eh.begincatch and does not subsequently call llvm.eh.endcatch
+ // (mentally adjusting for the fact that in reality these calls will be
+ // removed before code generation).
+ //
+ // Because this is a lint check, we take a pessimistic approach and warn if
+ // the control flow is potentially incorrect.
+
+ SmallSet<BasicBlock *, 4> VisitedBlocks;
+ BasicBlock *CatchBB = II->getParent();
+
+ // The begin catch must occur in a landing pad block or all paths
+ // to it must have come from a landing pad.
+ Assert1(allPredsCameFromLandingPad(CatchBB, VisitedBlocks),
+ "llvm.eh.begincatch may be reachable without passing a landingpad",
+ II);
+
+ // Reset the visited block list.
+ VisitedBlocks.clear();
+
+ IntrinsicInst *SecondBeginCatch = nullptr;
+
+ // This has to be called before it is asserted. Otherwise, the first assert
+ // below can never be hit.
+ bool EndCatchFound = allSuccessorsReachEndCatch(
+ CatchBB, std::next(static_cast<BasicBlock::iterator>(II)),
+ &SecondBeginCatch, VisitedBlocks);
+ Assert2(
+ SecondBeginCatch == nullptr,
+ "llvm.eh.begincatch may be called a second time before llvm.eh.endcatch",
+ II, SecondBeginCatch);
+ Assert1(EndCatchFound,
+ "Some paths from llvm.eh.begincatch may not reach llvm.eh.endcatch",
+ II);
+}
+
+static bool allPredCameFromBeginCatch(
+ BasicBlock *BB, BasicBlock::reverse_iterator InstRbegin,
+ IntrinsicInst **SecondEndCatch, SmallSet<BasicBlock *, 4> &VisitedBlocks) {
+ VisitedBlocks.insert(BB);
+ // Look for a begincatch in this block.
+ for (BasicBlock::reverse_iterator RI = InstRbegin, RE = BB->rend(); RI != RE;
+ ++RI) {
+ IntrinsicInst *IC = dyn_cast<IntrinsicInst>(&*RI);
+ if (IC && IC->getIntrinsicID() == Intrinsic::eh_begincatch)
+ return true;
+ // If we find another end catch before we find a begin catch, that's
+ // an error.
+ if (IC && IC->getIntrinsicID() == Intrinsic::eh_endcatch) {
+ *SecondEndCatch = IC;
+ return false;
+ }
+ // If we encounter a landingpad instruction, the search failed.
+ if (isa<LandingPadInst>(*RI))
+ return false;
+ }
+ // If while searching we find a block with no predeccesors,
+ // the search failed.
+ if (pred_empty(BB))
+ return false;
+ // Search any predecessors we haven't seen before.
+ for (BasicBlock *Pred : predecessors(BB)) {
+ if (VisitedBlocks.count(Pred))
+ continue;
+ if (!allPredCameFromBeginCatch(Pred, Pred->rbegin(), SecondEndCatch,
+ VisitedBlocks))
+ return false;
+ }
+ return true;
+}
+
+void Lint::visitEHEndCatch(IntrinsicInst *II) {
+ // The check in this function makes a potentially dubious assumption about
+ // the CFG, namely that any block involved in a catch is only used for the
+ // catch. This will very likely be true of IR generated by a front end,
+ // but it may cease to be true, for example, if the IR is run through a
+ // pass which combines similar blocks.
+ //
+ // In general, if we encounter a block the isn't post-dominated by the
+ // end catch block while we are searching the end catch block's predecessors
+ // for a call to the begin catch intrinsic, then it is possible that it will
+ // be legal for a path to reach the end catch block without ever having
+ // called llvm.eh.begincatch.
+ //
+ // What is actually required is that no path is possible at runtime that
+ // reaches a call to llvm.eh.endcatch without having previously visited
+ // a call to llvm.eh.begincatch (mentally adjusting for the fact that in
+ // reality these calls will be removed before code generation).
+ //
+ // Because this is a lint check, we take a pessimistic approach and warn if
+ // the control flow is potentially incorrect.
+
+ BasicBlock *EndCatchBB = II->getParent();
+
+ // Alls paths to the end catch call must pass through a begin catch call.
+
+ // If llvm.eh.begincatch wasn't called in the current block, we'll use this
+ // lambda to recursively look for it in predecessors.
+ SmallSet<BasicBlock *, 4> VisitedBlocks;
+ IntrinsicInst *SecondEndCatch = nullptr;
+
+ // This has to be called before it is asserted. Otherwise, the first assert
+ // below can never be hit.
+ bool BeginCatchFound =
+ allPredCameFromBeginCatch(EndCatchBB, BasicBlock::reverse_iterator(II),
+ &SecondEndCatch, VisitedBlocks);
+ Assert2(
+ SecondEndCatch == nullptr,
+ "llvm.eh.endcatch may be called a second time after llvm.eh.begincatch",
+ II, SecondEndCatch);
+ Assert1(
+ BeginCatchFound,
+ "llvm.eh.endcatch may be reachable without passing llvm.eh.begincatch",
+ II);
+}
+
static bool isZero(Value *V, const DataLayout *DL, DominatorTree *DT,
AssumptionCache *AC) {
// Assume undef could be zero.