[llvm-commits] Workaround for PR1508

[Chris Lattner]

On Jun 13, 2007, at 10:55 AM, Duncan Sands wrote:

> Look for eh.filter and eh.selector intrinsics in the
> successor to an empty (exception for a branch) landing pad.
> The big FIXME comment explains more.  Testcase included,
> along with an XFAIL for a test which uses eh.selector in a
> routine with no landing pads (not possible in llvm-gcc
> generated code).

Seems fine to me, minor comments:

Please use SmallSet<CallInst*, 4> instead of std::set.

+  // Inform the MachineModuleInfo of the personality for this  
landing pad.
+  ConstantExpr *CE = dyn_cast<ConstantExpr>(I.getOperand(2));
+  assert(CE && CE->getOpcode() == Instruction::BitCast &&

Please just use cast<> instead of dyn_cast, which guarantees no null  
return.



+      if (Br && Br->isUnconditional() && LLVMBB->size() == 1) {
+        // Smells like a critical edge: look for eh intrinsics in  
the successor.
+        BasicBlock *S = Br->getSuccessor(0);
+
+        assert(!FuncInfo.MBBMap[S]->isLandingPad() &&
+               "Chained landing pads!");
+        for (BasicBlock::iterator I = S->begin(), E = --S->end(); I ! 
= E; ++I)
+          if (CallInst *C = dyn_cast<CallInst>(I))
+            if (Function *F = C->getCalledFunction())
+              if (F->isDeclaration())
+                if (unsigned IID = F->getIntrinsicID())
+                  if (IID == Intrinsic::eh_selector ||
+                      IID == Intrinsic::eh_filter) {
+                    addCatchInfo(*C, MMI, BB, IID ==  
Intrinsic::eh_filter);
+#ifndef NDEBUG
+                    FuncInfo.SelectorsFound.insert(C);
+#endif
+                  }

Please split this out into a helper predicate function.  Inside the  
loop, please use continue to avoid nesting so much:

if (!F->isDeclaration()) continue;
...
if (IID != .. && IID != ..) continue;

-Chris