[LoopUnroll] Don't crash trying to unroll loop with EH pad exit

We do not support splitting cleanuppad or catchswitches.  This is
problematic for passes which assume that a loop is in loop simplify
form (the loop would have a dedicated exit block instead of sharing it).

While it isn't great that we don't support this for cleanups, we still
cannot make loop-simplify form an assertable precondition because
indirectbr will also disable these sorts of CFG cleanups.

This fixes PR28132.

llvm-svn: 272739

lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -922,6 +922,11 @@ static bool tryToUnrollLoop(Loop *L, DominatorTree &DT, LoopInfo *LI,
     DEBUG(dbgs() << "  Not unrolling loop with inlinable calls.\n");
     return false;
   }
+  if (!L->isLoopSimplifyForm()) {
+    DEBUG(
+        dbgs() << "  Not unrolling loop which is not in loop-simplify form.\n");
+    return false;
+  }
 
   // Find trip count and trip multiple if count is not available
   unsigned TripCount = 0;

test/Transforms/LoopUnroll/pr28132.ll

@@ -0,0 +1,77 @@
+; RUN: opt -loop-unroll -S < %s | FileCheck %s
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc"
+
+declare void @fn1(i8*)
+
+declare i1 @fn2(i8*, i8*)
+
+define void @fn4() personality i32 (...)* @__CxxFrameHandler3 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc, %entry
+  %i.05 = phi i8 [ 0, %entry ], [ %inc, %for.inc ]
+  store i8 undef, i8* undef, align 4
+  invoke void @fn1(i8* undef)
+          to label %call.i.noexc unwind label %ehcleanup
+
+call.i.noexc:                                     ; preds = %for.body
+  %call1.i2 = invoke i1 @fn2(i8* undef, i8* undef)
+          to label %call1.i.noexc unwind label %ehcleanup
+
+call1.i.noexc:                                    ; preds = %call.i.noexc
+  br i1 undef, label %if.then.i, label %if.end4.i
+
+if.then.i:                                        ; preds = %call1.i.noexc
+  %tmp1 = load i8, i8* undef, align 4
+  %tobool.i = icmp eq i8 undef, undef
+  br i1 undef, label %if.end4.i, label %if.then2.i
+
+if.then2.i:                                       ; preds = %if.then.i
+  %call3.i3 = invoke i1 @fn2(i8* undef, i8* null)
+          to label %call3.i.noexc unwind label %ehcleanup
+
+call3.i.noexc:                                    ; preds = %if.then2.i
+  br label %if.end4.i
+
+if.end4.i:                                        ; preds = %call3.i.noexc, %if.then.i, %call1.i.noexc
+  %tmp2 = load i8, i8* undef, align 4
+  br label %if.then6.i
+
+if.then6.i:                                       ; preds = %if.end4.i
+  %call7.i4 = invoke i1 @fn2(i8* undef, i8* null)
+          to label %call7.i.noexc unwind label %ehcleanup
+
+call7.i.noexc:                                    ; preds = %if.then6.i
+  br label %fn3
+
+fn3:                                              ; preds = %call7.i.noexc
+  %tmp3 = load i8, i8* undef, align 4
+  %inc.i = add nsw i8 undef, undef
+  store i8 undef, i8* undef, align 4
+  br label %for.inc
+
+for.inc:                                          ; preds = %fn3
+  %inc = add nsw i8 %i.05, 1
+  %cmp = icmp slt i8 %inc, 6
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc
+  invoke void @throw()
+          to label %unreachable unwind label %ehcleanup
+
+ehcleanup:                                        ; preds = %for.end, %if.then6.i, %if.then2.i, %call.i.noexc, %for.body
+  %cp = cleanuppad within none []
+  cleanupret from %cp unwind to caller
+
+; CHECK: cleanuppad
+; CHECK-NOT: cleanuppad
+
+unreachable:                                      ; preds = %for.end
+  unreachable
+}
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @throw()