Make Loop::getLoopLatch() work on loops which don't have preheaders, as

it may be used in contexts where preheader insertion may have failed due
to an indirectbr.

Make LoopSimplify's LoopSimplify::SeparateNestedLoop properly fail in
the case that it would require splitting an indirectbr edge.

These fix PR5502.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89484 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopInfo.h

@@ -269,8 +269,6 @@ public:
 
   /// getLoopLatch - If there is a single latch block for this loop, return it.
   /// A latch block is a block that contains a branch back to the header.
-  /// A loop header in normal form has two edges into it: one from a preheader
-  /// and one from a latch block.
   BlockT *getLoopLatch() const {
     BlockT *Header = getHeader();
     typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
@@ -278,20 +276,12 @@ public:
                                             InvBlockTraits::child_begin(Header);
     typename InvBlockTraits::ChildIteratorType PE =
                                               InvBlockTraits::child_end(Header);
-    if (PI == PE) return 0;  // no preds?
-
     BlockT *Latch = 0;
-    if (contains(*PI))
-      Latch = *PI;
-    ++PI;
-    if (PI == PE) return 0;  // only one pred?
-
-    if (contains(*PI)) {
-      if (Latch) return 0;  // multiple backedges
-      Latch = *PI;
-    }
-    ++PI;
-    if (PI != PE) return 0;  // more than two preds
+    for (; PI != PE; ++PI)
+      if (contains(*PI)) {
+        if (Latch) return 0;
+        Latch = *PI;
+      }
 
     return Latch;
   }

lib/Transforms/Utils/LoopSimplify.cpp

@@ -477,8 +477,13 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
   SmallVector<BasicBlock*, 8> OuterLoopPreds;
   for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
     if (PN->getIncomingValue(i) != PN ||
-        !L->contains(PN->getIncomingBlock(i)))
+        !L->contains(PN->getIncomingBlock(i))) {
+      // We can't split indirectbr edges.
+      if (isa<IndirectBrInst>(PN->getIncomingBlock(i)->getTerminator()))
+        return 0;
+
       OuterLoopPreds.push_back(PN->getIncomingBlock(i));
+    }
 
   BasicBlock *Header = L->getHeader();
   BasicBlock *NewBB = SplitBlockPredecessors(Header, &OuterLoopPreds[0],

test/Transforms/LoopRotate/indirectbr.ll

@@ -0,0 +1,43 @@
+; RUN: opt < %s -S -loop-rotate -disable-output -verify-loop-info -verify-dom-info
+; PR5502
+
+define void @z80_do_opcodes() nounwind {
+entry:
+  br label %while.cond
+
+while.cond:                                       ; preds = %end_opcode, %entry
+  br label %while.body
+
+while.body:                                       ; preds = %while.cond
+  br label %indirectgoto
+
+run_opcode:                                       ; preds = %indirectgoto
+  %tmp276 = load i8* undef                        ; <i8> [#uses=1]
+  br label %indirectgoto
+
+if.else295:                                       ; preds = %divide_late
+  br label %end_opcode
+
+end_opcode:                                       ; preds = %indirectgoto, %sw.default42406, %sw.default, %if.else295
+  %opcode.2 = phi i8 [ %opcode.0, %indirectgoto ], [ 0, %sw.default42406 ], [ undef, %sw.default ], [ %opcode.0, %if.else295 ] ; <i8> [#uses=0]
+  switch i32 undef, label %while.cond [
+    i32 221, label %sw.bb11691
+    i32 253, label %sw.bb30351
+  ]
+
+sw.bb11691:                                       ; preds = %end_opcode
+  br label %sw.default
+
+sw.default:                                       ; preds = %sw.bb11691
+  br label %end_opcode
+
+sw.bb30351:                                       ; preds = %end_opcode
+  br label %sw.default42406
+
+sw.default42406:                                  ; preds = %sw.bb30351
+  br label %end_opcode
+
+indirectgoto:                                     ; preds = %run_opcode, %while.body
+  %opcode.0 = phi i8 [ undef, %while.body ], [ %tmp276, %run_opcode ] ; <i8> [#uses=2]
+  indirectbr i8* undef, [label %run_opcode, label %if.else295, label %end_opcode]
+}

test/Transforms/LoopSimplify/indirectbr.ll

@@ -81,3 +81,20 @@ L1:
   %y = phi i64 [ %z, %L0 ], [ 1, %entry ]
   ret i64 %y
 }
+
+define void @pr5502() nounwind {
+entry:
+  br label %while.cond
+
+while.cond:
+  br i1 undef, label %while.body, label %while.end
+
+while.body:
+  indirectbr i8* undef, [label %end_opcode, label %end_opcode]
+
+end_opcode:
+  br i1 false, label %end_opcode, label %while.cond
+
+while.end:
+  ret void
+}