LSR fix: broaden the check for loop preheaders.

It's becoming clear that LoopSimplify needs to unconditionally create loop preheaders. But that is a bigger fix. For now, continuing to hack LSR.
Fixes rdar://10701050 "Cannot split an edge from an IndirectBrInst" assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148288 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 85f1389fe31934d5a34515672b5b8262000a0323..baf566906b6632627cb51a124cbc5f26c26a5b73 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4518,11 +4518,19 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
   if (!L->isLoopSimplifyForm())
     return;
 
-  // All outer loops must have preheaders, or SCEVExpander may not be able to
-  // materialize an AddRecExpr whose Start is an outer AddRecExpr.
-  for (const Loop *OuterLoop = L; (OuterLoop = OuterLoop->getParentLoop());) {
-    if (!OuterLoop->getLoopPreheader())
-      return;
+  // All dominating loops must have preheaders, or SCEVExpander may not be able
+  // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
+  //
+  // FIXME: This is a little absurd. I think LoopSimplify should be taught
+  // to create a preheader under any circumstance.
+  for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
+       Rung; Rung = Rung->getIDom()) {
+    BasicBlock *BB = Rung->getBlock();
+    const Loop *DomLoop = LI.getLoopFor(BB);
+    if (DomLoop && DomLoop->getHeader() == BB) {
+      if (!DomLoop->getLoopPreheader())
+        return;
+    }
   }
   // If there's no interesting work to be done, bail early.
   if (IU.empty()) return;

diff --git a/test/Transforms/LoopStrengthReduce/2012-01-16-nopreheader.ll b/test/Transforms/LoopStrengthReduce/2012-01-16-nopreheader.ll
new file mode 100644 (file)
index 0000000..3036a7e
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/2012-01-16-nopreheader.ll
@@ -0,0 +1,113 @@
+; RUN: opt -loop-reduce -S < %s | FileCheck %s
+;
+; <rdar://10701050> "Cannot split an edge from an IndirectBrInst" assert.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin10.0.0"
+
+; while.cond197 is a dominates the simplified loop while.cond238 but
+; has no with no preheader.
+;
+; CHECK: @nopreheader
+; CHECK: %while.cond238
+; CHECK: phi i64
+; CHECK-NOT: phi
+; CHECK: indirectbr
+define void @nopreheader(i8* %end) nounwind {
+entry:
+  br label %while.cond179
+
+while.cond179:                                    ; preds = %if.end434, %if.end369, %if.end277, %if.end165
+  %s.1 = phi i8* [ undef, %if.end434 ], [ %incdec.ptr356, %if.end348 ], [ undef, %entry ]
+  indirectbr i8* undef, [label %land.rhs184, label %while.end453]
+
+land.rhs184:                                      ; preds = %while.cond179
+  indirectbr i8* undef, [label %while.end453, label %while.cond197]
+
+while.cond197:                                    ; preds = %land.rhs202, %land.rhs184
+  %0 = phi i64 [ %indvar.next11, %land.rhs202 ], [ 0, %land.rhs184 ]
+  indirectbr i8* undef, [label %land.rhs202, label %while.end215]
+
+land.rhs202:                                      ; preds = %while.cond197
+  %indvar.next11 = add i64 %0, 1
+  indirectbr i8* undef, [label %while.end215, label %while.cond197]
+
+while.end215:                                     ; preds = %land.rhs202, %while.cond197
+  indirectbr i8* undef, [label %PREMATURE, label %if.end221]
+
+if.end221:                                        ; preds = %while.end215
+  indirectbr i8* undef, [label %while.cond238.preheader, label %lor.lhs.false227]
+
+lor.lhs.false227:                                 ; preds = %if.end221
+  indirectbr i8* undef, [label %while.cond238.preheader, label %if.else]
+
+while.cond238.preheader:                          ; preds = %lor.lhs.false227, %if.end221
+  %tmp16 = add i64 %0, 2
+  indirectbr i8* undef, [label %while.cond238]
+
+while.cond238:                                    ; preds = %land.rhs243, %while.cond238.preheader
+  %1 = phi i64 [ %indvar.next15, %land.rhs243 ], [ 0, %while.cond238.preheader ]
+  %tmp36 = add i64 %tmp16, %1
+  %s.3 = getelementptr i8* %s.1, i64 %tmp36
+  %cmp241 = icmp ult i8* %s.3, %end
+  indirectbr i8* undef, [label %land.rhs243, label %while.end256]
+
+land.rhs243:                                      ; preds = %while.cond238
+  %indvar.next15 = add i64 %1, 1
+  indirectbr i8* undef, [label %while.end256, label %while.cond238]
+
+while.end256:                                     ; preds = %land.rhs243, %while.cond238
+  indirectbr i8* undef, [label %PREMATURE]
+
+if.else:                                          ; preds = %lor.lhs.false227
+  indirectbr i8* undef, [label %if.then297, label %if.else386]
+
+if.then297:                                       ; preds = %if.else
+  indirectbr i8* undef, [label %PREMATURE, label %if.end307]
+
+if.end307:                                        ; preds = %if.then297
+  indirectbr i8* undef, [label %if.end314, label %FAIL]
+
+if.end314:                                        ; preds = %if.end307
+  indirectbr i8* undef, [label %if.end340]
+
+if.end340:                                        ; preds = %while.end334
+  indirectbr i8* undef, [label %PREMATURE, label %if.end348]
+
+if.end348:                                        ; preds = %if.end340
+  %incdec.ptr356 = getelementptr inbounds i8* undef, i64 2
+  indirectbr i8* undef, [label %while.cond179]
+
+if.else386:                                       ; preds = %if.else
+  indirectbr i8* undef, [label %while.end453, label %if.end434]
+
+if.end434:                                        ; preds = %if.then428, %if.end421
+  indirectbr i8* undef, [label %while.cond179]
+
+while.end453:                                     ; preds = %if.else386, %land.rhs184, %while.cond179
+  indirectbr i8* undef, [label %PREMATURE, label %if.end459]
+
+if.end459:                                        ; preds = %while.end453
+  indirectbr i8* undef, [label %if.then465, label %FAIL]
+
+if.then465:                                       ; preds = %if.end459
+  indirectbr i8* undef, [label %return, label %if.then479]
+
+if.then479:                                       ; preds = %if.then465
+  indirectbr i8* undef, [label %return]
+
+FAIL:                                             ; preds = %if.end459, %if.end307, %land.lhs.true142, %land.lhs.true131, %while.end
+  indirectbr i8* undef, [label %DECL_FAIL]
+
+PREMATURE:                                        ; preds = %while.end453, %while.end415, %if.end340, %while.end334, %if.then297, %while.end256, %while.end215
+  indirectbr i8* undef, [label %return, label %if.then495]
+
+if.then495:                                       ; preds = %PREMATURE
+  indirectbr i8* undef, [label %return]
+
+DECL_FAIL:                                        ; preds = %if.then488, %FAIL, %land.lhs.true99, %lor.lhs.false, %if.end83, %if.then39, %if.end
+  indirectbr i8* undef, [label %return]
+
+return:                                           ; preds = %if.then512, %if.end504, %DECL_FAIL, %if.then495, %PREMATURE, %if.then479, %if.then465, %if.then69, %if.end52, %if.end19, %if.then
+  ret void
+}