Fix SCEV cache invalidation in LCSSA and LoopSimplify.

The LoopSimplify bug is pretty harmless because the loop goes from unanalyzable
to analyzable but the LCSSA bug is very nasty. It only comes into play with a
specific order of the LoopPassManager worklist and can cause actual
miscompilations, when a SCEV refers to a value that has been replaced with PHI
node. SCEVExpander may then insert code into the wrong place, either violating
domination or randomly miscompiling stuff.

Comes with an extensive test case reduced from the test-suite with
bugpoint+SCEVValidator.

llvm-svn: 166787

diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index b654111..833dea5 100644 (file)
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -53,6 +53,8 @@ namespace {
 
     // Cached analysis information for the current function.
     DominatorTree *DT;
+    LoopInfo *LI;
+    ScalarEvolution *SE;
     std::vector<BasicBlock*> LoopBlocks;
     PredIteratorCache PredCache;
     Loop *L;
@@ -117,6 +119,8 @@ bool LCSSA::runOnLoop(Loop *TheLoop, LPPassManager &LPM) {
   L = TheLoop;
   
   DT = &getAnalysis<DominatorTree>();
+  LI = &getAnalysis<LoopInfo>();
+  SE = getAnalysisIfAvailable<ScalarEvolution>();
 
   // Get the set of exiting blocks.
   SmallVector<BasicBlock*, 8> ExitBlocks;
@@ -244,6 +248,12 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
     
     // Remember that this phi makes the value alive in this block.
     SSAUpdate.AddAvailableValue(ExitBB, PN);
+
+    // If the exiting block is part of a loop inserting a PHI may change its
+    // SCEV analysis. Conservatively drop any caches from it.
+    if (SE)
+      if (Loop *L = LI->getLoopFor(ExitBB))
+        SE->forgetLoop(L);
   }
   
   // Rewrite all uses outside the loop in terms of the new PHIs we just
@@ -258,6 +268,10 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
     if (PHINode *PN = dyn_cast<PHINode>(User))
       UserBB = PN->getIncomingBlock(*UsesToRewrite[i]);
 
+    // Tell SCEV to reanalyze the value that's about to change.
+    if (SE)
+      SE->forgetValue(*UsesToRewrite[i]);
+
     if (isa<PHINode>(UserBB->begin()) &&
         isExitBlock(UserBB, ExitBlocks)) {
       UsesToRewrite[i]->set(UserBB->begin());

diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 0bc185d..8fce2ac 100644 (file)
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -194,6 +194,11 @@ ReprocessLoop:
 
           BI->setCondition(ConstantInt::get(Cond->getType(),
                                             !L->contains(BI->getSuccessor(0))));
+
+          // This may make the loop analyzable, force SCEV recomputation.
+          if (SE)
+            SE->forgetLoop(L);
+
           Changed = true;
         }
       }

diff --git a/llvm/test/Transforms/IndVarSimplify/verify-scev.ll b/llvm/test/Transforms/IndVarSimplify/verify-scev.ll
new file mode 100644 (file)
index 0000000..019f583
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/verify-scev.ll
@@ -0,0 +1,421 @@
+; RUN: opt < %s -S -indvars -verify-scev
+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-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+define void @test1() nounwind uwtable ssp {
+entry:
+  br i1 undef, label %for.end, label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 false, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  br i1 undef, label %for.end11, label %for.body3
+
+for.body3:                                        ; preds = %for.end
+  unreachable
+
+for.end11:                                        ; preds = %for.end
+  br i1 undef, label %while.body, label %while.end
+
+while.body:                                       ; preds = %for.end11
+  unreachable
+
+while.end:                                        ; preds = %for.end11
+  br i1 undef, label %if.end115, label %for.cond109
+
+for.cond109:                                      ; preds = %while.end
+  unreachable
+
+if.end115:                                        ; preds = %while.end
+  br i1 undef, label %while.body119.lr.ph.lr.ph, label %for.cond612
+
+while.body119.lr.ph.lr.ph:                        ; preds = %if.end115
+  br i1 undef, label %for.cond612, label %if.end123.us
+
+if.end123.us:                                     ; preds = %while.body119.lr.ph.lr.ph
+  br label %for.cond132.us
+
+for.cond132.us:                                   ; preds = %for.cond132.us, %if.end123.us
+  br i1 undef, label %if.then136.us, label %for.cond132.us
+
+if.then136.us:                                    ; preds = %for.cond132.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.body211:                                    ; preds = %while.body211, %if.then136.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.end220:                                     ; preds = %while.body211, %if.then136.us
+  br label %for.cond246.outer
+
+for.cond246.outer:                                ; preds = %for.inc558, %for.cond394.preheader, %if.then274, %for.cond404.preheader, %while.end220
+  br label %for.cond246
+
+for.cond246:                                      ; preds = %for.cond372.loopexit, %for.cond246.outer
+  br i1 undef, label %for.end562, label %if.end250
+
+if.end250:                                        ; preds = %for.cond246
+  br i1 undef, label %if.end256, label %for.end562
+
+if.end256:                                        ; preds = %if.end250
+  %cmp272 = icmp eq i32 undef, undef
+  br i1 %cmp272, label %if.then274, label %for.cond404.preheader
+
+for.cond404.preheader:                            ; preds = %if.end256
+  br i1 undef, label %for.cond246.outer, label %for.body409.lr.ph
+
+for.body409.lr.ph:                                ; preds = %for.cond404.preheader
+  br label %for.body409
+
+if.then274:                                       ; preds = %if.end256
+  br i1 undef, label %for.cond246.outer, label %if.end309
+
+if.end309:                                        ; preds = %if.then274
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.body361:                                      ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.cond372.loopexit:                             ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond394.preheader, label %for.cond246
+
+for.cond394.preheader:                            ; preds = %for.cond372.loopexit
+  br i1 undef, label %for.cond246.outer, label %for.body397
+
+for.body397:                                      ; preds = %for.cond394.preheader
+  unreachable
+
+for.body409:                                      ; preds = %for.inc558, %for.body409.lr.ph
+  %k.029 = phi i32 [ 1, %for.body409.lr.ph ], [ %inc559, %for.inc558 ]
+  br i1 undef, label %if.then412, label %if.else433
+
+if.then412:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.else433:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.end440:                                        ; preds = %if.else433, %if.then412
+  br i1 undef, label %for.inc558, label %if.end461
+
+if.end461:                                        ; preds = %if.end440
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.body517:                                      ; preds = %for.body517, %if.end461
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.cond528.loopexit:                             ; preds = %for.body517, %if.end461
+  br label %for.inc558
+
+for.inc558:                                       ; preds = %for.cond528.loopexit, %if.end440
+  %inc559 = add nsw i32 %k.029, 1
+  %cmp407 = icmp sgt i32 %inc559, undef
+  br i1 %cmp407, label %for.cond246.outer, label %for.body409
+
+for.end562:                                       ; preds = %if.end250, %for.cond246
+  unreachable
+
+for.cond612:                                      ; preds = %while.body119.lr.ph.lr.ph, %if.end115
+  unreachable
+}
+
+define void @test2() nounwind uwtable ssp {
+entry:
+  br i1 undef, label %for.end, label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 undef, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  br i1 undef, label %for.end11, label %for.body3
+
+for.body3:                                        ; preds = %for.end
+  unreachable
+
+for.end11:                                        ; preds = %for.end
+  br i1 undef, label %while.body, label %while.end
+
+while.body:                                       ; preds = %for.end11
+  unreachable
+
+while.end:                                        ; preds = %for.end11
+  br i1 undef, label %if.end115, label %for.cond109
+
+for.cond109:                                      ; preds = %while.end
+  unreachable
+
+if.end115:                                        ; preds = %while.end
+  br i1 undef, label %while.body119.lr.ph.lr.ph, label %for.cond612
+
+while.body119.lr.ph.lr.ph:                        ; preds = %if.end115
+  br i1 undef, label %for.cond612, label %if.end123.us
+
+if.end123.us:                                     ; preds = %while.body119.lr.ph.lr.ph
+  br label %for.cond132.us
+
+for.cond132.us:                                   ; preds = %for.cond132.us, %if.end123.us
+  br i1 undef, label %if.then136.us, label %for.cond132.us
+
+if.then136.us:                                    ; preds = %for.cond132.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.body211:                                    ; preds = %while.body211, %if.then136.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.end220:                                     ; preds = %while.body211, %if.then136.us
+  br label %for.cond246.outer
+
+for.cond246.outer:                                ; preds = %for.inc558, %for.cond394.preheader, %if.then274, %for.cond404.preheader, %while.end220
+  br label %for.cond246
+
+for.cond246:                                      ; preds = %for.cond372.loopexit, %for.cond246.outer
+  br i1 undef, label %for.end562, label %if.end250
+
+if.end250:                                        ; preds = %for.cond246
+  br i1 undef, label %if.end256, label %for.end562
+
+if.end256:                                        ; preds = %if.end250
+  %0 = load i32* undef, align 4
+  br i1 undef, label %if.then274, label %for.cond404.preheader
+
+for.cond404.preheader:                            ; preds = %if.end256
+  %add406 = add i32 0, %0
+  br i1 undef, label %for.cond246.outer, label %for.body409.lr.ph
+
+for.body409.lr.ph:                                ; preds = %for.cond404.preheader
+  br label %for.body409
+
+if.then274:                                       ; preds = %if.end256
+  br i1 undef, label %for.cond246.outer, label %if.end309
+
+if.end309:                                        ; preds = %if.then274
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.body361:                                      ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.cond372.loopexit:                             ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond394.preheader, label %for.cond246
+
+for.cond394.preheader:                            ; preds = %for.cond372.loopexit
+  br i1 undef, label %for.cond246.outer, label %for.body397
+
+for.body397:                                      ; preds = %for.cond394.preheader
+  unreachable
+
+for.body409:                                      ; preds = %for.inc558, %for.body409.lr.ph
+  %k.029 = phi i32 [ 1, %for.body409.lr.ph ], [ %inc559, %for.inc558 ]
+  br i1 undef, label %if.then412, label %if.else433
+
+if.then412:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.else433:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.end440:                                        ; preds = %if.else433, %if.then412
+  br i1 undef, label %for.inc558, label %if.end461
+
+if.end461:                                        ; preds = %if.end440
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.body517:                                      ; preds = %for.body517, %if.end461
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.cond528.loopexit:                             ; preds = %for.body517, %if.end461
+  br label %for.inc558
+
+for.inc558:                                       ; preds = %for.cond528.loopexit, %if.end440
+  %inc559 = add nsw i32 %k.029, 1
+  %cmp407 = icmp sgt i32 %inc559, %add406
+  br i1 %cmp407, label %for.cond246.outer, label %for.body409
+
+for.end562:                                       ; preds = %if.end250, %for.cond246
+  unreachable
+
+for.cond612:                                      ; preds = %while.body119.lr.ph.lr.ph, %if.end115
+  unreachable
+}
+
+define void @test3() nounwind uwtable ssp {
+entry:
+  br i1 undef, label %for.end, label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  br i1 undef, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  br i1 undef, label %for.end11, label %for.body3
+
+for.body3:                                        ; preds = %for.end
+  unreachable
+
+for.end11:                                        ; preds = %for.end
+  br i1 undef, label %while.body, label %while.end
+
+while.body:                                       ; preds = %for.end11
+  unreachable
+
+while.end:                                        ; preds = %for.end11
+  br i1 undef, label %if.end115, label %for.cond109
+
+for.cond109:                                      ; preds = %while.end
+  unreachable
+
+if.end115:                                        ; preds = %while.end
+  br i1 undef, label %while.body119.lr.ph.lr.ph, label %for.cond612
+
+while.body119.lr.ph.lr.ph:                        ; preds = %if.end115
+  br i1 undef, label %for.cond612, label %if.end123.us
+
+if.end123.us:                                     ; preds = %while.body119.lr.ph.lr.ph
+  br label %for.cond132.us
+
+for.cond132.us:                                   ; preds = %for.cond132.us, %if.end123.us
+  br i1 undef, label %if.then136.us, label %for.cond132.us
+
+if.then136.us:                                    ; preds = %for.cond132.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.body211:                                    ; preds = %while.body211, %if.then136.us
+  br i1 undef, label %while.end220, label %while.body211
+
+while.end220:                                     ; preds = %while.body211, %if.then136.us
+  br label %for.cond246.outer
+
+for.cond246.outer:                                ; preds = %for.inc558, %for.cond394.preheader, %if.then274, %for.cond404.preheader, %while.end220
+  br label %for.cond246
+
+for.cond246:                                      ; preds = %for.cond372.loopexit, %for.cond246.outer
+  br i1 undef, label %for.end562, label %if.end250
+
+if.end250:                                        ; preds = %for.cond246
+  br i1 undef, label %if.end256, label %for.end562
+
+if.end256:                                        ; preds = %if.end250
+  br i1 undef, label %if.then274, label %for.cond404.preheader
+
+for.cond404.preheader:                            ; preds = %if.end256
+  br i1 undef, label %for.cond246.outer, label %for.body409.lr.ph
+
+for.body409.lr.ph:                                ; preds = %for.cond404.preheader
+  br label %for.body409
+
+if.then274:                                       ; preds = %if.end256
+  br i1 undef, label %for.cond246.outer, label %if.end309
+
+if.end309:                                        ; preds = %if.then274
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.body361:                                      ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond372.loopexit, label %for.body361
+
+for.cond372.loopexit:                             ; preds = %for.body361, %if.end309
+  br i1 undef, label %for.cond394.preheader, label %for.cond246
+
+for.cond394.preheader:                            ; preds = %for.cond372.loopexit
+  br i1 undef, label %for.cond246.outer, label %for.body397
+
+for.body397:                                      ; preds = %for.cond394.preheader
+  unreachable
+
+for.body409:                                      ; preds = %for.inc558, %for.body409.lr.ph
+  br i1 undef, label %if.then412, label %if.else433
+
+if.then412:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.else433:                                       ; preds = %for.body409
+  br label %if.end440
+
+if.end440:                                        ; preds = %if.else433, %if.then412
+  br i1 undef, label %for.inc558, label %if.end461
+
+if.end461:                                        ; preds = %if.end440
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.body517:                                      ; preds = %for.body517, %if.end461
+  br i1 undef, label %for.cond528.loopexit, label %for.body517
+
+for.cond528.loopexit:                             ; preds = %for.body517, %if.end461
+  br label %for.inc558
+
+for.inc558:                                       ; preds = %for.cond528.loopexit, %if.end440
+  br i1 undef, label %for.cond246.outer, label %for.body409
+
+for.end562:                                       ; preds = %if.end250, %for.cond246
+  unreachable
+
+for.cond612:                                      ; preds = %while.body119.lr.ph.lr.ph, %if.end115
+  unreachable
+}
+
+define void @test4() nounwind uwtable ssp {
+entry:
+  br i1 undef, label %if.end8, label %if.else
+
+if.else:                                          ; preds = %entry
+  br label %if.end8
+
+if.end8:                                          ; preds = %if.else, %entry
+  br i1 undef, label %if.end26, label %if.else22
+
+if.else22:                                        ; preds = %if.end8
+  br label %if.end26
+
+if.end26:                                         ; preds = %if.else22, %if.end8
+  br i1 undef, label %if.end35, label %if.else31
+
+if.else31:                                        ; preds = %if.end26
+  br label %if.end35
+
+if.end35:                                         ; preds = %if.else31, %if.end26
+  br i1 undef, label %for.end226, label %for.body.lr.ph
+
+for.body.lr.ph:                                   ; preds = %if.end35
+  br label %for.body48
+
+for.body48:                                       ; preds = %for.inc221, %for.body.lr.ph
+  br i1 undef, label %for.inc221, label %for.body65.lr.ph
+
+for.body65.lr.ph:                                 ; preds = %for.body48
+  %0 = load i32* undef, align 4
+  br label %for.body65.us
+
+for.body65.us:                                    ; preds = %for.inc219.us, %for.body65.lr.ph
+  %k.09.us = phi i32 [ %inc.us, %for.inc219.us ], [ 1, %for.body65.lr.ph ]
+  %idxprom66.us = sext i32 %k.09.us to i64
+  br i1 undef, label %for.inc219.us, label %if.end72.us
+
+if.end72.us:                                      ; preds = %for.body65.us
+  br i1 undef, label %if.end93.us, label %if.then76.us
+
+if.then76.us:                                     ; preds = %if.end72.us
+  br label %if.end93.us
+
+if.end93.us:                                      ; preds = %if.then76.us, %if.end72.us
+  br i1 undef, label %if.end110.us, label %for.inc219.us
+
+if.end110.us:                                     ; preds = %if.end93.us
+  br i1 undef, label %for.inc219.us, label %for.body142.us
+
+for.body142.us:                                   ; preds = %for.cond139.loopexit.us, %if.end110.us
+  br label %for.cond152.us
+
+for.cond152.us:                                   ; preds = %for.cond152.us, %for.body142.us
+  br i1 undef, label %for.cond139.loopexit.us, label %for.cond152.us
+
+for.inc219.us:                                    ; preds = %for.cond139.loopexit.us, %if.end110.us, %if.end93.us, %for.body65.us
+  %inc.us = add nsw i32 %k.09.us, 1
+  %cmp64.us = icmp sgt i32 %inc.us, %0
+  br i1 %cmp64.us, label %for.inc221, label %for.body65.us
+
+for.cond139.loopexit.us:                          ; preds = %for.cond152.us
+  br i1 undef, label %for.inc219.us, label %for.body142.us
+
+for.inc221:                                       ; preds = %for.inc219.us, %for.body48
+  br label %for.body48
+
+for.end226:                                       ; preds = %if.end35
+  ret void
+}