[LCSSA] Perform LCSSA verification only for the current loop nest.

Now LPPassManager will run LCSSA verification only for the top-level loop
which was processed on the current iteration.

Differential Revision: https://reviews.llvm.org/D25873

llvm-svn: 285394

2 files changed, 30 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index 5d818cc734b..68c6b74d5e5 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -51,6 +51,15 @@ using namespace llvm;
 
 STATISTIC(NumLCSSA, "Number of live out of a loop variables");
 
+#ifdef EXPENSIVE_CHECKS
+static bool VerifyLoopLCSSA = true;
+#else
+static bool VerifyLoopLCSSA = false;
+#endif
+static cl::opt<bool,true>
+VerifyLoopLCSSAFlag("verify-loop-lcssa", cl::location(VerifyLoopLCSSA),
+                    cl::desc("Verify loop lcssa form (time consuming)"));
+
 /// Return true if the specified block is in the list.
 static bool isExitBlock(BasicBlock *BB,
                         const SmallVectorImpl<BasicBlock *> &ExitBlocks) {
@@ -322,10 +331,17 @@ struct LCSSAWrapperPass : public FunctionPass {
 
   bool runOnFunction(Function &F) override;
   void verifyAnalysis() const override {
-    assert(
-        all_of(*LI,
-               [&](Loop *L) { return L->isRecursivelyLCSSAForm(*DT, *LI); }) &&
-        "LCSSA form is broken!");
+    // This check is very expensive. On the loop intensive compiles it may cause
+    // up to 10x slowdown. Currently it's disabled by default. LPPassManager
+    // always does limited form of the LCSSA verification. Similar reasoning
+    // was used for the LoopInfo verifier.
+    if (VerifyLoopLCSSA) {
+      assert(all_of(*LI,
+                    [&](Loop *L) {
+                      return L->isRecursivelyLCSSAForm(*DT, *LI);
+                    }) &&
+             "LCSSA form is broken!");
+    }
   };
 
   /// This transformation requires natural loop information & requires that
@@ -342,6 +358,10 @@ struct LCSSAWrapperPass : public FunctionPass {
     AU.addPreserved<GlobalsAAWrapperPass>();
     AU.addPreserved<ScalarEvolutionWrapperPass>();
     AU.addPreserved<SCEVAAWrapperPass>();
+
+    // This is needed to perform LCSSA verification inside LPPassManager
+    AU.addRequired<LCSSAVerificationPass>();
+    AU.addPreserved<LCSSAVerificationPass>();
   }
 };
 }
@@ -351,6 +371,7 @@ INITIALIZE_PASS_BEGIN(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
                       false, false)
 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LCSSAVerificationPass)
 INITIALIZE_PASS_END(LCSSAWrapperPass, "lcssa", "Loop-Closed SSA Form Pass",
                     false, false)
 
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 88786899848..824bc141775 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -17,6 +17,7 @@
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
@@ -946,6 +947,10 @@ void llvm::getLoopAnalysisUsage(AnalysisUsage &AU) {
   AU.addPreservedID(LoopSimplifyID);
   AU.addRequiredID(LCSSAID);
   AU.addPreservedID(LCSSAID);
+  // This is used in the LPPassManager to perform LCSSA verification on passes
+  // which preserve lcssa form
+  AU.addRequired<LCSSAVerificationPass>();
+  AU.addPreserved<LCSSAVerificationPass>();
 
   // Loop passes are designed to run inside of a loop pass manager which means
   // that any function analyses they require must be required by the first loop