[SimplifyCFG] use pass options and remove the latesimplifycfg pass

This is no-functional-change-intended.

This is repackaging the functionality of D30333 (defer switch-to-lookup-tables) and 
D35411 (defer folding unconditional branches) with pass parameters rather than a named
"latesimplifycfg" pass. Now that we have individual options to control the functionality,
we could decouple when these fire (but that's an independent patch if desired). 

The next planned step would be to add another option bit to disable the sinking transform
mentioned in D38566. This should also make it clear that the new pass manager needs to
be updated to limit simplifycfg in the same way as the old pass manager.

Differential Revision: https://reviews.llvm.org/D38631

llvm-svn: 316835

6 files changed, 38 insertions, 18 deletions

diff --git a/llvm/include/llvm-c/Transforms/Scalar.h b/llvm/include/llvm-c/Transforms/Scalar.h
index b9612b9cec0..8991e090484 100644
--- a/llvm/include/llvm-c/Transforms/Scalar.h
+++ b/llvm/include/llvm-c/Transforms/Scalar.h
@@ -44,9 +44,6 @@ void LLVMAddAlignmentFromAssumptionsPass(LLVMPassManagerRef PM);
 /** See llvm::createCFGSimplificationPass function. */
 void LLVMAddCFGSimplificationPass(LLVMPassManagerRef PM);
 
-/** See llvm::createLateCFGSimplificationPass function. */
-void LLVMAddLateCFGSimplificationPass(LLVMPassManagerRef PM);
-
 /** See llvm::createDeadStoreEliminationPass function. */
 void LLVMAddDeadStoreEliminationPass(LLVMPassManagerRef PM);
 
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 6b0e6acadad..c3ad8fe41af 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -174,7 +174,6 @@ void initializeIntervalPartitionPass(PassRegistry&);
 void initializeJumpThreadingPass(PassRegistry&);
 void initializeLCSSAVerificationPassPass(PassRegistry&);
 void initializeLCSSAWrapperPassPass(PassRegistry&);
-void initializeLateCFGSimplifyPassPass(PassRegistry&);
 void initializeLazyBlockFrequencyInfoPassPass(PassRegistry&);
 void initializeLazyBranchProbabilityInfoPassPass(PassRegistry&);
 void initializeLazyMachineBlockFrequencyInfoPassPass(PassRegistry&);
diff --git a/llvm/include/llvm/LinkAllPasses.h b/llvm/include/llvm/LinkAllPasses.h
index abc3bac9367..765e63926da 100644
--- a/llvm/include/llvm/LinkAllPasses.h
+++ b/llvm/include/llvm/LinkAllPasses.h
@@ -75,7 +75,6 @@ namespace {
       (void) llvm::createCallGraphDOTPrinterPass();
       (void) llvm::createCallGraphViewerPass();
       (void) llvm::createCFGSimplificationPass();
-      (void) llvm::createLateCFGSimplificationPass();
       (void) llvm::createCFLAndersAAWrapperPass();
       (void) llvm::createCFLSteensAAWrapperPass();
       (void) llvm::createStructurizeCFGPass();
diff --git a/llvm/include/llvm/Transforms/Scalar.h b/llvm/include/llvm/Transforms/Scalar.h
index d9a10c086d9..8ef65774a93 100644
--- a/llvm/include/llvm/Transforms/Scalar.h
+++ b/llvm/include/llvm/Transforms/Scalar.h
@@ -255,18 +255,12 @@ FunctionPass *createJumpThreadingPass(int Threshold = -1);
 //===----------------------------------------------------------------------===//
 //
 // CFGSimplification - Merge basic blocks, eliminate unreachable blocks,
-// simplify terminator instructions, etc...
+// simplify terminator instructions, convert switches to lookup tables, etc.
 //
 FunctionPass *createCFGSimplificationPass(
-    int Threshold = -1, std::function<bool(const Function &)> Ftor = nullptr);
-
-//===----------------------------------------------------------------------===//
-//
-// LateCFGSimplification - Like CFGSimplification, but may also
-// convert switches to lookup tables.
-//
-FunctionPass *createLateCFGSimplificationPass(
-    int Threshold = -1, std::function<bool(const Function &)> Ftor = nullptr);
+    unsigned Threshold = 1, bool ForwardSwitchCond = false,
+    bool ConvertSwitch = false, bool KeepLoops = true,
+    std::function<bool(const Function &)> Ftor = nullptr);
 
 //===----------------------------------------------------------------------===//
 //
diff --git a/llvm/include/llvm/Transforms/Scalar/SimplifyCFG.h b/llvm/include/llvm/Transforms/Scalar/SimplifyCFG.h
index ef47fa8e684..e955673283e 100644
--- a/llvm/include/llvm/Transforms/Scalar/SimplifyCFG.h
+++ b/llvm/include/llvm/Transforms/Scalar/SimplifyCFG.h
@@ -31,8 +31,16 @@ class SimplifyCFGPass : public PassInfoMixin<SimplifyCFGPass> {
   SimplifyCFGOptions Options;
 
 public:
-  /// Construct a pass with default options.
-  SimplifyCFGPass();
+  /// The default constructor sets the pass options to create optimal IR,
+  /// rather than canonical IR. That is, by default we do transformations that
+  /// are likely to improve performance but make analysis more difficult.
+  /// FIXME: This is inverted from what most instantiations of the pass should
+  /// be.
+  SimplifyCFGPass()
+      : SimplifyCFGPass(SimplifyCFGOptions()
+                            .forwardSwitchCondToPhi(true)
+                            .convertSwitchToLookupTable(true)
+                            .needCanonicalLoops(false)) {}
 
   /// Construct a pass with optional optimizations.
   SimplifyCFGPass(const SimplifyCFGOptions &PassOptions);
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index fe344a7fac6..8d54ef3436a 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -65,13 +65,36 @@ struct SimplifyCFGOptions {
   bool NeedCanonicalLoop;
   AssumptionCache *AC;
 
-  SimplifyCFGOptions(int BonusThreshold = 1, bool ForwardSwitchCond = false,
+  SimplifyCFGOptions(unsigned BonusThreshold = 1,
+                     bool ForwardSwitchCond = false,
                      bool SwitchToLookup = false, bool CanonicalLoops = true,
                      AssumptionCache *AssumpCache = nullptr)
       : BonusInstThreshold(BonusThreshold),
         ForwardSwitchCondToPhi(ForwardSwitchCond),
         ConvertSwitchToLookupTable(SwitchToLookup),
         NeedCanonicalLoop(CanonicalLoops), AC(AssumpCache) {}
+
+  // Support 'builder' pattern to set members by name at construction time.
+  SimplifyCFGOptions &bonusInstThreshold(int I) {
+    BonusInstThreshold = I;
+    return *this;
+  }
+  SimplifyCFGOptions &forwardSwitchCondToPhi(bool B) {
+    ForwardSwitchCondToPhi = B;
+    return *this;
+  }
+  SimplifyCFGOptions &convertSwitchToLookupTable(bool B) {
+    ConvertSwitchToLookupTable = B;
+    return *this;
+  }
+  SimplifyCFGOptions &needCanonicalLoops(bool B) {
+    NeedCanonicalLoop = B;
+    return *this;
+  }
+  SimplifyCFGOptions &setAssumptionCache(AssumptionCache *Cache) {
+    AC = Cache;
+    return *this;
+  }
 };
 
 //===----------------------------------------------------------------------===//