[SimplifyCFG] don't sink common insts too soon (PR34603)

This should solve:
https://bugs.llvm.org/show_bug.cgi?id=34603
...by preventing SimplifyCFG from altering redundant instructions before early-cse has a chance to run.
It changes the default (canonical-forming) behavior of SimplifyCFG, so we're only doing the
sinking transform later in the optimization pipeline.

Differential Revision: https://reviews.llvm.org/D38566


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320749 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 12 insertions, 3 deletions

diff --git a/include/llvm/Transforms/Scalar.h b/include/llvm/Transforms/Scalar.h
index 07d3d7fc8f6..6fe35b441b5 100644
--- a/include/llvm/Transforms/Scalar.h
+++ b/include/llvm/Transforms/Scalar.h
@@ -267,7 +267,7 @@ FunctionPass *createJumpThreadingPass(int Threshold = -1);
 //
 FunctionPass *createCFGSimplificationPass(
     unsigned Threshold = 1, bool ForwardSwitchCond = false,
-    bool ConvertSwitch = false, bool KeepLoops = true,
+    bool ConvertSwitch = false, bool KeepLoops = true, bool SinkCommon = false,
     std::function<bool(const Function &)> Ftor = nullptr);
 
 //===----------------------------------------------------------------------===//
diff --git a/include/llvm/Transforms/Scalar/SimplifyCFG.h b/include/llvm/Transforms/Scalar/SimplifyCFG.h
index ed6b1b1853b..1afb9c7f954 100644
--- a/include/llvm/Transforms/Scalar/SimplifyCFG.h
+++ b/include/llvm/Transforms/Scalar/SimplifyCFG.h
@@ -39,7 +39,8 @@ public:
       : SimplifyCFGPass(SimplifyCFGOptions()
                             .forwardSwitchCondToPhi(false)
                             .convertSwitchToLookupTable(false)
-                            .needCanonicalLoops(true)) {}
+                            .needCanonicalLoops(true)
+                            .sinkCommonInsts(false)) {}
 
 
   /// Construct a pass with optional optimizations.
diff --git a/include/llvm/Transforms/Utils/Local.h b/include/llvm/Transforms/Utils/Local.h
index 6d8d8591fa1..7dd21dfc1a8 100644
--- a/include/llvm/Transforms/Utils/Local.h
+++ b/include/llvm/Transforms/Utils/Local.h
@@ -63,16 +63,20 @@ struct SimplifyCFGOptions {
   bool ForwardSwitchCondToPhi;
   bool ConvertSwitchToLookupTable;
   bool NeedCanonicalLoop;
+  bool SinkCommonInsts;
   AssumptionCache *AC;
 
   SimplifyCFGOptions(unsigned BonusThreshold = 1,
                      bool ForwardSwitchCond = false,
                      bool SwitchToLookup = false, bool CanonicalLoops = true,
+                     bool SinkCommon = false,
                      AssumptionCache *AssumpCache = nullptr)
       : BonusInstThreshold(BonusThreshold),
         ForwardSwitchCondToPhi(ForwardSwitchCond),
         ConvertSwitchToLookupTable(SwitchToLookup),
-        NeedCanonicalLoop(CanonicalLoops), AC(AssumpCache) {}
+        NeedCanonicalLoop(CanonicalLoops),
+        SinkCommonInsts(SinkCommon),
+        AC(AssumpCache) {}
 
   // Support 'builder' pattern to set members by name at construction time.
   SimplifyCFGOptions &bonusInstThreshold(int I) {
@@ -91,6 +95,10 @@ struct SimplifyCFGOptions {
     NeedCanonicalLoop = B;
     return *this;
   }
+  SimplifyCFGOptions &sinkCommonInsts(bool B) {
+    SinkCommonInsts = B;
+    return *this;
+  }
   SimplifyCFGOptions &setAssumptionCache(AssumptionCache *Cache) {
     AC = Cache;
     return *this;