[CodeExtractor] Allow extracting blocks with exception handling

This is a CodeExtractor improvement which adds support for extracting blocks
which have exception handling constructs if that is legal to do. CodeExtractor
performs validation checks to ensure that extraction is legal when it finds
invoke instructions or EH pads (landingpad, catchswitch, or cleanuppad) in
blocks to be extracted.

I have also added an option to allow extraction of blocks with alloca
instructions, but no validation is done for allocas. CodeExtractor caller has
to validate it himself before allowing alloca instructions to be extracted.
By default allocas are still not allowed in extraction blocks.

Differential Revision: https://reviews.llvm.org/D45904

llvm-svn: 332151

llvm/include/llvm/Transforms/Utils/CodeExtractor.h

@@ -72,11 +72,13 @@ class Value;
     /// sequence out into its new function. When a DominatorTree is also given,
     /// extra checking and transformations are enabled. If AllowVarArgs is true,
     /// vararg functions can be extracted. This is safe, if all vararg handling
-    /// code is extracted, including vastart.
+    /// code is extracted, including vastart. If AllowAlloca is true, then
+    /// extraction of blocks containing alloca instructions would be possible,
+    /// however code extractor won't validate whether extraction is legal. 
     CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT = nullptr,
                   bool AggregateArgs = false, BlockFrequencyInfo *BFI = nullptr,
                   BranchProbabilityInfo *BPI = nullptr,
-                  bool AllowVarArgs = false);
+                  bool AllowVarArgs = false, bool AllowAlloca = false);
 
     /// Create a code extractor for a loop body.
     ///
@@ -86,14 +88,6 @@ class Value;
                   BlockFrequencyInfo *BFI = nullptr,
                   BranchProbabilityInfo *BPI = nullptr);
 
-    /// Check to see if a block is valid for extraction.
-    ///
-    /// Blocks containing EHPads, allocas and invokes are not valid. If
-    /// AllowVarArgs is true, blocks with vastart can be extracted. This is
-    /// safe, if all vararg handling code is extracted, including vastart.
-    static bool isBlockValidForExtraction(const BasicBlock &BB,
-                                          bool AllowVarArgs);
-
     /// Perform the extraction, returning the new function.
     ///
     /// Returns zero when called on a CodeExtractor instance where isEligible

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -79,11 +79,9 @@ AggregateArgsOpt("aggregate-extracted-args", cl::Hidden,
                  cl::desc("Aggregate arguments to code-extracted functions"));
 
 /// Test whether a block is valid for extraction.
-bool CodeExtractor::isBlockValidForExtraction(const BasicBlock &BB,
-                                              bool AllowVarArgs) {
-  // Landing pads must be in the function where they were inserted for cleanup.
-  if (BB.isEHPad())
-    return false;
+static bool isBlockValidForExtraction(const BasicBlock &BB,
+                                      const SetVector<BasicBlock *> &Result,
+                                      bool AllowVarArgs, bool AllowAlloca) {
   // taking the address of a basic block moved to another function is illegal
   if (BB.hasAddressTaken())
     return false;
@@ -112,11 +110,63 @@ bool CodeExtractor::isBlockValidForExtraction(const BasicBlock &BB,
     }
   }
 
-  // Don't hoist code containing allocas or invokes. If explicitly requested,
-  // allow vastart.
+  // If explicitly requested, allow vastart and alloca. For invoke instructions
+  // verify that extraction is valid.
   for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
-    if (isa<AllocaInst>(I) || isa<InvokeInst>(I))
-      return false;
+    if (isa<AllocaInst>(I)) {
+       if (!AllowAlloca)
+         return false;
+       continue;
+    }
+
+    if (const auto *II = dyn_cast<InvokeInst>(I)) {
+      // Unwind destination (either a landingpad, catchswitch, or cleanuppad)
+      // must be a part of the subgraph which is being extracted.
+      if (auto *UBB = II->getUnwindDest())
+        if (!Result.count(UBB))
+          return false;
+      continue;
+    }
+
+    // All catch handlers of a catchswitch instruction as well as the unwind
+    // destination must be in the subgraph.
+    if (const auto *CSI = dyn_cast<CatchSwitchInst>(I)) {
+      if (auto *UBB = CSI->getUnwindDest())
+        if (!Result.count(UBB))
+          return false;
+      for (auto *HBB : CSI->handlers())
+        if (!Result.count(const_cast<BasicBlock*>(HBB)))
+          return false;
+      continue;
+    }
+
+    // Make sure that entire catch handler is within subgraph. It is sufficient
+    // to check that catch return's block is in the list.
+    if (const auto *CPI = dyn_cast<CatchPadInst>(I)) {
+      for (const auto *U : CPI->users())
+        if (const auto *CRI = dyn_cast<CatchReturnInst>(U))
+          if (!Result.count(const_cast<BasicBlock*>(CRI->getParent())))
+            return false;
+      continue;
+    }
+
+    // And do similar checks for cleanup handler - the entire handler must be
+    // in subgraph which is going to be extracted. For cleanup return should
+    // additionally check that the unwind destination is also in the subgraph.
+    if (const auto *CPI = dyn_cast<CleanupPadInst>(I)) {
+      for (const auto *U : CPI->users())
+        if (const auto *CRI = dyn_cast<CleanupReturnInst>(U))
+          if (!Result.count(const_cast<BasicBlock*>(CRI->getParent())))
+            return false;
+      continue;
+    }
+    if (const auto *CRI = dyn_cast<CleanupReturnInst>(I)) {
+      if (auto *UBB = CRI->getUnwindDest())
+        if (!Result.count(UBB))
+          return false;
+      continue;
+    }
+
     if (const CallInst *CI = dyn_cast<CallInst>(I))
       if (const Function *F = CI->getCalledFunction())
         if (F->getIntrinsicID() == Intrinsic::vastart) {
@@ -133,7 +183,7 @@ bool CodeExtractor::isBlockValidForExtraction(const BasicBlock &BB,
 /// Build a set of blocks to extract if the input blocks are viable.
 static SetVector<BasicBlock *>
 buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
-                        bool AllowVarArgs) {
+                        bool AllowVarArgs, bool AllowAlloca) {
   assert(!BBs.empty() && "The set of blocks to extract must be non-empty");
   SetVector<BasicBlock *> Result;
 
@@ -146,32 +196,41 @@ buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
 
     if (!Result.insert(BB))
       llvm_unreachable("Repeated basic blocks in extraction input");
-    if (!CodeExtractor::isBlockValidForExtraction(*BB, AllowVarArgs)) {
-      Result.clear();
-      return Result;
-    }
   }
 
-#ifndef NDEBUG
-  for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()),
-                                         E = Result.end();
-       I != E; ++I)
-    for (pred_iterator PI = pred_begin(*I), PE = pred_end(*I);
-         PI != PE; ++PI)
-      assert(Result.count(*PI) &&
-             "No blocks in this region may have entries from outside the region"
-             " except for the first block!");
-#endif
+  for (auto *BB : Result) {
+    if (!isBlockValidForExtraction(*BB, Result, AllowVarArgs, AllowAlloca))
+      return {};
+
+    // Make sure that the first block is not a landing pad.
+    if (BB == Result.front()) {
+      if (BB->isEHPad()) {
+        DEBUG(dbgs() << "The first block cannot be an unwind block\n");
+        return {};
+      }
+      continue;
+    }
+
+    // All blocks other than the first must not have predecessors outside of
+    // the subgraph which is being extracted.
+    for (auto *PBB : predecessors(BB))
+      if (!Result.count(PBB)) {
+        DEBUG(dbgs() << "No blocks in this region may have entries from "
+                         "outside the region except for the first block!\n");
+        return {};
+      }
+  }
 
   return Result;
 }
 
 CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT,
                              bool AggregateArgs, BlockFrequencyInfo *BFI,
-                             BranchProbabilityInfo *BPI, bool AllowVarArgs)
+                             BranchProbabilityInfo *BPI, bool AllowVarArgs,
+                             bool AllowAlloca)
     : DT(DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
       BPI(BPI), AllowVarArgs(AllowVarArgs),
-      Blocks(buildExtractionBlockSet(BBs, DT, AllowVarArgs)) {}
+      Blocks(buildExtractionBlockSet(BBs, DT, AllowVarArgs, AllowAlloca)) {}
 
 CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs,
                              BlockFrequencyInfo *BFI,
@@ -179,7 +238,8 @@ CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs,
     : DT(&DT), AggregateArgs(AggregateArgs || AggregateArgsOpt), BFI(BFI),
       BPI(BPI), AllowVarArgs(false),
       Blocks(buildExtractionBlockSet(L.getBlocks(), &DT,
-                                     /* AllowVarArgs */ false)) {}
+                                     /* AllowVarArgs */ false,
+                                     /* AllowAlloca */ false)) {}
 
 /// definedInRegion - Return true if the specified value is defined in the
 /// extracted region.
@@ -1178,6 +1238,10 @@ Function *CodeExtractor::extractCodeRegion() {
 
   moveCodeToFunction(newFunction);
 
+  // Propagate personality info to the new function if there is one.
+  if (oldFunction->hasPersonalityFn())
+    newFunction->setPersonalityFn(oldFunction->getPersonalityFn());
+
   // Update the branch weights for the exit block.
   if (BFI && NumExitBlocks > 1)
     calculateNewCallTerminatorWeights(codeReplacer, ExitWeights, BPI);

llvm/test/Transforms/CodeExtractor/inline_eh.ll

@@ -0,0 +1,52 @@
+; RUN: opt < %s -skip-partial-inlining-cost-analysis -partial-inliner -S  | FileCheck %s
+; RUN: opt < %s -skip-partial-inlining-cost-analysis -passes=partial-inliner -S  | FileCheck %s
+
+declare void @bar()
+declare i32 @__gxx_personality_v0(...)
+declare i8* @__cxa_begin_catch(i8*)
+declare void @__cxa_end_catch()
+
+define internal void @callee(i1 %cond) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+entry:
+  br i1 %cond, label %if.then, label %if.end
+
+if.then:
+  invoke void @bar()
+          to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+  br label %try.cont
+
+lpad:
+  %0 = landingpad { i8*, i32 }
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = extractvalue { i8*, i32 } %0, 1
+  br label %catch
+
+catch:
+  %3 = call i8* @__cxa_begin_catch(i8* %1)
+  call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+define internal void @caller(i1 %cond) {
+; CHECK-LABEL: define {{.*}} @caller
+entry:
+; CHECK: entry:
+; CHECK-NEXT: br i1
+; CHECK: codeRepl.i:
+; CHECK-NEXT: call void @callee.1_{{.*}}()
+  call void @callee(i1 %cond)
+  ret void
+}
+
+; CHECK-LABEL: define {{.*}} @callee.1_{{.*}}() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+; CHECK: invoke void @bar()
+; CHECK: landingpad

llvm/test/Transforms/CodeExtractor/inline_eh_1.ll

@@ -0,0 +1,56 @@
+; RUN: opt < %s -skip-partial-inlining-cost-analysis -partial-inliner -S  | FileCheck %s
+; RUN: opt < %s -skip-partial-inlining-cost-analysis -passes=partial-inliner -S  | FileCheck %s
+
+declare dso_local void @bar()
+declare dso_local i32 @__CxxFrameHandler3(...)
+
+define internal void @callee(i1 %cond) personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  br i1 %cond, label %if.then, label %if.end
+
+if.then:
+  invoke void @bar()
+          to label %invoke.cont unwind label %ehcleanup
+
+invoke.cont:
+  br label %try.cont
+
+ehcleanup:
+  %0 = cleanuppad within none []
+  cleanupret from %0 unwind label %catch.dispatch
+
+catch.dispatch:
+  %1 = catchswitch within none [label %catch] unwind to caller
+
+catch:
+  %2 = catchpad within %1 [i8* null, i32 64, i8* null]
+  catchret from %2 to label %catchret.dest
+
+catchret.dest:
+  br label %try.cont
+
+try.cont:
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+define internal void @caller(i1 %cond) {
+; CHECK-LABEL: define {{.*}} @caller
+entry:
+; CHECK: entry:
+; CHECK-NEXT: br i1
+; CHECK: codeRepl.i:
+; CHECK-NEXT: call void @callee.1_{{.*}}()
+  call void @callee(i1 %cond)
+  ret void
+}
+
+; CHECK-LABEL: define {{.*}} @callee.1_{{.*}}() personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*)
+; CHECK: invoke void @bar()
+; CHECK: cleanuppad
+; CHECK-NEXT: cleanupret
+; CHECK: catchswitch
+; CHECK: catchpad
+; CHECK-NEXT: catchret