From 3d90bb79c4e81dfd76afe26a771097dc3852674c Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 3 May 2016 03:57:40 +0000
Subject: [PATCH] [LoopUnroll] Unroll loops which have exit blocks to EH pads

We were overly cautious in our analysis of loops which have invokes
which unwind to EH pads.  The loop unroll transform is safe because it
only clones blocks in the loop body, it does not try to split critical
edges involving EH pads.  Instead, move the necessary safety check to
LoopUnswitch.

N.B. The safety check for loop unswitch is covered by an existing test
which fails without it.

llvm-svn: 268357
---
 llvm/include/llvm/IR/CallSite.h                    |  8 +++++
 llvm/lib/Analysis/LoopInfo.cpp                     | 19 ++--------
 llvm/lib/Transforms/Scalar/LoopUnswitch.cpp        |  5 +++
 .../Transforms/LoopUnroll/unroll-cleanuppad.ll     | 40 ++++++++++++++++++++++
 4 files changed, 56 insertions(+), 16 deletions(-)
 create mode 100644 llvm/test/Transforms/LoopUnroll/unroll-cleanuppad.ll

diff --git a/llvm/include/llvm/IR/CallSite.h b/llvm/include/llvm/IR/CallSite.h
index ad66cfb..1a08434 100644
--- a/llvm/include/llvm/IR/CallSite.h
+++ b/llvm/include/llvm/IR/CallSite.h
@@ -426,6 +426,14 @@ public:
     CALLSITE_DELEGATE_SETTER(setDoesNotThrow());
   }
 
+  /// @brief Determine if the call can be duplicated.
+  bool cannotDuplicate() const {
+    CALLSITE_DELEGATE_GETTER(cannotDuplicate());
+  }
+  void setCannotDuplicate() {
+    CALLSITE_DELEGATE_GETTER(setCannotDuplicate());
+  }
+
   /// @brief Determine if the call is convergent.
   bool isConvergent() const {
     CALLSITE_DELEGATE_GETTER(isConvergent());
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 277bd0d..2ac1ae2 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -195,23 +195,10 @@ bool Loop::isSafeToClone() const {
     if (isa<IndirectBrInst>(BB->getTerminator()))
       return false;
 
-    if (const InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
-      if (II->cannotDuplicate())
-        return false;
-      // Return false if any loop blocks contain invokes to EH-pads other than
-      // landingpads;  we don't know how to split those edges yet.
-      auto *FirstNonPHI = II->getUnwindDest()->getFirstNonPHI();
-      if (FirstNonPHI->isEHPad() && !isa<LandingPadInst>(FirstNonPHI))
-        return false;
-    }
-    for (Instruction &I : *BB) {
-      if (const CallInst *CI = dyn_cast<CallInst>(&I)) {
-        if (CI->cannotDuplicate())
+    for (Instruction &I : *BB)
+      if (auto CS = CallSite(&I))
+        if (CS.cannotDuplicate())
           return false;
-      }
-      if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB))
-        return false;
-    }
   }
   return true;
 }
diff --git a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
index 310f41e..0e861b6 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -500,6 +500,11 @@ bool LoopUnswitch::processCurrentLoop() {
       if (!CS) continue;
       if (CS.hasFnAttr(Attribute::Convergent))
         return false;
+      // Return false if any loop blocks contain invokes whose predecessor edges
+      // we cannot split.
+      if (auto *II = dyn_cast<InvokeInst>(&I))
+        if (!II->getUnwindDest()->canSplitPredecessors())
+          return false;
     }
   }
 
diff --git a/llvm/test/Transforms/LoopUnroll/unroll-cleanuppad.ll b/llvm/test/Transforms/LoopUnroll/unroll-cleanuppad.ll
new file mode 100644
index 0000000..67f3194
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/unroll-cleanuppad.ll
@@ -0,0 +1,40 @@
+; RUN: opt -S -loop-unroll %s | FileCheck %s
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc18.0.0"
+
+define void @test1() personality i32 (...)* @__CxxFrameHandler3 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %phi = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
+  invoke void @callee(i32 %phi)
+          to label %for.inc unwind label %ehcleanup
+
+for.inc:                                          ; preds = %for.body
+  %inc = add nuw nsw i32 %phi, 1
+  %cmp = icmp slt i32 %inc, 3
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.inc
+  call void @dtor()
+  ret void
+
+ehcleanup:                                        ; preds = %for.body
+  %cp = cleanuppad within none []
+  call void @dtor() [ "funclet"(token %cp) ]
+  cleanupret from %cp unwind to caller
+}
+
+; CHECK-LABEL: define void @test1(
+; CHECK: invoke void @callee(i32 0
+
+; CHECK: invoke void @callee(i32 1
+
+; CHECK: invoke void @callee(i32 2
+
+declare void @callee(i32)
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @dtor()
-- 
2.7.4