From 1e45487dfde9de304f28e1fb49b3c15a036b9c00 Mon Sep 17 00:00:00 2001
From: Chad Rosier <mcrosier@apple.com>
Date: Tue, 5 Feb 2013 18:23:10 +0000
Subject: [PATCH] [SjLj Prepare] When demoting an invoke instructions to the
 stack, if the normal edge is critical, then split it so we can insert the
 store. rdar://13126179

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174418 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/DemoteRegToStack.cpp     | 20 ++++--
 .../CodeGen/ARM/sjlj-prepare-critical-edge.ll | 67 +++++++++++++++++++
 2 files changed, 82 insertions(+), 5 deletions(-)
 create mode 100644 test/CodeGen/ARM/sjlj-prepare-critical-edge.ll

diff --git a/lib/Transforms/Utils/DemoteRegToStack.cpp b/lib/Transforms/Utils/DemoteRegToStack.cpp
index d5c41f54594..db525cdc24d 100644
--- a/lib/Transforms/Utils/DemoteRegToStack.cpp
+++ b/lib/Transforms/Utils/DemoteRegToStack.cpp
@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/IR/Function.h"
@@ -78,12 +79,21 @@ AllocaInst *llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads,
     InsertPt = &I;
     ++InsertPt;
   } else {
-    // We cannot demote invoke instructions to the stack if their normal edge
-    // is critical.
     InvokeInst &II = cast<InvokeInst>(I);
-    assert(II.getNormalDest()->getSinglePredecessor() &&
-           "Cannot demote invoke with a critical successor!");
-    InsertPt = II.getNormalDest()->begin();
+    if (II.getNormalDest()->getSinglePredecessor())
+      InsertPt = II.getNormalDest()->getFirstInsertionPt();
+    else {
+      // We cannot demote invoke instructions to the stack if their normal edge
+      // is critical.  Therefore, split the critical edge and insert the store
+      // in the newly created basic block.
+      unsigned SuccNum = GetSuccessorNumber(I.getParent(), II.getNormalDest());
+      TerminatorInst *TI = &cast<TerminatorInst>(I);
+      assert (isCriticalEdge(TI, SuccNum) &&
+              "Expected a critical edge!");
+      BasicBlock *BB = SplitCriticalEdge(TI, SuccNum);
+      assert (BB && "Unable to split critical edge.");
+      InsertPt = BB->getFirstInsertionPt();
+    }
   }
 
   for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt)
diff --git a/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll b/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
new file mode 100644
index 00000000000..d8241d0dc38
--- /dev/null
+++ b/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
@@ -0,0 +1,67 @@
+; RUN: llc < %s -O1 -mtriple thumbv7-apple-ios6
+; Just make sure no one tries to make the assumption that the normal edge of an
+; invoke is never a critical edge.  Previously, this code would assert.
+
+%struct.__CFString = type opaque
+
+declare void @bar(%struct.__CFString*, %struct.__CFString*)
+
+define noalias i8* @foo(i8* nocapture %inRefURL) noreturn ssp {
+entry:
+  %call = tail call %struct.__CFString* @bar3()
+  %call2 = invoke i8* @bar2()
+          to label %for.cond unwind label %lpad
+
+for.cond:                                         ; preds = %entry, %for.cond
+  invoke void @bar(%struct.__CFString* undef, %struct.__CFString* null)
+          to label %for.cond unwind label %lpad5
+
+lpad:                                             ; preds = %entry
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*)
+          cleanup
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = extractvalue { i8*, i32 } %0, 1
+  br label %ehcleanup
+
+lpad5:                                            ; preds = %for.cond
+  %3 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*)
+          cleanup
+  %4 = extractvalue { i8*, i32 } %3, 0
+  %5 = extractvalue { i8*, i32 } %3, 1
+  invoke void @release(i8* %call2)
+          to label %ehcleanup unwind label %terminate.lpad.i.i16
+
+terminate.lpad.i.i16:                             ; preds = %lpad5
+  %6 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*)
+          catch i8* null
+  tail call void @terminatev() noreturn nounwind
+  unreachable
+
+ehcleanup:                                        ; preds = %lpad5, %lpad
+  %exn.slot.0 = phi i8* [ %1, %lpad ], [ %4, %lpad5 ]
+  %ehselector.slot.0 = phi i32 [ %2, %lpad ], [ %5, %lpad5 ]
+  %7 = bitcast %struct.__CFString* %call to i8*
+  invoke void @release(i8* %7)
+          to label %_ZN5SmartIPK10__CFStringED1Ev.exit unwind label %terminate.lpad.i.i
+
+terminate.lpad.i.i:                               ; preds = %ehcleanup
+  %8 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_sj0 to i8*)
+          catch i8* null
+  tail call void @terminatev() noreturn nounwind
+  unreachable
+
+_ZN5SmartIPK10__CFStringED1Ev.exit:               ; preds = %ehcleanup
+  %lpad.val = insertvalue { i8*, i32 } undef, i8* %exn.slot.0, 0
+  %lpad.val12 = insertvalue { i8*, i32 } %lpad.val, i32 %ehselector.slot.0, 1
+  resume { i8*, i32 } %lpad.val12
+}
+
+declare %struct.__CFString* @bar3()
+
+declare i8* @bar2()
+
+declare i32 @__gxx_personality_sj0(...)
+
+declare void @release(i8*)
+
+declare void @terminatev()