From fcb5402f028c080cb7e25bb7e974bbb4a793e650 Mon Sep 17 00:00:00 2001
From: Nico Weber <nicolasweber@gmx.de>
Date: Wed, 25 Feb 2015 16:25:00 +0000
Subject: [PATCH] Reland r230460 with a test fix for -Asserts builds.

Original CL description:
Produce less broken basic block sequences for __finally blocks.

The way cleanups (such as PerformSEHFinally) get emitted is that codegen
generates some initialization code, then calls the cleanup's Emit() with the
insertion point set to a good place, then the cleanup is supposed to emit its
stuff, and then codegen might tack in a jump or similar to where the insertion
point is after the cleanup.

The PerformSEHFinally cleanup tries to just stash away the block it's supposed
to codegen into, and then does codegen later, into that stashed block.  However,
after codegen'ing the __finally block, it used to set the insertion point to
the finally's continuation block (where the __finally cleanup goes when its body
is completed after regular, non-exceptional control flow).  That's not correct,
as that block can (and generally does) already ends in a jump.  Instead,
remember the insertion point that was current before the __finally got emitted,
and restore that.

Fixes two of the crashes in PR22553.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@230503 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGException.cpp           |  7 +++--
 test/CodeGen/exceptions-seh-finally.c | 42 +++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/lib/CodeGen/CGException.cpp b/lib/CodeGen/CGException.cpp
index 61f538b0ee..b7953bcedc 100644
--- a/lib/CodeGen/CGException.cpp
+++ b/lib/CodeGen/CGException.cpp
@@ -813,8 +813,8 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
   bool hasFilter = false;
   SmallVector<llvm::Value*, 4> filterTypes;
   llvm::SmallPtrSet<llvm::Value*, 4> catchTypes;
-  for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end();
-         I != E; ++I) {
+  for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E;
+       ++I) {
 
     switch (I->getKind()) {
     case EHScope::Cleanup:
@@ -1927,6 +1927,7 @@ void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S, SEHFinallyInfo &FI) {
     assert(FI.ContBB && "did not emit normal cleanup");
 
     // Emit the code into FinallyBB.
+    CGBuilderTy::InsertPoint SavedIP = Builder.saveIP();
     Builder.SetInsertPoint(FI.FinallyBB);
     EmitStmt(Finally->getBlock());
 
@@ -1949,7 +1950,7 @@ void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S, SEHFinallyInfo &FI) {
       Builder.CreateBr(FI.ContBB);
     }
 
-    Builder.SetInsertPoint(FI.ContBB);
+    Builder.restoreIP(SavedIP);
 
     return;
   }
diff --git a/test/CodeGen/exceptions-seh-finally.c b/test/CodeGen/exceptions-seh-finally.c
index 4cd82d0972..64b3ffdf18 100644
--- a/test/CodeGen/exceptions-seh-finally.c
+++ b/test/CodeGen/exceptions-seh-finally.c
@@ -160,3 +160,45 @@ void noreturn_finally() {
 // CHECK-NEXT: cleanup
 // CHECK: store i8 1, i8* %
 // CHECK: br label %[[finally]]
+
+int finally_with_return() {
+  __try {
+    return 42;
+  } __finally {
+  }
+}
+// CHECK-LABEL: define i32 @finally_with_return()
+// CHECK: store i8 0, i8* %
+// CHECK-NEXT: br label %[[finally:[^ ]*]]
+//
+// CHECK: [[finally]]
+// CHECK-NEXT: br label %[[finallycont:[^ ]*]]
+//
+// CHECK: [[finallycont]]
+// CHECK-NEXT: ret i32 42
+
+int nested___finally___finally() {
+  __try {
+    __try {
+    } __finally {
+      return 1;
+    }
+  } __finally {
+    // Intentionally no return here.
+  }
+  return 0;
+}
+// CHECK-LABEL: define i32 @nested___finally___finally
+// CHECK: store i8 0, i8* %
+// CHECK-NEXT: br label %[[finally:[^ ]*]]
+//
+// CHECK: [[finally]]
+// CHECK-NEXT:  store i32 1, i32* %
+// CHECK-NEXT:  store i8 0, i8* %
+// CHECK-NEXT: br label %[[outerfinally:[^ ]*]]
+//
+// CHECK: [[outerfinally]]
+// CHECK-NEXT: br label %[[finallycont:[^ ]*]]
+//
+// CHECK: [[finallycont]]
+// CHECK-NEXT: ret i32 1
-- 
2.40.0