From 37497377a80f86709b7b3934c2aeca0b527617ca Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Thu, 22 Jan 2015 02:25:56 +0000
Subject: [PATCH] SEH: Emit the constant filter 1 as a catch-all

Minor optimization of code like __try { ... } __except(1) { ... }.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226766 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGException.cpp   | 12 ++++++++++++
 test/CodeGen/exceptions-seh.c | 12 +++++-------
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/lib/CodeGen/CGException.cpp b/lib/CodeGen/CGException.cpp
index 94cfca962d..68764e9260 100644
--- a/lib/CodeGen/CGException.cpp
+++ b/lib/CodeGen/CGException.cpp
@@ -1839,6 +1839,18 @@ void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
   SEHExceptStmt *Except = S.getExceptHandler();
   assert(Except);
   EHCatchScope *CatchScope = EHStack.pushCatch(1);
+
+  // If the filter is known to evaluate to 1, then we can use the clause "catch
+  // i8* null".
+  llvm::Constant *C =
+      CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this);
+  if (C && C->isOneValue()) {
+    CatchScope->setCatchAllHandler(0, createBasicBlock("__except"));
+    return;
+  }
+
+  // In general, we have to emit an outlined filter function. Use the function
+  // in place of the RTTI typeinfo global that C++ EH uses.
   CodeGenFunction FilterCGF(CGM, /*suppressNewContext=*/true);
   llvm::Function *FilterFunc =
       FilterCGF.GenerateSEHFilterFunction(*this, *Except);
diff --git a/test/CodeGen/exceptions-seh.c b/test/CodeGen/exceptions-seh.c
index ebf1cfbb2b..bba5eac36c 100644
--- a/test/CodeGen/exceptions-seh.c
+++ b/test/CodeGen/exceptions-seh.c
@@ -26,13 +26,11 @@ int safe_div(int numerator, int denominator, int *res) {
 //
 // CHECK: [[lpad]]
 // CHECK: landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*)
-// CHECK: %[[sel:[^ ]*]] = load i32*
-// CHECK: %[[filt_id:[^ ]*]] = call i32 @llvm.eh.typeid.for(i8* bitcast (i32 (i8*, i8*)* @"\01?filt$0@0@safe_div@@" to i8*))
-// CHECK: %[[matches:[^ ]*]] = icmp eq i32 %[[sel]], %[[filt_id]]
-// CHECK: br i1 %[[matches]], label %[[except_bb:[^ ]*]], label %{{.*}}
-//
-// CHECK: [[except_bb]]
-// CHECK: store i32 -42, i32* %[[success:[^ ]*]]
+// CHECK-NEXT: catch i8* null
+// CHECK-NOT: br i1
+// CHECK: br label %[[except:[^ ]*]]
+// CHECK: [[except]]
+// CHECK-NEXT: store i32 -42, i32* %[[success:[^ ]*]]
 //
 // CHECK: %[[res:[^ ]*]] = load i32* %[[success]]
 // CHECK: ret i32 %[[res]]
-- 
2.40.0