From: Piotr Padlewski <prazek@google.com>
Date: Mon, 28 Sep 2015 20:30:22 +0000 (+0000)
Subject: Generate assume loads only with -fstrict-vtable-pointers
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bfa22743ff0f050462c38d3e9d1b575563300133;p=clang

Generate assume loads only with -fstrict-vtable-pointers

Temporary fix till InstCombine and other possible passes will be
efficient to handle multiple assumes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@248734 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index 7d55685767..6394d1ff17 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -2107,9 +2107,12 @@ void CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
   // FIXME: If vtable is used by ctor/dtor, or if vtable is external and we are
   // sure that definition of vtable is not hidden,
   // then we are always safe to refer to it.
+  // FIXME: It looks like InstCombine is very inefficient on dealing with
+  // assumes. Make assumption loads require -fstrict-vtable-pointers temporarily.
   if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
       ClassDecl->isDynamicClass() && Type != Ctor_Base &&
-      CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl))
+      CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl) &&
+      CGM.getCodeGenOpts().StrictVTablePointers)
     EmitVTableAssumptionLoads(ClassDecl, This);
 }
 
diff --git a/test/CodeGenCXX/vtable-assume-load.cpp b/test/CodeGenCXX/vtable-assume-load.cpp
index 072be285b2..30cfc00ec7 100644
--- a/test/CodeGenCXX/vtable-assume-load.cpp
+++ b/test/CodeGenCXX/vtable-assume-load.cpp
@@ -1,5 +1,6 @@
-// RUN: %clang_cc1 %s -triple x86_64-apple-darwin10 -emit-llvm -o %t.ll -O1 -disable-llvm-optzns -fms-extensions
-// RUN: %clang_cc1 %s -triple i686-pc-win32 -emit-llvm -o %t.ms.ll -O1 -disable-llvm-optzns -fms-extensions
+// RUN: %clang_cc1 %s -triple x86_64-apple-darwin10 -emit-llvm -o %t.ll -O1 -disable-llvm-optzns -fms-extensions -fstrict-vtable-pointers
+// RUN: %clang_cc1 %s -triple i686-pc-win32 -emit-llvm -o %t.ms.ll -O1 -disable-llvm-optzns -fms-extensions -fstrict-vtable-pointers
+// FIXME: Assume load should not require -fstrict-vtable-pointers
 
 // RUN: FileCheck --check-prefix=CHECK1 --input-file=%t.ll %s
 // RUN: FileCheck --check-prefix=CHECK2 --input-file=%t.ll %s