[PATCH] D13223: Generate assume loads only with -fstrict-vtable-pointers

[Piotr Padlewski via cfe-commits]

Prazek created this revision.
Prazek added reviewers: rsmith, samsonov, majnemer.
Prazek added a subscriber: cfe-commits.

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

http://reviews.llvm.org/D13223

Files:
  lib/CodeGen/CGClass.cpp
  test/CodeGenCXX/vtable-assume-load.cpp

Index: test/CodeGenCXX/vtable-assume-load.cpp
===================================================================
--- test/CodeGenCXX/vtable-assume-load.cpp
+++ 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
Index: lib/CodeGen/CGClass.cpp
===================================================================
--- lib/CodeGen/CGClass.cpp
+++ lib/CodeGen/CGClass.cpp
@@ -2107,9 +2107,12 @@
   // 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. Assumption loads requires -fstrict-vtable-pointers temporary.
   if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
       ClassDecl->isDynamicClass() && Type != Ctor_Base &&
-      CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl))
+      CGM.getCXXABI().canSpeculativelyEmitVTable(ClassDecl) &&
+      CGM.getCodeGenOpts().StrictVTablePointers)
     EmitVTableAssumptionLoads(ClassDecl, This);
 }
 


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