objc IRGen: force CSE of load of ivar offsets by setting

the 'invariant.load' metadata tag onto those loads.
// rdar://10840980

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150994 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index d42f9f27fa3028a72b4dac6a70cc6c5313fcb6f6..9e3f7d7b22a2199473ab55290842c5dbe40003a1 100644 (file)
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -5704,8 +5704,13 @@ LValue CGObjCNonFragileABIMac::EmitObjCValueForIvar(
                                                const ObjCIvarDecl *Ivar,
                                                unsigned CVRQualifiers) {
   ObjCInterfaceDecl *ID = ObjectTy->getAs<ObjCObjectType>()->getInterface();
+  llvm::Value *Offset = EmitIvarOffset(CGF, ID, Ivar);
+  if (llvm::LoadInst *LI = dyn_cast<llvm::LoadInst>(Offset))
+    LI->setMetadata(CGM.getModule().getMDKindID("invariant.load"), 
+                   llvm::MDNode::get(VMContext,
+                   ArrayRef<llvm::Value*>()));
   return EmitValueForIvarAtOffset(CGF, ID, BaseValue, Ivar, CVRQualifiers,
-                                  EmitIvarOffset(CGF, ID, Ivar));
+                                  Offset);
 }
 
 llvm::Value *CGObjCNonFragileABIMac::EmitIvarOffset(

diff --git a/test/CodeGenObjC/ivar-base-as-invariant-load.m b/test/CodeGenObjC/ivar-base-as-invariant-load.m
new file mode 100644 (file)
index 0000000..8b660cf
--- /dev/null
+++ b/test/CodeGenObjC/ivar-base-as-invariant-load.m
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -emit-llvm  -triple x86_64-apple-darwin -x objective-c %s -o - | FileCheck %s
+// rdar://10840980
+
+@interface A {
+        struct {
+                unsigned char a : 1;
+                unsigned char b : 1;
+                unsigned char c : 1;
+        } _flags;
+}
+
+@end
+
+@implementation A
+
+- (id)init {
+        _flags.a = 1;
+        _flags.b = 1;
+        _flags.c = 1;
+
+        return self;
+}
+
+@end
+
+// CHECK: [[T1:%.*]] = load i64* @"OBJC_IVAR_$_A._flags", !invariant.load !4
+// CHECK: [[T2:%.*]] = load i64* @"OBJC_IVAR_$_A._flags", !invariant.load !4
+// CHECK: [[T3:%.*]] = load i64* @"OBJC_IVAR_$_A._flags", !invariant.load !4
+