r234033 - [i386 ABI] expand small C like structs in C++, just like how we handle small

[Manman Ren]

Author: mren
Date: Fri Apr  3 13:10:29 2015
New Revision: 234033

URL: http://llvm.org/viewvc/llvm-project?rev=234033&view=rev
Log:
[i386 ABI] expand small C like structs in C++, just like how we handle small
C structs.

This comes up when we have a function that takes a struct and is defined in a
C++ file and used in a C file.

Before this commit, we will generate byval for C++ and will expand the struct
for C, thus causing difference at IR level. We will use bitcast of function type
at the callsite, which causes the inliner to not inline the function.

This commit changes how we handle small C like structs at IR level, but at
backend, we should generate the same argument passing before and after the
commit.

Note that the condition for expanding is still over conservative. We should be
able to expand type that is spelled with “class” and types that are not C-like.
But this commit fixes the inconsistent argument passing between C/C++.

Reviewed by John.

rdar://20121030

Modified:
    cfe/trunk/lib/CodeGen/TargetInfo.cpp
    cfe/trunk/test/CodeGenCXX/call-with-static-chain.cpp
    cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp

Modified: cfe/trunk/lib/CodeGen/TargetInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/TargetInfo.cpp?rev=234033&r1=234032&r2=234033&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/TargetInfo.cpp (original)
+++ cfe/trunk/lib/CodeGen/TargetInfo.cpp Fri Apr  3 13:10:29 2015
@@ -339,9 +339,15 @@ static bool canExpandIndirectArgument(Qu
   //
   // FIXME: This needs to be generalized to handle classes as well.
   const RecordDecl *RD = RT->getDecl();
-  if (!RD->isStruct() || isa<CXXRecordDecl>(RD))
+  if (!RD->isStruct())
     return false;
 
+  // We try to expand CLike CXXRecordDecl.
+  if (const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
+    if (!CXXRD->isCLike())
+      return false;
+  }
+
   uint64_t Size = 0;
 
   for (const auto *FD : RD->fields()) {

Modified: cfe/trunk/test/CodeGenCXX/call-with-static-chain.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/call-with-static-chain.cpp?rev=234033&r1=234032&r2=234033&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/call-with-static-chain.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/call-with-static-chain.cpp Fri Apr  3 13:10:29 2015
@@ -21,7 +21,7 @@ A &f4();
 void test() {
   A a;
 
-  // CHECK32: call i32 bitcast (i32 (%struct.A*, %struct.A*, %struct.A*, %struct.A*)* @f1 to i32 (i8*, %struct.A*, %struct.A*, %struct.A*, %struct.A*)*)(i8* nest bitcast (i32 (%struct.A*, %struct.A*, %struct.A*, %struct.A*)* @f1 to i8*)
+  // CHECK32: call i32 bitcast (i32 (i32, i32, i32, i32, i32, i32, i32, i32)* @f1 to i32 (i8*, i32, i32, i32, i32, i32, i32, i32, i32)*)(i8* nest bitcast (i32 (i32, i32, i32, i32, i32, i32, i32, i32)* @f1 to i8*)
   // CHECK64: call i32 bitcast (i32 (i64, i64, i64, i64, i64, i64, %struct.A*)* @f1 to i32 (i8*, i64, i64, i64, i64, i64, i64, %struct.A*)*)(i8* nest bitcast (i32 (i64, i64, i64, i64, i64, i64, %struct.A*)* @f1 to i8*)
   __builtin_call_with_static_chain(f1(a, a, a, a), f1);
 

Modified: cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp?rev=234033&r1=234032&r2=234033&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp Fri Apr  3 13:10:29 2015
@@ -101,12 +101,12 @@ Big big_return() { return Big(); }
 
 
 void small_arg(Small s) {}
-// LINUX-LABEL: define void @_Z9small_arg5Small(%struct.Small* byval align 4 %s)
+// LINUX-LABEL: define void @_Z9small_arg5Small(i32 %s.0)
 // WIN32: define void @"\01?small_arg@@YAXUSmall@@@Z"(%struct.Small* byval align 4 %s)
 // WIN64: define void @"\01?small_arg@@YAXUSmall@@@Z"(i32 %s.coerce)
 
 void medium_arg(Medium s) {}
-// LINUX-LABEL: define void @_Z10medium_arg6Medium(%struct.Medium* byval align 4 %s)
+// LINUX-LABEL: define void @_Z10medium_arg6Medium(i32 %s.0, i32 %s.1)
 // WIN32: define void @"\01?medium_arg@@YAXUMedium@@@Z"(%struct.Medium* byval align 4 %s)
 // WIN64: define void @"\01?medium_arg@@YAXUMedium@@@Z"(i64 %s.coerce)
 
@@ -229,7 +229,7 @@ class Class {
   // WIN64: define linkonce_odr void @"\01?thiscall_method_arg at Class@@QEAAXUEmptyWithCtor@@@Z"(%class.Class* %this, i8 %s.coerce)
 
   void thiscall_method_arg(Small s) {}
-  // LINUX: define {{.*}} void @_ZN5Class19thiscall_method_argE5Small(%class.Class* %this, %struct.Small* byval align 4 %s)
+  // LINUX: define {{.*}} void @_ZN5Class19thiscall_method_argE5Small(%class.Class* %this, i32 %s.0)
   // WIN32: define {{.*}} void @"\01?thiscall_method_arg at Class@@QAEXUSmall@@@Z"(%class.Class* %this, %struct.Small* byval align 4 %s)
   // WIN64: define linkonce_odr void @"\01?thiscall_method_arg at Class@@QEAAXUSmall@@@Z"(%class.Class* %this, i32 %s.coerce)