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Fix argument expansion of reference fields of structs 

r268261 made Clang "expand" more struct arguments on Windows. It removed
the check for 'RD->isCLike()', which was preventing us from attempting
to expand structs with reference type fields.

Our expansion code was attempting to load and pass each field of the
type in turn. We were accidentally doing one to many loads on reference
type fields.

On the function prologue side, we can use
EmitLValueForFieldInitialization, which obviously gets the address of
the field. On the call side, I tweaked EmitRValueForField directly,
since this is the only use of this method.

Fixes PR27607

llvm-svn: 268321
This commit is contained in:
Reid Kleckner 2016-05-02 22:42:34 +00:00
parent d5a3b23736
commit 9d03109233
3 changed files with 27 additions and 1 deletions
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2
clang/lib/CodeGen/CGCall.cpp
View File

@ -948,7 +948,7 @@ void CodeGenFunction::ExpandTypeFromArgs(
}
for (auto FD : RExp->Fields) {
// FIXME: What are the right qualifiers here?
LValue SubLV = EmitLValueForField(LV, FD);
LValue SubLV = EmitLValueForFieldInitialization(LV, FD);
ExpandTypeFromArgs(FD->getType(), SubLV, AI);
}
} else if (isa<ComplexExpansion>(Exp.get())) {

4
clang/lib/CodeGen/CGExpr.cpp
View File

@ -3667,6 +3667,10 @@ RValue CodeGenFunction::EmitRValueForField(LValue LV,
case TEK_Aggregate:
return FieldLV.asAggregateRValue();
case TEK_Scalar:
// This routine is used to load fields one-by-one to perform a copy, so
// don't load reference fields.
if (FD->getType()->isReferenceType())
return RValue::get(FieldLV.getPointer());
return EmitLoadOfLValue(FieldLV, Loc);
}
llvm_unreachable("bad evaluation kind");

22
clang/test/CodeGenCXX/microsoft-abi-sret-and-byval.cpp
View File

@ -217,6 +217,28 @@ void big_arg(Big s) {}
// WIN32: define void @"\01?big_arg@@YAXUBig@@@Z"(%struct.Big* byval align 4 %s)
// WIN64: define void @"\01?big_arg@@YAXUBig@@@Z"(%struct.Big* %s)
// PR27607: We would attempt to load i32 value out of the reference instead of
// just loading the pointer from the struct during argument expansion.
struct RefField {
RefField(int &x);
int &x;
};
void takes_ref_field(RefField s) {}
// LINUX-LABEL: define void @_Z15takes_ref_field8RefField(%struct.RefField* byval align 4 %s)
// WIN32: define void @"\01?takes_ref_field@@YAXURefField@@@Z"(i32* %s.0)
// WIN64: define void @"\01?takes_ref_field@@YAXURefField@@@Z"(i64 %s.coerce)
void pass_ref_field() {
int x;
takes_ref_field(RefField(x));
}
// LINUX-LABEL: define void @_Z14pass_ref_fieldv()
// LINUX: call void @_Z15takes_ref_field8RefField(%struct.RefField* byval align 4 %{{.*}})
// WIN32-LABEL: define void @"\01?pass_ref_field@@YAXXZ"()
// WIN32: call void @"\01?takes_ref_field@@YAXURefField@@@Z"(i32* %{{.*}})
// WIN64-LABEL: define void @"\01?pass_ref_field@@YAXXZ"()
// WIN64: call void @"\01?takes_ref_field@@YAXURefField@@@Z"(i64 %{{.*}})
class Class {
public:
Small thiscall_method_small() { return Small(); }