https://bugs.llvm.org/show_bug.cgi?id=47499
Bug ID: 47499
Summary: __unaligned extension inconsistent behaviour with C
and C++
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: rofir...@gmail.com
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
struct Foo {
unsigned long x;
};
void foo(__unaligned struct Foo* out){
out->x = 5;
}
Emits this in C (which is the expected behaviour)
%struct.Foo = type { i64 }
define dso_local void @foo(%struct.Foo* nocapture %0) local_unnamed_addr #0 {
%2 = getelementptr inbounds %struct.Foo, %struct.Foo* %0, i64 0, i32 0
store i64 5, i64* %2, align 1, !tbaa !2
ret void
}
but this in C++ which does not honour the qualifier
%struct.Foo = type { i64 }
define dso_local void @_Z3fooPU11__unaligned3Foo(%struct.Foo* nocapture %0)
local_unnamed_addr #0 {
%2 = getelementptr inbounds %struct.Foo, %struct.Foo* %0, i64 0, i32 0
store i64 5, i64* %2, align 8, !tbaa !2
ret void
}
We want both languages agree. I suggest we bring the current behaviour in C to
C++.
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