Introduce isDesirableCastOp() which determines whether IR builder
and constant folding should produce constant expressions for a
given cast type. This mirrors what we do for binary operators.
Mark zext/sext as undesirable, which prevents most creations of such
constant expressions. This is still somewhat incomplete and there
are a few more places that can create zext/sext expressions.
This is part of the work for
https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179.
The reason for the odd result in the constantexpr-fneg.c test is
that initially the "a[]" global is created with an [0 x i32] type,
at which point the icmp expression cannot be folded. Later it is
replaced with an [1 x i32] global and the icmp gets folded away.
But at that point we no longer fold the zext.
to member naming a weak member to nullptr.
This fixes a miscompile where constant evaluation would incorrectly
determine that a weak member function pointer is never null.
In passing, also improve the diagnostics for constant evaluation of some
nearby cases.
References to different declarations of the same entity aren't different
values, so shouldn't have different representations.
Recommit of e6393ee813178e9d3306b8e3c6949a4f32f8a2cb, most recently
reverted in 9a33f027ac7d73e14ae287e78ab554142d1cbc8f due to a bug caused
by ObjCInterfaceDecls not propagating availability attributes along
their redeclaration chains; that bug was fixed in
e2d4174e9c66251d1b408234b53f53d0903c0285.
References to different declarations of the same entity aren't different
values, so shouldn't have different representations.
Recommit of e6393ee813178e9d3306b8e3c6949a4f32f8a2cb with fixed handling
for weak declarations. We now look for attributes on the most recent
declaration when determining whether a declaration is weak. (Second
recommit with further fixes for mishandling of weak declarations. Our
behavior here is fundamentally unsound -- see PR47663 -- but this
approach attempts to not make things worse.)
This makes the C++ ABI depend entirely on the target: MS ABI for -win32 triples,
Itanium otherwise. It's no longer possible to do weird combinations.
To be able to run a test with a specific ABI without constraining it to a
specific triple, new substitutions are added to lit: %itanium_abi_triple and
%ms_abi_triple can be used to get the current target triple adjusted to the
desired ABI. For example, if the test suite is running with the i686-pc-win32
target, %itanium_abi_triple will expand to i686-pc-mingw32.
Differential Revision: http://llvm-reviews.chandlerc.com/D2545
llvm-svn: 199250
