testcase test/Regression/Assembler/ConstantExprFold.llx
Note that these kinds of things only rarely show up in source code, but are
exceedingly common in the intermediate stages of algorithms like SCCP. By
folding things (especially relational operators) that use symbolic constants,
we are able to speculatively fold more conditional branches, which can
lead to some big simplifications.
It would be easy to add a lot more special cases here, so if you notice
SCCP missing anything "obvious", you know what to make smarter. :)
llvm-svn: 10812
Move a bunch of (now) private stuff from ConstantFolding.h into
ConstantFolding.cpp.
This _finally_ gets us to a place where we have a sane constant folder. The
rules are:
1. LLVM clients now use ConstantExpr::get* methods to fold constants. If they
cannot be folded, a constantexpr is created, so these methods always return
valid Constant*'s.
2. The implementation of ConstantExpr::get* uses the functions exposed by
ConstantFolding.h to try to fold constants. If they cannot be folded,
they should return a null pointer.
3. The implementation of ConstantFolding can do whatever it wants, and only
has one client (Constants.cpp)
This cuts down on the wierd dependencies, and eliminates the two interfaces.
The old constanthandling interface was especially bad for clients to use
because almost none of them took the failure condition into consideration,
thus leading to obscure problems.
llvm-svn: 10807
