as unsigned divisions.  Same caveats as before.

llvm-svn: 60284

multiplies.

Some more cleverness would be nice, though. It would be nice if we 
could do this transformation on illegal types.  Also, we would 
prefer a narrower constant when possible so that we can use a narrower
multiply, which can be cheaper.

llvm-svn: 60283

llvm-svn: 60282

llvm-svn: 60281

This fixes PR3127
http://llvm.org/bugs/show_bug.cgi?id=3127

llvm-svn: 60280

llvm-svn: 60279

"For signed integers, the determination of overflow of x*y is not so simple. If
x and y have the same sign, then overflow occurs iff xy > 2**31 - 1. If they
have opposite signs, then overflow occurs iff xy < -2**31."

In this case, x == -1.

llvm-svn: 60278

nearby FIXME.

I'm not sure what the right way to fix the Cell test was; if the 
approach I used isn't okay, please let me know.

llvm-svn: 60277

llvm-svn: 60276

overflowed on negation. This commit checks to make sure that neithe C nor X
overflows. This requires that the RHS of X (a subtract instruction) be a
constant integer.

llvm-svn: 60275

ReverseLocalDeps when we update it.  This fixes a regression test
failure from my last commit.

Second, for each non-local cached information structure, keep a bit that
indicates whether it is dirty or not.  This saves us a scan over the whole
thing in the common case when it isn't dirty.

llvm-svn: 60274

Hopefully this doesn't break anyone else's build... it shouldn't unless 
the MinGW variable means something other than compiling with MinGW.

llvm-svn: 60273

llvm-svn: 60272

instead of containing them by value.  This increases the density
(!) of NonLocalDeps as well as making the reallocation case 
faster.  This speeds up gvn on 403.gcc by 2% and makes room for
future improvements.

I'm not super thrilled with having to explicitly manage the new/delete
of the map, but it is necesary for the next change.

llvm-svn: 60271

initializers.  llvm-gcc appears to be more aggressive, but incorrect, 
for constructs like "const int a[] = {1,2,3};"; that said, current 
optimizers will do the appropriate optimizations when safe.

llvm-svn: 60270

llvm-svn: 60269

llvm-svn: 60268

If we see that a load depends on the allocation of its memory with no
intervening stores, we now return a 'None' depedency instead of "Normal".
This tweaks GVN to do its optimization with the new result.

llvm-svn: 60267

method that returns its result as a DepResultTy instead of as a
MemDepResult.  This reduces conversion back and forth.

llvm-svn: 60266

the file, no functionality change.

llvm-svn: 60265

comments about what this class does.

llvm-svn: 60264

dependencies.  The basic situation was this: consider if we had:

  store1
  ...
  store2
  ...
  store3

Where memdep thinks that store3 depends on store2 and store2 depends 
on store1.  The problem happens when we delete store2: The code in 
question was updating dep info for store3 to be store1.  This is a
spiffy optimization, but is not safe at all, because aliasing isn't
transitive.  This bug isn't exposed today with DSE because DSE will only
zap store2 if it is identifical to store 3, and in this case, it is 
safe to update it to depend on store1.  However, memcpyopt is not so
fortunate, which is presumably why the "dropInstruction" code used to
exist.

Since this doesn't actually provide a speedup in practice, just rip the
code out.

llvm-svn: 60263

llvm-svn: 60262

already declared in the other headers.

llvm-svn: 60261

Fix a subtle iterator invalidation bug I introduced in the last commit.

llvm-svn: 60258

llvm-svn: 60257

an entry in the nonlocal deps map, don't reset entries
referencing that instruction to [dirty, null], instead, set
them to [dirty,next] where next is the instruction after the
deleted one.  Use this information in the non-local deps
code to avoid rescanning entire blocks.

This speeds up GVN slightly by avoiding pointless work.  On
403.gcc this makes GVN 1.5% faster. 

llvm-svn: 60256

a smallvector instead of a DenseMap.  This speeds up GVN by 5%
on 403.gcc.

llvm-svn: 60255

no functionality/code change.

llvm-svn: 60254

formulation that is faster and doesn't require nonLazyHelper.
Much less code.

llvm-svn: 60253

test return the loaded value.

llvm-svn: 60252

llvm-svn: 60251

llvm-svn: 60250

llvm-svn: 60249

llvm-svn: 60248

llvm-svn: 60243

llvm-svn: 60242

llvm-svn: 60241

Put a some code back to handle buggy behavior that GVN expects: it wants
loads to depend on each other, and accesses to depend on their allocations.

llvm-svn: 60240

llvm-svn: 60239