the back-edge block, we must check the preincremented value.

llvm-svn: 12968

Instead of producing code like this:

Loop:
  X = phi 0, X2
  ...

  X2 = X + 1
  if (X != N-1) goto Loop

We now generate code that looks like this:

Loop:
  X = phi 0, X2
  ...

  X2 = X + 1
  if (X2 != N) goto Loop

This has two big advantages:
  1. The trip count of the loop is now explicit in the code, allowing
     the direct implementation of Loop::getTripCount()
  2. This reduces register pressure in the loop, and allows X and X2 to be
     put into the same register.

As a consequence of the second point, the code we generate for loops went
from:

.LBB2:  # no_exit.1
	...
        mov %EDI, %ESI
        inc %EDI
        cmp %ESI, 2
        mov %ESI, %EDI
        jne .LBB2 # PC rel: no_exit.1

To:

.LBB2:  # no_exit.1
	...
        inc %ESI
        cmp %ESI, 3
        jne .LBB2 # PC rel: no_exit.1

... which has two fewer moves, and uses one less register.

llvm-svn: 12961

llvm-svn: 12940

test/Regression/Transforms/SCCP/calltest.ll

llvm-svn: 12921

llvm-svn: 12917

LoopSimplify was not updating dominator frontiers correctly in some cases.

llvm-svn: 12890

llvm-svn: 12888

This is fairly straight-forward, but was a real nightmare to get just
perfect.  aarg.  :)

llvm-svn: 12884

llvm-svn: 12858

llvm-svn: 12826

llvm-svn: 12824

llvm-svn: 12821

Canonicalize add of sign bit constant into a xor

llvm-svn: 12819

and a bit more powerful

llvm-svn: 12817

llvm-svn: 12816

llvm-svn: 12814

llvm-svn: 12813

llvm-svn: 12811

llvm-svn: 12810

call and invoke instructions that are known to not write to memory.

llvm-svn: 12807

This transforms code like this:

   %C = or %A, %B
   %D = select %cond, %C, %A
into:
   %C = select %cond, %B, 0
   %D = or %A, %C

Since B is often a constant, the select can often be eliminated.  In any case,
this reduces the usage count of A, allowing subsequent optimizations to happen.

This xform applies when the operator is any of:
  add, sub, mul, or, xor, and, shl, shr

llvm-svn: 12800

that have a constant operand.  This implements
add.ll:test19, shift.ll:test15*, and others that are not tested

llvm-svn: 12794

llvm-svn: 12793

llvm-svn: 12784

llvm-svn: 12769

llvm-svn: 12762

llvm-svn: 12659

llvm-svn: 12658

types and can have arbitrary 32- and 64-bit integer types indexing into
sequential types.

llvm-svn: 12653

This also implements some new features for the indvars pass, including
linear function test replacement, exit value substitution, and it works with
a much more general class of induction variables and loops.

llvm-svn: 12620

llvm-svn: 12595

Testcase: LoopSimplify/2004-04-01-IncorrectDomUpdate.ll

llvm-svn: 12592

llvm-svn: 12573

llvm-svn: 12544

llvm-svn: 12540

llvm-svn: 12520

#1 is to unconditionally strip constantpointerrefs out of
instruction operands where they are absolutely pointless and inhibit
optimization.  GRRR!

#2 is to implement InstCombine/getelementptr_const.ll

llvm-svn: 12519

llvm-svn: 12507

llvm-svn: 12464

llvm-svn: 12458