llvm-svn: 131862

result is non-zero.  Implement an example optimization (PR9814), which allows us to
transform:
  A / ((1 << B) >>u 2)
into:
  A >>u (B-2)

which we compile into:

_divu3:                                 ## @divu3
	leal	-2(%rsi), %ecx
	shrl	%cl, %edi
	movl	%edi, %eax
	ret

instead of:

_divu3:                                 ## @divu3
	movb	%sil, %cl
	movl	$1, %esi
	shll	%cl, %esi
	shrl	$2, %esi
	movl	%edi, %eax
	xorl	%edx, %edx
	divl	%esi, %eax
	ret

llvm-svn: 131860

failing to form a memset, then having to delete it" but my approximation
isn't safe for self recurrent loops.  Instead of doign a hack, just
do it the right way.

llvm-svn: 131858

Add a parameter to ConstantFoldTerminator() that callers can use to ask it to also clean up the condition of any conditional terminator it folds to be unconditional, if that turns the condition into dead code. This just means it calls RecursivelyDeleteTriviallyDeadInstructions() in strategic spots. It defaults to the old behavior.

I also changed -simplifycfg, -jump-threading and -codegenprepare to use this to produce slightly better code without any extra cleanup passes (AFAICT this was the only place in -simplifycfg where now-dead conditions of replaced terminators weren't being cleaned up). The only other user of this function is -sccp, but I didn't read that thoroughly enough to figure out whether it might be holding pointers to instructions that could be deleted by this.

llvm-svn: 131855

"stored once" even if its address is compared.

llvm-svn: 131849

causing it to get into infinite loops when it would widen a 
load (which can necessarily leave around dead loads).

llvm-svn: 131847

of the inlinee to the code representing the original function.

llvm-svn: 131838

consistently.

llvm-svn: 131803

It's better to do this in codegen, mul.with.overflow(X, 2) is more canonical because it has only one use on "X".

llvm-svn: 131798

llvm-svn: 131789

No functionality enabled by default. Use -disable-iv-rewrite.
Extended IVUsers to keep track of the phi that represents the users' IV.
Added the WidenIV transform to replace a narrow IV with a wide IV
by doing a one-for-one replacement of IV users instead of expanding the
SCEV expressions. [sz]exts are removed and truncs are inserted.

llvm-svn: 131744

llvm-svn: 131716

llvm-svn: 131708

Reapply r131605. This time with a fix, which is to use NoFolder.

llvm-svn: 131673

llvm-svn: 131659

llvm-svn: 131620

I'm not sure this is quite ideal, but I can't really think of any better way to do it.

llvm-svn: 131616

llvm-svn: 131609

llvm-svn: 131607

llvm-svn: 131605

llvm-svn: 131604

llvm-svn: 131598

llvm-svn: 131596

llvm-svn: 131580

of the comparison, so that the resulting expression is fully
normalized. This fixes PR9939.

llvm-svn: 131576

llvm-svn: 131571

llvm-svn: 131566

llvm-svn: 131561

llvm-svn: 131559

llvm-svn: 131552

llvm-svn: 131551

llvm-svn: 131548

llvm-svn: 131547

llvm-svn: 131545

llvm-svn: 131544

llvm-svn: 131543

llvm-svn: 131542

llvm-svn: 131541

llvm-svn: 131538

Original log entry:
Refactor getActionType and getTypeToTransformTo ; place all of the 'decision'
code in one place.

llvm-svn: 131536