Branch folding invalidates liveness and disables liveness verification
on some targets.

llvm-svn: 153597

Extract the liveness verification into its own method.

This makes it possible to run the machine code verifier after liveness
information is no longer required to be valid.

llvm-svn: 153596

a bunch of comments for the various functions. No intended functionality change.

llvm-svn: 153595

Revert r153519: "ARMLoadStoreOptimizer invalidates register liveness."

These patches caused miscompilations in povray by turning off branch
folding's updating of live-in lists.

It turns out the the late scheduler depends on the live-in lists, even
if it doesn't need correct kill flags.

<rdar://problem/11139228>

llvm-svn: 153593

This avoids the silly double search:

  if (isLiveIn(Reg))
    removeLiveIn(Reg);

llvm-svn: 153592

Original commit message for r153521 (aka r153423):
Use the new range metadata in computeMaskedBits and add a new optimization to
instruction simplify that lets us remove an and when loding a boolean value.

llvm-svn: 153587

llvm-svn: 153579

GlobalOpt: If we have an inbounds GEP from a ConstantAggregateZero global that we just determined to be constant, replace all loads from it with a zero value.

llvm-svn: 153576

llvm-svn: 153574

llvm-svn: 153573

blocks in the function cloner. This removes the last case of trivially
dead code that I've been seeing in the wild getting inlined, analyzed,
re-inlined, optimized, only to be deleted. Nukes a FIXME from the
cleanup tests.

llvm-svn: 153572

llvm-svn: 153571

and not the rest of the member tag.

Fixes PR11695

llvm-svn: 153570

llvm-svn: 153567

llvm-svn: 153564

llvm-svn: 153558

llvm-svn: 153557

llvm-svn: 153556

llvm-svn: 153555

llvm-svn: 153554

imposes a constraint that GOT16 referring to a local symbol or HI16 has to be
followed immediately by a matching LO16 relocation.

llvm-svn: 153553

them as machine instructions. Directives ".set noat" and ".set at" are now
emitted only at the beginning and end of a function except in the case where
they are emitted to enclose .cpload with an immediate operand that doesn't fit
in 16-bit field or unaligned load/stores.

Also, make the following changes:
- Remove function isUnalignedLoadStore and use a switch-case statement to
  determine whether an instruction is an unaligned load or store.

- Define helper function CreateMCInst which generates an instance of an MCInst
  from an opcode and a list of operands.

llvm-svn: 153552

any side effects.

llvm-svn: 153551

llvm-svn: 153549

llvm-svn: 153543

llvm-svn: 153542

executable has been moved to another machine). If that's not available
(read-only or something), then exit gracefully.
<rdar://problem/11111686>

llvm-svn: 153538

llvm-svn: 153536

will always be tiny sets, so DenseSet is overkill (SmallSet won't work as we
need iteration support). 

llvm-svn: 153529

If EmitNOAT is true, directives ".set noat" and ".set at" are emitted at the
beginning and end of a function. 

llvm-svn: 153528

testing a) the wrong behavior or b) something that I'm already testing
in the new test.

llvm-svn: 153525

Fixes PR10105

llvm-svn: 153524

undefined behavior, which Rafael was kind enough to fix.

Original commit message for r153423:
Use the new range metadata in computeMaskedBits and add a new optimization to
instruction simplify that lets us remove an and when loding a boolean value.

llvm-svn: 153521

This pass tries to update kill flags, but there are still many bugs.
Passes after the load/store optimizer don't need accurate liveness, so
don't even try.

<rdar://problem/11101911>

llvm-svn: 153519

llvm-svn: 153518

Branch folding can use a register scavenger to update liveness
information when required. Don't do that if liveness information is
already invalid.

llvm-svn: 153517

llvm-svn: 153516

llvm-svn: 153513

Late optimization passes like branch folding and tail duplication can
transform the machine code in a way that makes it expensive to keep the
register liveness information up to date. There is a fuzzy line between
register allocation and late scheduling where the liveness information
degrades.

The MRI::tracksLiveness() flag makes the line clear: While true,
liveness information is accurate, and can be used for register
scavenging. Once the flag is false, liveness information is not
accurate, and can only be used as a hint.

Late passes generally don't need the liveness information, but they will
sometimes use the register scavenger to help update it. The scavenger
enforces strict correctness, and we have to spend a lot of code to
update register liveness that may never be used.

llvm-svn: 153511

llvm-svn: 153508