%reg1025 = <sext> %reg1024
    ...
   %reg1026 = SUBREG_TO_REG 0, %reg1024, 4

into this:

   %reg1025 = <sext> %reg1024
    ...
   %reg1027 = EXTRACT_SUBREG %reg1025, 4
   %reg1026 = SUBREG_TO_REG 0, %reg1027, 4

The problem here is that SUBREG_TO_REG is there to assert that an implicit zext
occurs. It doesn't insert a zext instruction. If we allow the EXTRACT_SUBREG
here, it will give us the value after the <sext>, not the original value of
%reg1024 before <sext>.

llvm-svn: 105741

llvm-svn: 105665

that it is an immediate before checking that the instruction is an
EXTRACT_SUBREG.

llvm-svn: 105585

llvm-svn: 105561

llvm-svn: 105554

llvm-svn: 105541

llvm-svn: 105511

I don't think this ever resulted in problems on x86, but it
would on ARM.

llvm-svn: 105509

llvm-svn: 105502

llvm-svn: 105498

llvm-svn: 105492

llvm-svn: 105481

register allocation.

Process all of the clobber lists at the end of the function, marking the
registers as used in MachineRegisterInfo.

This is necessary in case the calls clobber callee-saved registers (sic).

llvm-svn: 105473

replace an OpA with a widened OpB, it is possible to get new uses of OpA due to CSE
when recursively updating nodes.  Since OpA has been processed, the new uses are
not examined again.  The patch checks if this occurred and it it did, updates the
new uses of OpA to use OpB.

llvm-svn: 105453

Check that all the instructions are in the same basic block, that the
EXTRACT_SUBREGs write to the same subregs that are being extracted, and that
the source and destination registers are in the same regclass.  Some of
these constraints can be relaxed with a bit more work.  Jakob suggested
that the loop that checks for subregs when NewSubIdx != 0 should use the
"nodbg" iterator, so I made that change here, too.

llvm-svn: 105437

llvm-svn: 105435

needs to demand the high bits because it's asserting that they're zero.

llvm-svn: 105406

llvm-svn: 105399

registers it defines then interfere with an existing preg live range.

For instance, if we had something like these machine instructions:

BB#0
  ... = imul ... EFLAGS<imp-def,dead>
  test ..., EFLAGS<imp-def>
  jcc BB#2 EFLAGS<imp-use>

BB#1
  ... ; fallthrough to BB#2

BB#2
  ... ; No code that defines EFLAGS
  jcc ... EFLAGS<imp-use>

Machine sink will come along, see that imul implicitly defines EFLAGS, but
because it's "dead", it assumes that it can move imul into BB#2. But when it
does, imul's "dead" imp-def of EFLAGS is raised from the dead (a zombie) and
messes up the condition code for the jump (and pretty much anything else which
relies upon it being correct).

The solution is to know which pregs are live going into a basic block. However,
that information isn't calculated at this point. Nor does the LiveVariables pass
take into account non-allocatable physical registers. In lieu of this, we do a
*very* conservative pass through the basic block to determine if a preg is live
coming out of it.

llvm-svn: 105387

llvm-svn: 105379

expansion is the same as that used by LegalizeDAG.

The resulting code sucks in terms of performance/codesize on x86-32 for a
64-bit operation; I haven't looked into whether different expansions might be
better in general.

llvm-svn: 105378

This affects both llvm-gcc and clang.

llvm-svn: 105372

spills and reloads.

This means that a partial define of a register causes a reload so the other
parts of the register are preserved.

The reload can be prevented by adding an <imp-def> operand for the full
register. This is already done by the coalescer and live interval analysis where
relevant.

llvm-svn: 105369

register updates.

These operands tell the spiller that the other parts of the partially defined
register are don't-care, and a reload is not necessary.

llvm-svn: 105361

llvm-svn: 105359

instruction defines subregisters.

Any existing subreg indices on the original instruction are preserved or
composed with the new subreg index.

Also substitute multiple operands mentioning the original register by using the
new MachineInstr::substituteRegister() function. This is necessary because there
will soon be <imp-def> operands added to non read-modify-write partial
definitions. This instruction:

  %reg1234:foo = FLAP %reg1234<imp-def>

will reMaterialize(%reg3333, bar) like this:

  %reg3333:bar-foo = FLAP %reg333:bar<imp-def>

Finally, replace the TargetRegisterInfo pointer argument with a reference to
indicate that it cannot be NULL.

llvm-svn: 105358

llvm-svn: 105344

llvm-svn: 105340

and tidy up the comment describing it.

llvm-svn: 105339

Use local small vector.

llvm-svn: 105332

for debug information.

llvm-svn: 105324

backends and removes the virtual declaration. With that out of the way
I should be able to cleanup one backend at a time.

llvm-svn: 105321

llvm-svn: 105308

checked and it is safe to proceed with the changes.

llvm-svn: 105304

llvm-svn: 105300

The comment about ordering of subreg indices is no longer true.
This exposed a bug in the new substVirtReg method that is also fixed.

llvm-svn: 105294

llvm-svn: 105292

Radar 7927666.

llvm-svn: 105285

llvm-svn: 105283

llvm-svn: 105282