Commit Graph

421 Commits

Author SHA1 Message Date
Juergen Ributzka
5273295751 [FastISel][AArch64] Don't fold the sign-/zero-extend from i1 into the compare.
This fixes a bug I introduced in a previous commit (r216033). Sign-/Zero-
extension from i1 cannot be folded into the ADDS/SUBS instructions. Instead both
operands have to be sign-/zero-extended with separate instructions.

Related to <rdar://problem/17913111>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216073 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-20 16:34:15 +00:00
Jiangning Liu
e04455d72b Optimize ZERO_EXTEND and SIGN_EXTEND in both SelectionDAG Builder and type
legalization stage. With those two optimizations, fewer signed/zero extension
instructions can be inserted, and then we can expose more opportunities to
Machine CSE pass in back-end.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216066 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-20 12:05:15 +00:00
Yi Kong
40f9d11ccc ARM: Fix codegen for rbit intrinsic
LLVM generates illegal `rbit r0, #352` instruction for rbit intrinsic.
According to ARM ARM, rbit only takes register as argument, not immediate.
The correct instruction should be rbit <Rd>, <Rm>.

The bug was originally introduced in r211057.

Differential Revision: http://reviews.llvm.org/D4980

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216064 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-20 10:40:20 +00:00
Juergen Ributzka
3ef392c4e2 [FastISel][AArch64] Use the proper FMOV instruction to materialize a +0.0.
Use FMOVWSr/FMOVXDr instead of FMOVSr/FMOVDr, which have the proper register
class to be used with the zero register. This makes the MachineInstruction
verifier happy again.

This is related to <rdar://problem/18027157>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216040 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-20 01:10:36 +00:00
Juergen Ributzka
ae9a7964ef [FastISel][AArch64] Factor out ADDS/SUBS instruction emission and add support for extensions and shift folding.
Factor out the ADDS/SUBS instruction emission code into helper functions and
make the helper functions more clever to support most of the different ADDS/SUBS
instructions the architecture support. This includes better immedediate support,
shift folding, and sign-/zero-extend folding.

This fixes <rdar://problem/17913111>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216033 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 22:29:55 +00:00
Juergen Ributzka
1d58f989d4 [FastISel][AArch64] Extend floating-point materialization test.
This adds the missing test that I promised for r215753 to test the
materialization of the floating-point value +0.0.

Related to <rdar://problem/18027157>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216019 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 20:35:07 +00:00
Juergen Ributzka
06bb1ca1e0 Reapply [FastISel][AArch64] Add support for more addressing modes (r215597).
Note: This was originally reverted to track down a buildbot error. Reapply
without any modifications.

Original commit message:
FastISel didn't take much advantage of the different addressing modes available
to it on AArch64. This commit allows the ComputeAddress method to recognize more
addressing modes that allows shifts and sign-/zero-extensions to be folded into
the memory operation itself.

For Example:
  lsl x1, x1, #3     --> ldr x0, [x0, x1, lsl #3]
  ldr x0, [x0, x1]

  sxtw x1, w1
  lsl x1, x1, #3     --> ldr x0, [x0, x1, sxtw #3]
  ldr x0, [x0, x1]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216013 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 19:44:17 +00:00
Juergen Ributzka
78f686d37c Reapply [FastISel][AArch64] Make use of the zero register when possible (r215591).
Note: This was originally reverted to track down a buildbot error. Reapply
without any modifications.

Original commit message:
This change materializes now the value "0" from the zero register.
The zero register can be folded by several instruction, so no
materialization is need at all.

Fixes <rdar://problem/17924413>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216009 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 19:44:02 +00:00
Juergen Ributzka
8841fb5f25 [FastISel][AArch64] Fix a few BuildMI callsites where the result register was added as an operand register.
This fixes a few BuildMI callsites where the result register was added by
using addReg, which is per default a use and therefore an operand register.

Also use the zero register as result register when emitting a compare
instruction (SUBS with unused result register).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215997 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-19 17:41:53 +00:00
Oliver Stannard
eb922109f9 Teach the AArch64 backend to handle f16
This allows the AArch64 backend to handle fadd, fsub, fmul and fdiv
operations on f16 (half-precision) types by promoting to f32.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215891 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-18 14:22:39 +00:00
Oliver Stannard
802d420792 [ARM,AArch64] Do not tail-call to an externally-defined function with weak linkage
Externally-defined functions with weak linkage should not be
tail-called on ARM or AArch64, as the AAELF spec requires normal calls
to undefined weak functions to be replaced with a NOP or jump to the
next instruction. The behaviour of branch instructions in this
situation (as used for tail calls) is implementation-defined, so we
cannot rely on the linker replacing the tail call with a return.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215890 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-18 12:42:15 +00:00
Amara Emerson
cef3ad6720 [AArch64] Narrow arguments passed in wrong position on the stack in
big-endian mode.

Patch by Asiri Rathnayake.

Differential Revision: http://reviews.llvm.org/D4922

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215716 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-15 14:29:57 +00:00
Juergen Ributzka
6398a7f5fd Revert several FastISel commits to track down a buildbot error.
This reverts:
r215595 "[FastISel][X86] Add large code model support for materializing floating-point constants."
r215594 "[FastISel][X86] Use XOR to materialize the "0" value."
r215593 "[FastISel][X86] Emit more efficient instructions for integer constant materialization."
r215591 "[FastISel][AArch64] Make use of the zero register when possible."
r215588 "[FastISel] Let the target decide first if it wants to materialize a constant."
r215582 "[FastISel][AArch64] Cleanup constant materialization code. NFCI."

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215673 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-14 19:56:28 +00:00
Juergen Ributzka
14bc045838 Revert "[FastISel][AArch64] Add support for more addressing modes."
This reverts commits r215597, because it might have broken the build bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215659 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-14 17:10:54 +00:00
Akira Hatanaka
d0ddfb0896 [AArch64, fast-isel] Fall back to SelectionDAG to select tail calls.
Certain functions such as objc_autoreleaseReturnValue have to be called as
tail-calls even at -O0. Since normal fast-isel doesn't emit calls as tail calls,
we have to fall back to SelectionDAG to select calls that are marked as tail.

<rdar://problem/17991614>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215600 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-13 23:23:58 +00:00
Juergen Ributzka
8c9a0319bb [FastISel][AArch64] Add support for more addressing modes.
FastISel didn't take much advantage of the different addressing modes available
to it on AArch64. This commit allows the ComputeAddress method to recognize more
addressing modes that allows shifts and sign-/zero-extensions to be folded into
the memory operation itself.

For Example:
  lsl x1, x1, #3     --> ldr x0, [x0, x1, lsl #3]
  ldr x0, [x0, x1]

  sxtw x1, w1
  lsl x1, x1, #3     --> ldr x0, [x0, x1, sxtw #3]
  ldr x0, [x0, x1]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215597 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-13 22:53:29 +00:00
Juergen Ributzka
dc408e8069 [FastISel][AArch64] Make use of the zero register when possible.
This change materializes now the value "0" from the zero register.
The zero register can be folded by several instruction, so no
materialization is need at all.

Fixes <rdar://problem/17924413>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215591 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-13 22:13:14 +00:00
Gerolf Hoflehner
392f7d970c [MachineCombiner] Fix for ICE bug 20598
The combiner ignored DBG nodes when checking
the uses of a virtual register.

It combined a sequence like
   %vreg1 = madd %vreg2, %vreg3,...
   DBG_VALUE (%vreg1 ...)
   %vreg4 = add %vreg1,...
to
  %vreg4 = madd %vreg2, %vreg3

leaving behind a dangling DBG_VALUE with
a definition. This triggered an assertion
in the MachineTraceMetrics.cpp module.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215431 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-12 07:54:12 +00:00
Quentin Colombet
7f4f923aa5 [AArch64] Fix registerAllocator assigns same register for base and wback in
pre/post-index load and store.

Patch by Steven Wu <stevenwu@apple.com>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215390 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-11 21:39:53 +00:00
Jiangning Liu
0679d2d0a4 In Machine CSE pass, the source register of a COPY machine instruction can
be propagated to all its users, and this propagation could increase the 
probability of finding common subexpressions. If the COPY has only one user,
the COPY itself can be removed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215344 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-11 05:17:19 +00:00
Jiangning Liu
3b85f30319 [AArch64] Fix a type conversion bug for anlyzing compare.
The bug can cause spec2006/483.xalancbmk failure.

Patched by David Xu.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215206 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-08 14:19:29 +00:00
James Molloy
3a106a2813 [AArch64] Add an FP load balancing pass for Cortex-A57
For best-case performance on Cortex-A57, we should try to use a balanced mix of odd and even D-registers when performing a critical sequence of independent, non-quadword FP/ASIMD floating-point multiply or multiply-accumulate operations.

This pass attempts to detect situations where the register allocation may adversely affect this load balancing and to change the registers used so as to better utilize the CPU.

Ideally we'd just take each multiply or multiply-accumulate in turn and allocate it alternating even or odd registers. However, multiply-accumulates are most efficiently performed in the same functional unit as their accumulation operand. Therefore this pass tries to find maximal sequences ("Chains") of multiply-accumulates linked via their accumulation operand, and assign them all the same "color" (oddness/evenness).

This optimization affects S-register and D-register floating point multiplies and FMADD/FMAs, as well as vector (floating point only) muls and FMADD/FMA. Q register instructions (and 128-bit vector instructions) are not affected.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215199 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-08 12:33:21 +00:00
Tim Northover
bbdf1e0432 AArch64: stop trying to take control of all UnknownArch triples.
This short-circuited our error reporting for incorrectly specified
target triples (you'd get AArch64 code instead).

Should fix PR20567.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215191 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-08 08:27:44 +00:00
Akira Hatanaka
43f6ce9289 [stack protector] Look through bitcasts to get global variable
__stack_chk_guard.

Handle the case where the pointer operand of the load instruction that loads the
stack guard is not a global variable but instead a bitcast.

%StackGuard = load i8** bitcast (i64** @__stack_chk_guard to i8**)
call void @llvm.stackprotector(i8* %StackGuard, i8** %StackGuardSlot)

Original test case provided by Ana Pazos.

This fixes PR20558.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215167 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 23:08:24 +00:00
Gerolf Hoflehner
e4fa341dde MachineCombiner Pass for selecting faster instruction sequence on AArch64
Re-commit of r214832,r21469 with a work-around that
avoids the previous problem with gcc build compilers

The work-around is to use SmallVector instead of ArrayRef
of basic blocks in preservesResourceLen()/MachineCombiner.cpp



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215151 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 21:40:58 +00:00
James Molloy
e0243fb42d [AArch64] Add a testcase for r214957.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214965 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-06 13:31:32 +00:00
Yi Kong
68b3d680f2 AArch64: Add support for instruction prefetch intrinsic
Instruction prefetch is not implemented for AArch64, it is incorrectly
translated into data prefetch instruction.

Differential Revision: http://reviews.llvm.org/D4777


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214860 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 12:46:47 +00:00
Juergen Ributzka
eee659a076 [FastISel][AArch64] Implement the FastLowerArguments hook.
This implements basic argument lowering for AArch64 in FastISel. It only
handles a small subset of the C calling convention. It supports simple
arguments that can be passed in GPR and FPR registers.

This should cover most of the trivial cases without falling back to
SelectionDAG.

This fixes <rdar://problem/17890986>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214846 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 05:43:48 +00:00
Kevin Qin
6739735812 Revert "r214832 - MachineCombiner Pass for selecting faster instruction"
It broke compiling of most Benchmark and internal test, as clang got
clashed by segmentation fault or assertion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214845 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 05:43:47 +00:00
Juergen Ributzka
7e9c0bc511 [FastISel][AArch64] Don't perform sign-/zero-extension for function arguments that have already been sign-/zero-extended.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214844 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 05:43:44 +00:00
Gerolf Hoflehner
c2328d552c MachineCombiner Pass for selecting faster instruction
sequence on AArch64

Re-commit of r214669 without changes to test cases
LLVM::CodeGen/AArch64/arm64-neon-mul-div.ll and
LLVM:: CodeGen/AArch64/dp-3source.ll
This resolves the reported compfails of the original commit.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214832 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-05 01:16:13 +00:00
Juergen Ributzka
2c68cde701 [FastISel][AArch64] Fix shift lowering for i8 and i16 value types.
This fix changes the parameters #r and #s that are passed to the UBFM/SBFM
instruction to get the zero/sign-extension for free.

The original problem was that the shift left would use the 32-bit shift even for
i8/i16 value types, which could leave the upper bits set with "garbage" values.

The arithmetic shift right on the other side would use the wrong MSB as sign-bit
to determine what bits to shift into the value.

This fixes <rdar://problem/17907720>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214788 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-04 21:49:51 +00:00
Chad Rosier
82c93451f3 [AArch64] Extend the number of scalar instructions supported in the AdvSIMD
scalar integer instruction pass.

This is a patch I had lying around from a few months ago.  The pass is
currently disabled by default, so nothing to interesting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214779 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-04 21:20:25 +00:00
Kevin Qin
534100b31e Revert "r214669 - MachineCombiner Pass for selecting faster instruction"
This commit broke "make check" for several hours, so get it reverted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214697 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-04 05:10:33 +00:00
Gerolf Hoflehner
48e1bd7287 MachineCombiner Pass for selecting faster instruction
sequence -  AArch64 target support

 This patch turns off madd/msub generation in the DAGCombiner and generates
 them in the MachineCombiner instead. It replaces the original code sequence
 with the combined sequence when it is beneficial to do so.

 When there is no machine model support it always generates the madd/msub
 instruction. This is true also when the objective is to optimize for code
 size: when the combined sequence is shorter is always chosen and does not
 get evaluated.

 When there is a machine model the combined instruction sequence
 is evaluated for critical path and resource length using machine
 trace metrics and the original code sequence is replaced when it is
 determined to be faster.

 rdar://16319955



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214669 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-03 22:03:40 +00:00
James Molloy
14d596a382 Update test to use a more modern AArch64 triple, as requested by Renato.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214637 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-02 17:15:11 +00:00
James Molloy
e411c38de9 [AArch64] Teach DAGCombiner that converting two consecutive loads into a vector load is not a good transform when paired loads are available.
The combiner was creating Q-register loads and stores, which then had to be spilled because there are no callee-save Q registers!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214634 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-02 14:51:24 +00:00
Juergen Ributzka
8d3bf10dd3 [FastISel][AArch64] Fold offset into the memory operation.
Fold simple offsets into the memory operation:
  add x0, x0, #8
  ldr x0, [x0]
-->
  ldr x0, [x0, #8]

Fixes <rdar://problem/17887945>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214545 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 19:40:16 +00:00
Juergen Ributzka
3d253a3f80 [FastISel][AArch64] Add branch weights.
Add branch weights to branch instructions, so that the following passes can
optimize based on it (i.e. basic block ordering).

Fixes <rdar://problem/17887137>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214537 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 18:39:24 +00:00
Chad Rosier
b4cded4926 [AArch64] Fix test from r214518 in an attempt to appease buildbots.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214521 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 15:30:41 +00:00
Chad Rosier
4175e2f597 [AArch64] Generate tbz/tbnz when comparing against zero.
The tbz/tbnz checks the sign bit to convert

op w1, w1, w10
cmp w1, #0
b.lt .LBB0_0

to

op w1, w1, w10
tbnz w1, #31, .LBB0_0

Differential Revision: http://reviews.llvm.org/D4440

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214518 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 14:48:56 +00:00
Juergen Ributzka
74ac16386b [FastISel][AArch64] Fix the immediate versions of the {s|u}{add|sub}.with.overflow intrinsics.
ADDS and SUBS cannot encode negative immediates or immediates larger than 12bit.
This fix checks if the immediate version can be used under this constraints and
if we can convert ADDS to SUBS or vice versa to support negative immediates.

Also update the test cases to test the immediate versions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214470 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-01 01:25:55 +00:00
Juergen Ributzka
95ec2761f3 [FastISel][AArch64] Add basic bitcast support for conversion between float and int.
Fixes <rdar://problem/17867078>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214389 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-31 06:25:37 +00:00
Juergen Ributzka
a60ed423a6 [FastISel][AArch64] Add sqrt intrinsic support.
Fixes <rdar://problem/17867067>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214388 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-31 06:25:33 +00:00
Juergen Ributzka
e482ebc147 [FastISel][AArch64] Update and enable patchpoint and stackmap intrinsic tests for FastISel.
This commit updates the existing SelectionDAG tests for the stackmap and patchpoint
intrinsics and enables FastISel testing. It also splits up the tests into separate
files, due to different codegen between SelectionDAG and FastISel.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214382 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-31 04:10:43 +00:00
Juergen Ributzka
e3a75015d7 [FastISel][AArch64] Add MachO large code model support for function calls.
Currently the large code model for MachO uses the GOT to make function calls.
Emit the required adrp and ldr instructions to load the address from the GOT.

Related to <rdar://problem/17733076>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214381 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-31 04:10:40 +00:00
Juergen Ributzka
cb99212bc1 [FastISel][AArch64] Add select folding support for the XALU intrinsics.
This improves the code generation for the XALU intrinsics when the
condition is feeding a select instruction.

This also updates and enables the XALU unit tests for FastISel.

This fixes <rdar://problem/17831117>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214350 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-30 22:04:37 +00:00
Juergen Ributzka
b0dba10fa6 [FastISel][AArch64] Add support for shift-immediate.
Currently the shift-immediate versions are not supported by tblgen and
hopefully this can be later removed, once the required support has been
added to tblgen.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214345 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-30 22:04:22 +00:00
Jiangning Liu
a3b8caf8a7 Implement AArch64 TTI interface isAsCheapAsAMove.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214159 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-29 02:09:26 +00:00
Tim Northover
54a7f7f9e0 AArch64: fix conversion of 'J' inline asm constraints.
'J' represents a negative number suitable for an add/sub alias
instruction, but while preparing it to become an int64_t we were
mangling the sign extension. So "i32 -1" became 0xffffffffLL, for
example.

Should fix one half of PR20456.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214052 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-27 07:10:29 +00:00