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mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-22 18:54:02 +01:00
llvm-mirror/lib/Target/SystemZ
Jonas Paulsson be22f38105 [SystemZ] Fix bad instruction name
SLGBR -> SLBGR

Reviewed by Ulrich Weigand

llvm-svn: 257874
2016-01-15 07:12:09 +00:00
..
AsmParser Reduce the size of MCRelaxableFragment. 2015-11-14 06:35:56 +00:00
Disassembler
InstPrinter Remove extra forward declarations and scrub includes for all in tree InstPrinters. NFC 2015-12-25 22:10:01 +00:00
MCTargetDesc Convert a few assert failures into proper errors. 2016-01-13 22:56:57 +00:00
TargetInfo
CMakeLists.txt
LLVMBuild.txt
Makefile
README.txt
SystemZ.h
SystemZ.td
SystemZAsmPrinter.cpp
SystemZAsmPrinter.h
SystemZCallingConv.cpp
SystemZCallingConv.h
SystemZCallingConv.td
SystemZConstantPoolValue.cpp Drop prelink support. 2015-11-17 00:51:23 +00:00
SystemZConstantPoolValue.h Drop prelink support. 2015-11-17 00:51:23 +00:00
SystemZElimCompare.cpp Untabify. 2015-11-02 01:38:12 +00:00
SystemZFrameLowering.cpp [Stack realignment] Handling of aligned allocas. 2015-11-28 11:02:32 +00:00
SystemZFrameLowering.h
SystemZInstrBuilder.h
SystemZInstrFormats.td [SystemZ] Make the CCRegs regclass non-allocatable. 2015-10-29 16:13:55 +00:00
SystemZInstrFP.td [SystemZ] Don't forget the CC def op on LTEBRCompare pseudos 2015-10-26 15:03:32 +00:00
SystemZInstrInfo.cpp [SystemZ] Bugfix: Don't add CC twice to new three-address instruction. 2015-12-04 12:48:51 +00:00
SystemZInstrInfo.h
SystemZInstrInfo.td [SystemZ] Fix bad instruction name 2016-01-15 07:12:09 +00:00
SystemZInstrVector.td
SystemZISelDAGToDAG.cpp
SystemZISelLowering.cpp [SystemZ] Fix assertion failure in adjustSubwordCmp 2015-12-16 18:04:06 +00:00
SystemZISelLowering.h [WinEH] Update exception pointer registers 2015-11-07 01:11:31 +00:00
SystemZLDCleanup.cpp
SystemZLongBranch.cpp
SystemZMachineFunctionInfo.cpp
SystemZMachineFunctionInfo.h
SystemZMCInstLower.cpp
SystemZMCInstLower.h
SystemZOperands.td
SystemZOperators.td
SystemZPatterns.td
SystemZProcessors.td
SystemZRegisterInfo.cpp
SystemZRegisterInfo.h
SystemZRegisterInfo.td [SystemZ] Make the CCRegs regclass non-allocatable. 2015-10-29 16:13:55 +00:00
SystemZSelectionDAGInfo.cpp
SystemZSelectionDAGInfo.h
SystemZShortenInst.cpp [SystemZ] Tie operands in SystemZShorteInst if MI becomes 2-address. 2015-10-26 15:03:07 +00:00
SystemZSubtarget.cpp
SystemZSubtarget.h
SystemZTargetMachine.cpp [PostRA scheduling] Allow a target to do scheduling when it wants post RA. 2015-12-10 09:10:07 +00:00
SystemZTargetMachine.h [PostRA scheduling] Allow a target to do scheduling when it wants post RA. 2015-12-10 09:10:07 +00:00
SystemZTargetTransformInfo.cpp
SystemZTargetTransformInfo.h

//===---------------------------------------------------------------------===//
// Random notes about and ideas for the SystemZ backend.
//===---------------------------------------------------------------------===//

The initial backend is deliberately restricted to z10.  We should add support
for later architectures at some point.

--

SystemZDAGToDAGISel::SelectInlineAsmMemoryOperand() is passed "m" for all
inline asm memory constraints; it doesn't get to see the original constraint.
This means that it must conservatively treat all inline asm constraints
as the most restricted type, "R".

--

If an inline asm ties an i32 "r" result to an i64 input, the input
will be treated as an i32, leaving the upper bits uninitialised.
For example:

define void @f4(i32 *%dst) {
  %val = call i32 asm "blah $0", "=r,0" (i64 103)
  store i32 %val, i32 *%dst
  ret void
}

from CodeGen/SystemZ/asm-09.ll will use LHI rather than LGHI.
to load 103.  This seems to be a general target-independent problem.

--

The tuning of the choice between LOAD ADDRESS (LA) and addition in
SystemZISelDAGToDAG.cpp is suspect.  It should be tweaked based on
performance measurements.

--

There is no scheduling support.

--

We don't use the BRANCH ON INDEX instructions.

--

We might want to use BRANCH ON CONDITION for conditional indirect calls
and conditional returns.

--

We don't use the TEST DATA CLASS instructions.

--

We only use MVC, XC and CLC for constant-length block operations.
We could extend them to variable-length operations too,
using EXECUTE RELATIVE LONG.

MVCIN, MVCLE and CLCLE may be worthwhile too.

--

We don't use CUSE or the TRANSLATE family of instructions for string
operations.  The TRANSLATE ones are probably more difficult to exploit.

--

We don't take full advantage of builtins like fabsl because the calling
conventions require f128s to be returned by invisible reference.

--

ADD LOGICAL WITH SIGNED IMMEDIATE could be useful when we need to
produce a carry.  SUBTRACT LOGICAL IMMEDIATE could be useful when we
need to produce a borrow.  (Note that there are no memory forms of
ADD LOGICAL WITH CARRY and SUBTRACT LOGICAL WITH BORROW, so the high
part of 128-bit memory operations would probably need to be done
via a register.)

--

We don't use the halfword forms of LOAD REVERSED and STORE REVERSED
(LRVH and STRVH).

--

We don't use ICM or STCM.

--

DAGCombiner doesn't yet fold truncations of extended loads.  Functions like:

    unsigned long f (unsigned long x, unsigned short *y)
    {
      return (x << 32) | *y;
    }

therefore end up as:

        sllg    %r2, %r2, 32
        llgh    %r0, 0(%r3)
        lr      %r2, %r0
        br      %r14

but truncating the load would give:

        sllg    %r2, %r2, 32
        lh      %r2, 0(%r3)
        br      %r14

--

Functions like:

define i64 @f1(i64 %a) {
  %and = and i64 %a, 1
  ret i64 %and
}

ought to be implemented as:

        lhi     %r0, 1
        ngr     %r2, %r0
        br      %r14

but two-address optimisations reverse the order of the AND and force:

        lhi     %r0, 1
        ngr     %r0, %r2
        lgr     %r2, %r0
        br      %r14

CodeGen/SystemZ/and-04.ll has several examples of this.

--

Out-of-range displacements are usually handled by loading the full
address into a register.  In many cases it would be better to create
an anchor point instead.  E.g. for:

define void @f4a(i128 *%aptr, i64 %base) {
  %addr = add i64 %base, 524288
  %bptr = inttoptr i64 %addr to i128 *
  %a = load volatile i128 *%aptr
  %b = load i128 *%bptr
  %add = add i128 %a, %b
  store i128 %add, i128 *%aptr
  ret void
}

(from CodeGen/SystemZ/int-add-08.ll) we load %base+524288 and %base+524296
into separate registers, rather than using %base+524288 as a base for both.

--

Dynamic stack allocations round the size to 8 bytes and then allocate
that rounded amount.  It would be simpler to subtract the unrounded
size from the copy of the stack pointer and then align the result.
See CodeGen/SystemZ/alloca-01.ll for an example.

--

If needed, we can support 16-byte atomics using LPQ, STPQ and CSDG.

--

We might want to model all access registers and use them to spill
32-bit values.