llvm-project/llvm/lib/Target/WebAssembly
Benjamin Kramer ef0a45aaa5 [WebAssembly] Unbreak the build.
Not sure why ADL isn't working here.

llvm-svn: 280656
2016-09-05 12:06:47 +00:00
..
Disassembler [WebAssembly] Implement support for custom NaN bit patterns. 2016-02-16 15:14:23 +00:00
InstPrinter [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
MCTargetDesc [WebAssembly] Support CFI for WebAssembly target 2016-08-01 22:25:02 +00:00
TargetInfo Remove autoconf support 2016-01-26 21:29:08 +00:00
CMakeLists.txt [WebAssembly] Refactor WebAssemblyLowerEmscriptenException pass for setjmp/longjmp 2016-08-18 15:27:25 +00:00
LLVMBuild.txt Add asm.js-style setjmp/longjmp handling for wasm 2016-08-31 22:40:34 +00:00
README.txt [WebAssembly] Remove a README.txt entry that is now implemented. 2016-08-02 14:53:44 +00:00
WebAssembly.h [WebAssembly] Refactor WebAssemblyLowerEmscriptenException pass for setjmp/longjmp 2016-08-18 15:27:25 +00:00
WebAssembly.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyArgumentMove.cpp [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyAsmPrinter.cpp [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyCFGStackify.cpp [WebAssembly] Unbreak the build. 2016-09-05 12:06:47 +00:00
WebAssemblyFastISel.cpp [WebAssembly] Check return value of getRegForValue in FastISel 2016-08-04 18:01:52 +00:00
WebAssemblyFixIrreducibleControlFlow.cpp [WebAssembly] Account for implicit operands when computing operand indices. 2016-04-26 01:40:56 +00:00
WebAssemblyFrameLowering.cpp [WebAssembly] Plug MachineMemOperand leaks. 2016-08-12 18:33:50 +00:00
WebAssemblyFrameLowering.h Change eliminateCallFramePseudoInstr() to return an iterator 2016-03-31 18:33:38 +00:00
WebAssemblyISD.def [WebAssembly] Update for spec change from tableswitch to br_table. 2016-03-08 03:18:12 +00:00
WebAssemblyISelDAGToDAG.cpp SDAG: Implement Select instead of SelectImpl in WebAssemblyDAGToDAGISel 2016-05-13 22:44:57 +00:00
WebAssemblyISelLowering.cpp [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyISelLowering.h Pass DebugLoc and SDLoc by const ref. 2016-06-12 15:39:02 +00:00
WebAssemblyInstrAtomics.td
WebAssemblyInstrCall.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyInstrControl.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyInstrConv.td [SelectionDAG] Rename fextend -> fpextend, fround -> fpround, frnd -> fround 2016-08-18 20:08:15 +00:00
WebAssemblyInstrFloat.td [WebAssembly] Update the select instructions' operand orders to match the spec. 2016-02-05 17:14:59 +00:00
WebAssemblyInstrFormats.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyInstrInfo.cpp Rename AnalyzeBranch* to analyzeBranch*. 2016-07-15 14:41:04 +00:00
WebAssemblyInstrInfo.h Rename AnalyzeBranch* to analyzeBranch*. 2016-07-15 14:41:04 +00:00
WebAssemblyInstrInfo.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyInstrInteger.td [WebAssembly] Set ctlz_zero_undef/cttz_zero_undef to Expand so LegalizeDAG will convert them to ctlz/cttz. Remove the now unneccessary isel patterns. NFC 2016-04-23 02:49:25 +00:00
WebAssemblyInstrMemory.td [WebAssembly] Disable folding of GA+reg into load/store constant offsets 2016-08-31 20:27:20 +00:00
WebAssemblyInstrSIMD.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyLowerBrUnless.cpp [WebAssembly] Use eqz to negate a branch conditions. 2016-05-16 18:59:34 +00:00
WebAssemblyLowerEmscriptenEHSjLj.cpp [WebAssembly] Add asm.js-style setjmp/longjmp handling for wasm (reland r280302) 2016-09-01 21:05:15 +00:00
WebAssemblyMCInstLower.cpp [WebAssembly] Make CFG stackification independent of basic-block labels. 2016-01-12 19:14:46 +00:00
WebAssemblyMCInstLower.h [WebAssembly] Define WebAssembly-specific relocation codes. 2016-01-11 23:38:05 +00:00
WebAssemblyMachineFunctionInfo.cpp
WebAssemblyMachineFunctionInfo.h Remove dead function with incredibly broken assert. 2016-06-06 12:10:42 +00:00
WebAssemblyOptimizeLiveIntervals.cpp [WebAssembly] Move register stackification and coloring to a late phase. 2016-05-10 04:24:02 +00:00
WebAssemblyOptimizeReturned.cpp
WebAssemblyPeephole.cpp [WebAssembly] Remove unnecessary subtarget checks in peephole pass 2016-08-02 23:31:56 +00:00
WebAssemblyPrepareForLiveIntervals.cpp [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyRegColoring.cpp [WebAssembly] Rename $discard to $drop in the assembly output. 2016-05-17 23:19:03 +00:00
WebAssemblyRegNumbering.cpp [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyRegStackify.cpp [WebAssembly] Handle debug information and virtual registers without crashing (reland r278967) 2016-08-17 23:42:27 +00:00
WebAssemblyRegisterInfo.cpp MachineFunction: Return reference for getFrameInfo(); NFC 2016-07-28 18:40:00 +00:00
WebAssemblyRegisterInfo.h
WebAssemblyRegisterInfo.td [WebAssembly] Initial SIMD128 support. 2016-08-02 23:16:09 +00:00
WebAssemblyReplacePhysRegs.cpp [WebAssembly] Handle debug information and virtual registers without crashing (reland r278967) 2016-08-17 23:42:27 +00:00
WebAssemblySelectionDAGInfo.cpp
WebAssemblySelectionDAGInfo.h Rename TargetSelectionDAGInfo into SelectionDAGTargetInfo and move it to CodeGen/ 2016-01-27 16:32:26 +00:00
WebAssemblySetP2AlignOperands.cpp [WebAssembly] Limit alignment hints to natural alignment. 2016-04-21 23:59:48 +00:00
WebAssemblyStoreResults.cpp [WebAssembly] Disable the store-results optimization. 2016-08-18 17:51:27 +00:00
WebAssemblySubtarget.cpp [WebAssembly] Disable the MachineScheduler. 2016-05-18 20:19:02 +00:00
WebAssemblySubtarget.h
WebAssemblyTargetMachine.cpp [WebAssembly] Add asm.js-style setjmp/longjmp handling for wasm (reland r280302) 2016-09-01 21:05:15 +00:00
WebAssemblyTargetMachine.h [WebAssembly] Update WebAssembly target for r269988. 2016-05-19 03:00:05 +00:00
WebAssemblyTargetObjectFile.cpp [WebAssembly] Convert WebAssemblyTargetObjectFile to TargetLoweringObjectFileELF 2015-12-17 04:55:44 +00:00
WebAssemblyTargetObjectFile.h [WebAssembly] Convert WebAssemblyTargetObjectFile to TargetLoweringObjectFileELF 2015-12-17 04:55:44 +00:00
WebAssemblyTargetTransformInfo.cpp [WebAssembly] Basic TargetTransformInfo support for SIMD128. 2016-05-23 22:47:07 +00:00
WebAssemblyTargetTransformInfo.h [WebAssembly] Basic TargetTransformInfo support for SIMD128. 2016-05-23 22:47:07 +00:00
known_gcc_test_failures.txt [WebAssembly] Update known test failures 2016-09-02 16:26:24 +00:00

README.txt

//===-- README.txt - Notes for WebAssembly code gen -----------------------===//

This WebAssembly backend is presently in a very early stage of development.
The code should build and not break anything else, but don't expect a lot more
at this point.

For more information on WebAssembly itself, see the design documents:
  * https://github.com/WebAssembly/design/blob/master/README.md

The following documents contain some information on the planned semantics and
binary encoding of WebAssembly itself:
  * https://github.com/WebAssembly/design/blob/master/AstSemantics.md
  * https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md

The backend is built, tested and archived on the following waterfall:
  https://wasm-stat.us

The backend's bringup is done using the GCC torture test suite first since it
doesn't require C library support. Current known failures are in
known_gcc_test_failures.txt, all other tests should pass. The waterfall will
turn red if not. Once most of these pass, further testing will use LLVM's own
test suite. The tests can be run locally using:
  https://github.com/WebAssembly/waterfall/blob/master/src/compile_torture_tests.py

//===---------------------------------------------------------------------===//

Br, br_if, and br_table instructions can support having a value on the
expression stack across the jump (sometimes). We should (a) model this, and
(b) extend the stackifier to utilize it.

//===---------------------------------------------------------------------===//

The min/max operators aren't exactly a<b?a:b because of NaN and negative zero
behavior. The ARM target has the same kind of min/max instructions and has
implemented optimizations for them; we should do similar optimizations for
WebAssembly.

//===---------------------------------------------------------------------===//

AArch64 runs SeparateConstOffsetFromGEPPass, followed by EarlyCSE and LICM.
Would these be useful to run for WebAssembly too? Also, it has an option to
run SimplifyCFG after running the AtomicExpand pass. Would this be useful for
us too?

//===---------------------------------------------------------------------===//

Register stackification uses the EXPR_STACK physical register to impose
ordering dependencies on instructions with stack operands. This is pessimistic;
we should consider alternate ways to model stack dependencies.

//===---------------------------------------------------------------------===//

Lots of things could be done in WebAssemblyTargetTransformInfo.cpp. Similarly,
there are numerous optimization-related hooks that can be overridden in
WebAssemblyTargetLowering.

//===---------------------------------------------------------------------===//

Instead of the OptimizeReturned pass, which should consider preserving the
"returned" attribute through to MachineInstrs and extending the StoreResults
pass to do this optimization on calls too. That would also let the
WebAssemblyPeephole pass clean up dead defs for such calls, as it does for
stores.

//===---------------------------------------------------------------------===//

Consider implementing optimizeSelect, optimizeCompareInstr, optimizeCondBranch,
optimizeLoadInstr, and/or getMachineCombinerPatterns.

//===---------------------------------------------------------------------===//

Find a clean way to fix the problem which leads to the Shrink Wrapping pass
being run after the WebAssembly PEI pass.

//===---------------------------------------------------------------------===//

When setting multiple local variables to the same constant, we currently get
code like this:

    i32.const   $4=, 0
    i32.const   $3=, 0

It could be done with a smaller encoding like this:

    i32.const   $push5=, 0
    tee_local   $push6=, $4=, $pop5
    copy_local  $3=, $pop6

//===---------------------------------------------------------------------===//

WebAssembly registers are implicitly initialized to zero. Explicit zeroing is
therefore often redundant and could be optimized away.

//===---------------------------------------------------------------------===//

Small indices may use smaller encodings than large indices.
WebAssemblyRegColoring and/or WebAssemblyRegRenumbering should sort registers
according to their usage frequency to maximize the usage of smaller encodings.

//===---------------------------------------------------------------------===//

Many cases of irreducible control flow could be transformed more optimally
than via the transform in WebAssemblyFixIrreducibleControlFlow.cpp.

It may also be worthwhile to do transforms before register coloring,
particularly when duplicating code, to allow register coloring to be aware of
the duplication.

//===---------------------------------------------------------------------===//

WebAssemblyRegStackify could use AliasAnalysis to reorder loads and stores more
aggressively.

//===---------------------------------------------------------------------===//

WebAssemblyRegStackify is currently a greedy algorithm. This means that, for
example, a binary operator will stackify with its user before its operands.
However, if moving the binary operator to its user moves it to a place where
its operands can't be moved to, it would be better to leave it in place, or
perhaps move it up, so that it can stackify its operands. A binary operator
has two operands and one result, so in such cases there could be a net win by
prefering the operands.

//===---------------------------------------------------------------------===//

Instruction ordering has a significant influence on register stackification and
coloring. Consider experimenting with the MachineScheduler (enable via
enableMachineScheduler) and determine if it can be configured to schedule
instructions advantageously for this purpose.

//===---------------------------------------------------------------------===//