Commit Graph

111 Commits

Author SHA1 Message Date
Alex Bradbury 32b77383ec [SelectionDAG] Support promotion of the FPOWI integer operand
For targets where i32 is not a legal type (e.g. 64-bit RISC-V),
LegalizeIntegerTypes must promote the integer operand of ISD::FPOWI. As this
is a signed value, this should be sign-extended.

This patch enables all tests in test/CodeGen/RISCVfloat-intrinsics.ll for
RV64, as prior to this patch that file couldn't be compiled for RV64 due to an
assertion when performing codegen for fpowi.

Differential Revision: https://reviews.llvm.org/D54574

llvm-svn: 352832
2019-02-01 03:46:28 +00:00
Alex Bradbury d834d8301d [RISCV] Add RV64F codegen support
This requires a little extra work due tothe fact i32 is not a legal type. When
call lowering happens post-legalisation (e.g. when an intrinsic was inserted
during legalisation). A bitcast from f32 to i32 can't be introduced. This is
similar to the challenges with RV32D. To handle this, we introduce
target-specific DAG nodes that perform bitcast+anyext for f32->i64 and
trunc+bitcast for i64->f32.

Differential Revision: https://reviews.llvm.org/D53235

llvm-svn: 352807
2019-01-31 22:48:38 +00:00
Alex Bradbury 0092df0669 [RISCV] Add target DAG combine for bitcast fabs/fneg on RV32FD
DAGCombiner::visitBITCAST will perform:
 fold (bitconvert (fneg x)) -> (xor (bitconvert x), signbit)
 fold (bitconvert (fabs x)) -> (and (bitconvert x), (not signbit))

As shown in double-bitmanip-dagcombines.ll, this can be advantageous. But
RV32FD doesn't use bitcast directly (as i64 isn't a legal type), and instead
uses RISCVISD::SplitF64. This patch adds an equivalent DAG combine for
SplitF64.

llvm-svn: 352247
2019-01-25 21:55:48 +00:00
Alex Bradbury d760910d3d [RISCV] Add another potential combine to {double,float}-bitmanip-dagcombines.ll
(fcopysign a, (fneg b)) will be expanded to bitwise operations by
DAGTypeLegalizer::SoftenFloatRes_FCOPYSIGN if the floating point type isn't
legal. Arguably it might be worth doing a combine even if it is legal.

llvm-svn: 352240
2019-01-25 21:06:47 +00:00
Ana Pazos 05a6064385 Reapply: [RISCV] Set isAsCheapAsAMove for ADDI, ORI, XORI, LUI
This reapplies commit r352010 with RISC-V test fixes.

llvm-svn: 352237
2019-01-25 20:22:49 +00:00
Alex Bradbury c67515d542 [RISCV][NFC] s/f32/f64 in double-arith.ll
The intrinsic names erroneously used the .f32 variant. As the return and
argument types were still double the intrinsics calls worked properly.

llvm-svn: 352211
2019-01-25 16:04:04 +00:00
Alex Bradbury 38c4ec31cb [RISCV] Add tests to demonstrate bitcasted fneg/fabs dagcombines
This target-independent code won't trigger for cases such as RV32FD where
custom SelectionDAG nodes are generated. These new tests demonstrate such
cases. Additionally, float-arith.ll was updated so that fneg.s, fsgnjn.s, and
fabs.s selection patterns are actually exercised.

llvm-svn: 352199
2019-01-25 14:33:08 +00:00
Alex Bradbury 456d3798d6 [RISCV] Custom-legalise i32 SDIV/UDIV/UREM on RV64M
Follow the same custom legalisation strategy as used in D57085 for
variable-length shifts (see that patch summary for more discussion). Although
we may lose out on some late-stage DAG combines, I think this custom
legalisation strategy is ultimately easier to reason about.

There are some codegen changes in rv64m-exhaustive-w-insts.ll but they are all
neutral in terms of the number of instructions.

Differential Revision: https://reviews.llvm.org/D57096

llvm-svn: 352171
2019-01-25 05:11:34 +00:00
Alex Bradbury 299d690a50 [RISCV] Custom-legalise 32-bit variable shifts on RV64
The previous DAG combiner-based approach had an issue with infinite loops
between the target-dependent and target-independent combiner logic (see
PR40333). Although this was worked around in rL351806, the combiner-based
approach is still potentially brittle and can fail to select the 32-bit shift
variant when profitable to do so, as demonstrated in the pr40333.ll test case.

This patch instead introduces target-specific SelectionDAG nodes for
SHLW/SRLW/SRAW and custom-lowers variable i32 shifts to them. pr40333.ll is a
good example of how this approach can improve codegen.

This adds DAG combine that does SimplifyDemandedBits on the operands (only
lower 32-bits of first operand and lower 5 bits of second operand are read).
This seems better than implementing SimplifyDemandedBitsForTargetNode as there
is no guarantee that would be called (and it's not for e.g. the anyext return
test cases). Also implements ComputeNumSignBitsForTargetNode.

There are codegen changes in atomic-rmw.ll and atomic-cmpxchg.ll but the new
instruction sequences are semantically equivalent.

Differential Revision: https://reviews.llvm.org/D57085

llvm-svn: 352169
2019-01-25 05:04:00 +00:00
Alex Bradbury cd26560e46 [RISCV] Quick fix for PR40333
Avoid the infinite loop caused by the target DAG combine converting ANYEXT to
SIGNEXT and the target-independent DAG combine logic converting back to
ANYEXT. Do this by not adding the new node to the worklist.

Committing directly as this definitely doesn't make the problem any worse, and
I intend to follow-up with a patch that avoids this custom combiner logic
altogether and just lowers the i32 operations to a target-specific
SelectionDAG node. This should be easier to reason about and improve codegen
quality in some cases (though may miss out on some later DAG combines).

llvm-svn: 351806
2019-01-22 12:11:53 +00:00
Alex Bradbury 07f1c62371 [RISCV] Add codegen support for RV64A
In order to support codegen RV64A, this patch:
* Introduces masked atomics intrinsics for atomicrmw operations and cmpxchg
  that use the i64 type. These are ultimately lowered to masked operations
  using lr.w/sc.w, but we need to use these alternate intrinsics for RV64
  because i32 is not legal
* Modifies RISCVExpandPseudoInsts.cpp to handle PseudoAtomicLoadNand64 and
  PseudoCmpXchg64
* Modifies the AtomicExpandPass hooks in RISCVTargetLowering to sext/trunc as
  needed for RV64 and to select the i64 intrinsic IDs when necessary
* Adds appropriate patterns to RISCVInstrInfoA.td
* Updates test/CodeGen/RISCV/atomic-*.ll to show RV64A support

This ends up being a fairly mechanical change, as the logic for RV32A is
effectively reused.

Differential Revision: https://reviews.llvm.org/D53233

llvm-svn: 351422
2019-01-17 10:04:39 +00:00
Francis Visoiu Mistrih b7cef81fd3 Replace "no-frame-pointer-*" function attributes with "frame-pointer"
Part of the effort to refactoring frame pointer code generation. We used
to use two function attributes "no-frame-pointer-elim" and
"no-frame-pointer-elim-non-leaf" to represent three kinds of frame
pointer usage: (all) frames use frame pointer, (non-leaf) frames use
frame pointer, (none) frame use frame pointer. This CL makes the idea
explicit by using only one enum function attribute "frame-pointer"

Option "-frame-pointer=" replaces "-disable-fp-elim" for tools such as
llc.

"no-frame-pointer-elim" and "no-frame-pointer-elim-non-leaf" are still
supported for easy migration to "frame-pointer".

tests are mostly updated with

// replace command line args ‘-disable-fp-elim=false’ with ‘-frame-pointer=none’
grep -iIrnl '\-disable-fp-elim=false' * | xargs sed -i '' -e "s/-disable-fp-elim=false/-frame-pointer=none/g"

// replace command line args ‘-disable-fp-elim’ with ‘-frame-pointer=all’
grep -iIrnl '\-disable-fp-elim' * | xargs sed -i '' -e "s/-disable-fp-elim/-frame-pointer=all/g"

Patch by Yuanfang Chen (tabloid.adroit)!

Differential Revision: https://reviews.llvm.org/D56351

llvm-svn: 351049
2019-01-14 10:55:55 +00:00
Alex Bradbury 61aa940074 [RISCV] Introduce codegen patterns for RV64M-only instructions
As discussed on llvm-dev
<http://lists.llvm.org/pipermail/llvm-dev/2018-December/128497.html>, we have
to be careful when trying to select the *w RV64M instructions. i32 is not a
legal type for RV64 in the RISC-V backend, so operations have been promoted by
the time they reach instruction selection. Information about whether the
operation was originally a 32-bit operations has been lost, and it's easy to
write incorrect patterns.

Similarly to the variable 32-bit shifts, a DAG combine on ANY_EXTEND will
produce a SIGN_EXTEND if this is likely to result in sdiv/udiv/urem being
selected (and so save instructions to sext/zext the input operands).

Differential Revision: https://reviews.llvm.org/D53230

llvm-svn: 350993
2019-01-12 07:43:06 +00:00
Alex Bradbury d05eae7a7b [RISCV] Add patterns for RV64I SLLW/SRLW/SRAW instructions
This restores support for selecting the SLLW/SRLW/SRAW instructions, which was
removed in rL348067 as the previous patterns made some unsafe assumptions.
Also see the related llvm-dev discussion
<http://lists.llvm.org/pipermail/llvm-dev/2018-December/128497.html>

Ultimately I didn't introduce a custom SelectionDAG node, but instead added a
DAG combine that inserts an AssertZext i5 on the shift amount for an i32
variable-length shift and also added an ANY_EXTEND DAG-combine which will
instead produce a SIGN_EXTEND for an i32 variable-length shift, increasing the
opportunity to safely select SLLW/SRLW/SRAW.

There are obviously different ways of addressing this (a number discussed in
the llvm-dev thread), so I'd welcome further feedback and comments.

Note that there are now some cases in
test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll where sraw/srlw/sllw is
selected even though sra/srl/sll could be used without any extra instructions.
Given both are semantically equivalent, there doesn't seem a good reason to
prefer one vs the other. Given that would require more logic to still select
sra/srl/sll in those cases, I've left it preferring the *w variants.

Differential Revision: https://reviews.llvm.org/D56264

llvm-svn: 350992
2019-01-12 07:32:31 +00:00
Alex Bradbury eea0b07028 [RISCV][NFC] Add CHECK lines for atomic operations on RV64I
As or RV32I, we include these for completeness. Committing now to make it
easier to review the RV64A patch.

llvm-svn: 350962
2019-01-11 19:46:48 +00:00
Alex Bradbury 919f5fb8ca [RISCV] Add support for the various RISC-V FMA instruction variants
Adds support for the various RISC-V FMA instructions (fmadd, fmsub, fnmsub, fnmadd).

The criteria for choosing whether a fused add or subtract is used, as well as
whether the product is negated or not, is whether some of the arguments to the
llvm.fma.* intrinsic are negated or not. In the tests, extraneous fadd
instructions were added to avoid the negation being performed using a xor
trick, which prevented the proper FMA forms from being selected and thus
tested.

The FMA instruction patterns might seem incorrect (e.g., fnmadd: -rs1 * rs2 -
rs3), but they should be correct. The misleading names were inherited from
MIPS, where the negation happens after computing the sum.

The llvm.fmuladd.* intrinsics still do not generate RISC-V FMA instructions,
as that depends on TargetLowering::isFMAFasterthanFMulAndFAdd.

Some comments in the test files about what type of instructions are there
tested were updated, to better reflect the current content of those test
files.

Differential Revision: https://reviews.llvm.org/D54205
Patch by Luís Marques.

llvm-svn: 349023
2018-12-13 10:49:05 +00:00
Alex Bradbury 757d296222 [RISCV] Remove RV64I SLLW/SRLW/SRAW patterns and add new test cases
As noted by Eli Friedman <https://reviews.llvm.org/D52977?id=168629#1315291>, 
the RV64I shift patterns for SLLW/SRLW/SRAW make some incorrect assumptions. 
SRAW assumed that (sext_inreg foo, i32) could only be produced when 
sign-extended an i32. However, it can be produced by input such as:

define i64 @tricky_ashr(i64 %a, i64 %b) {
  %1 = shl i64 %a, 32
  %2 = ashr i64 %1, 32
  %3 = ashr i64 %2, %b
  ret i64 %3
}

It's important not to select sraw in the above case, because sraw only uses 
bits lower 5 bits from the shift, while a shift of 32-63 would be valid.

Similarly, the patterns for srlw assumed (and foo, 0xffffffff) would only be 
produced when zero-extending a value that was originally i32 in LLVM IR. This
is obviously incorrect.

This patch removes the SLLW/SRLW/SRAW shift patterns for the time being and 
adds test cases that would demonstrate a miscompile if the incorrect patterns 
were re-added.

llvm-svn: 348067
2018-12-01 05:00:00 +00:00
Alex Bradbury fca95cfee9 [SelectionDAG] Support result type promotion for FLT_ROUNDS_
For targets where i32 is not a legal type (e.g. 64-bit RISC-V), 
LegalizeIntegerTypes must promote the result of ISD::FLT_ROUNDS_.

Differential Revision: https://reviews.llvm.org/D53820

llvm-svn: 347986
2018-11-30 13:18:33 +00:00
Alex Bradbury bd24c7b045 [SelectionDAG] Support promotion of PREFETCH operands
For targets where i32 is not a legal type (e.g. 64-bit RISC-V), 
LegalizeIntegerTypes must promote the operands of ISD::PREFETCH.

Differential Revision: https://reviews.llvm.org/D53281

llvm-svn: 347980
2018-11-30 10:06:31 +00:00
Alex Bradbury 36e0fd1d39 [SelectionDAG] Support promotion of FRAMEADDR/RETURNADDR operands
For targets where i32 is not a legal type (e.g. 64-bit RISC-V), 
LegalizeIntegerTypes must promote the operand.

Differential Revision: https://reviews.llvm.org/D53279

llvm-svn: 347978
2018-11-30 10:02:06 +00:00
Alex Bradbury e0e62e97df [TargetLowering][RISCV] Introduce isSExtCheaperThanZExt hook and implement for RISC-V
DAGTypeLegalizer::PromoteSetCCOperands currently prefers to zero-extend 
operands when it is able to do so. For some targets this is more expensive 
than a sign-extension, which is also a valid choice. Introduce the 
isSExtCheaperThanZExt hook and use it in the new SExtOrZExtPromotedInteger 
helper. On RISC-V, we prefer sign-extension for FromTy == MVT::i32 and ToTy == 
MVT::i64, as it can be performed using a single instruction.

Differential Revision: https://reviews.llvm.org/D52978

llvm-svn: 347977
2018-11-30 09:56:54 +00:00
Alex Bradbury bc96a98ed0 [RISCV] Introduce codegen patterns for instructions introduced in RV64I
As discussed in the RFC 
<http://lists.llvm.org/pipermail/llvm-dev/2018-October/126690.html>, 64-bit 
RISC-V has i64 as the only legal integer type.  This patch introduces patterns 
to support codegen of the new instructions 
introduced in RV64I: addiw, addiw, subw, sllw, slliw, srlw, srliw, sraw, 
sraiw, ld, sd.

Custom selection code is needed for srliw as SimplifyDemandedBits will remove 
lower bits from the mask, meaning the obvious pattern won't work:

def : Pat<(sext_inreg (srl (and GPR:$rs1, 0xffffffff), uimm5:$shamt), i32),
          (SRLIW GPR:$rs1, uimm5:$shamt)>;
This is sufficient to compile and execute all of the GCC torture suite for 
RV64I other than those files using frameaddr or returnaddr intrinsics 
(LegalizeDAG doesn't know how to promote the operands - a future patch 
addresses this).

When promoting i32 sltu/sltiu operands, it would be more efficient to use 
sign-extension rather than zero-extension for RV64. A future patch adds a hook 
to allow this.

Differential Revision: https://reviews.llvm.org/D52977

llvm-svn: 347973
2018-11-30 09:38:44 +00:00
Alex Bradbury 66d9a752b9 [RISCV] Implement codegen for cmpxchg on RV32IA
Utilise a similar ('late') lowering strategy to D47882. The changes to 
AtomicExpandPass allow this strategy to be utilised by other targets which 
implement shouldExpandAtomicCmpXchgInIR.

All cmpxchg are lowered as 'strong' currently and failure ordering is ignored. 
This is conservative but correct.

Differential Revision: https://reviews.llvm.org/D48131

llvm-svn: 347914
2018-11-29 20:43:42 +00:00
Alex Bradbury 2146e8fb1e [RISCV] Constant materialisation for RV64I
This commit introduces support for materialising 64-bit constants for RV64I,
making use of the RISCVMatInt::generateInstSeq helper in order to share logic
for immediate materialisation with the MC layer (where it's used for the li
pseudoinstruction).

test/CodeGen/RISCV/imm.ll is updated to test RV64, and gains new 64-bit
constant tests. It would be preferable if anyext constant returns were sign
rather than zero extended (see PR39092). This patch simply adds an explicit
signext to the returns in imm.ll.

Further optimisations for constant materialisation are possible, most notably
for mask-like values which can be generated my loading -1 and shifting right.
A future patch will standardise on the C++ codepath for immediate selection on
RV32 as well as RV64, and then add further such optimisations to
RISCVMatInt::generateInstSeq in order to benefit both RV32 and RV64 for
codegen and li expansion.

Differential Revision: https://reviews.llvm.org/D52962

llvm-svn: 347042
2018-11-16 10:14:16 +00:00
Alex Bradbury 7727240438 [RISCV] Mark FREM as Expand
Mark the FREM SelectionDAG node as Expand, which is necessary in order to 
support the frem IR instruction on RISC-V. This is expanded into a library 
call. Adds the corresponding test. Previously, this would have triggered an 
assertion at instruction selection time.

Differential Revision: https://reviews.llvm.org/D54159
Patch by Luís Marques.

llvm-svn: 346958
2018-11-15 14:46:11 +00:00
Alex Bradbury 9c03e4cacd [RISCV] Support .option relax and .option norelax
This extends the .option support from D45864 to enable/disable the relax 
feature flag from D44886

During parsing of the relax/norelax directives, the RISCV::FeatureRelax 
feature bits of the SubtargetInfo stored in the AsmParser are updated 
appropriately to reflect whether relaxation is currently enabled in the 
parser. When an instruction is parsed, the parser checks if relaxation is 
currently enabled and if so, gets a handle to the AsmBackend and sets the 
ForceRelocs flag. The AsmBackend uses a combination of the original 
RISCV::FeatureRelax feature bits set by e.g -mattr=+/-relax and the 
ForceRelocs flag to determine whether to emit relocations for symbol and 
branch diffs. Diff relocations should therefore only not be emitted if the 
relax flag was not set on the command line and no instruction was ever parsed 
in a section with relaxation enabled to ensure correct diffs are emitted.

Differential Revision: https://reviews.llvm.org/D46423
Patch by Lewis Revill.

llvm-svn: 346655
2018-11-12 14:25:07 +00:00
Alex Bradbury 1cc2d0b9fb [RISCV] Avoid unnecessary XOR for seteq/setne 0
Differential Revision: https://reviews.llvm.org/D53492

Patch by James Clarke.

llvm-svn: 346497
2018-11-09 14:47:36 +00:00
Alex Bradbury a9da1de5f4 [RISCV] Update test/CodeGen/RISCV/calling-conv.ll after rL346432
The DAGCombiner changes led to a different schedule.

llvm-svn: 346496
2018-11-09 14:35:44 +00:00
Alex Bradbury 52c27785ce [RISCV] Add some missing expansions for floating-point intrinsics
A number of intrinsics, such as llvm.sin.f32, would result in a failure to 
select. This patch adds expansions for the relevant selection DAG nodes, as 
well as exhaustive testing for all f32 and f64 intrinsics.

The codegen for FMA remains a TODO item, pending support for the various 
RISC-V FMA instruction variants.

The llvm.minimum.f32.* and llvm.maximum.* tests are commented-out, pending 
upstream support for target-independent expansion, as discussed in 
http://lists.llvm.org/pipermail/llvm-dev/2018-November/127408.html.

Differential Revision: https://reviews.llvm.org/D54034
Patch by Luís Marques.

llvm-svn: 346034
2018-11-02 19:50:38 +00:00
Alex Bradbury 748d080e62 [RISCV] Eliminate unnecessary masking of promoted shift amounts
SelectionDAGBuilder::visitShift will always zero-extend a shift amount when it
is promoted to the ShiftAmountTy. This results in zero-extension (masking)
which is unnecessary for RISC-V as the shift operations only read the lower 5
or 6 bits (RV32 or RV64).

I initially proposed adding a getExtendForShiftAmount hook so the shift amount
can be any-extended (D52975). @efriedma explained this was unsafe, so I have
instead eliminate the unnecessary and operations at instruction selection time
in a manner similar to X86InstrCompiler.td.

Differential Revision: https://reviews.llvm.org/D53224

llvm-svn: 344432
2018-10-12 23:18:52 +00:00
Alex Bradbury 686ef92141 [RISCV] Re-generate test/CodeGen/RISCV/vararg.ll after r344142
The improved load-store forwarding committed in r344142 broke this test.

llvm-svn: 344238
2018-10-11 11:11:58 +00:00
Alex Bradbury 5af6c1496a [RISCV] Update alu8.ll and alu16.ll test cases
The srli test in alu8.ll was a no-op, as it shifted by 8 bits. Fix this, and 
also change the immediate in alu16.ll as shifted by something other than a 
poewr of 8 is more interesting.

llvm-svn: 343958
2018-10-08 09:08:51 +00:00
Alex Bradbury 47afe5e7c0 [RISCV] Introduce alu8.ll and alu16.ll tests
These track the quality of generated code for simple arithmetic operations
that were legalised from non-native types.

llvm-svn: 343930
2018-10-07 06:53:46 +00:00
Alex Bradbury 90fc100742 [RISCV] Regenerate several tests now enableMultipleCopyHints is enabled by default
r343851 caused codegen changes in several tests. This patch regenerates them.

llvm-svn: 343873
2018-10-05 18:25:55 +00:00
Alex Bradbury a4b7b6dabc [RISCV][NFC] Remove dead CHECK lines from vararg.ll test
The RISCV32 check prefix is no longer used so these lines are dead.

llvm-svn: 343757
2018-10-04 07:35:52 +00:00
Alex Bradbury e96b7c88a3 [RISCV] Bugfix for floats passed on the stack with the ILP32 ABI on RV32F
f32 values passed on the stack would previously cause an assertion in 
unpackFromMemLoc.. This would only trigger in the presence of the F extension 
making f32 a legal type. Otherwise the f32 would be legalized.

This patch fixes that by keeping LocVT=f32 when a float is passed on the 
stack. It also adds test coverage for this case, and tests that also 
demonstrate lw/sw/flw/fsw will be selected when most profitable. i.e. there is 
no unnecessary i32<->f32 conversion in registers.

llvm-svn: 343756
2018-10-04 07:28:49 +00:00
Alex Bradbury efceb59801 [RISCV] Remove RV64 test lines from umulo-128-legalisation-lowering.ll
The generated code is incorrect anyway, and this test adds noise to the 
upcoming set of patches that flesh out RV64 support.

llvm-svn: 343675
2018-10-03 10:59:42 +00:00
Alex Bradbury 21aea51e71 [RISCV] Codegen for i8, i16, and i32 atomicrmw with RV32A
Introduce a new RISCVExpandPseudoInsts pass to expand atomic 
pseudo-instructions after register allocation. This is necessary in order to 
ensure that register spills aren't introduced between LL and SC, thus breaking 
the forward progress guarantee for the operation. AArch64 does something 
similar for CmpXchg (though only at O0), and Mips is moving towards this 
approach (see D31287). See also [this mailing list 
post](http://lists.llvm.org/pipermail/llvm-dev/2016-May/099490.html) from 
James Knight, which summarises the issues with lowering to ll/sc in IR or 
pre-RA.

See the [accompanying RFC 
thread](http://lists.llvm.org/pipermail/llvm-dev/2018-June/123993.html) for an 
overview of the lowering strategy.

Differential Revision: https://reviews.llvm.org/D47882

llvm-svn: 342534
2018-09-19 10:54:22 +00:00
Roger Ferrer Ibanez fe28217048 [RISCV] atomic_store_nn have a different layout to regular store
We cannot directy reuse the patterns of StPat because for some reason the store
DAG node and the atomic_store_nn DAG nodes put the ptr and the value in
different positions. Currently we attempt to store the address to an address
formed by the value.

Differential Revision: https://reviews.llvm.org/D51217

llvm-svn: 340722
2018-08-27 07:08:18 +00:00
Eli Friedman 73e8a784e6 [SelectionDAG] Improve the legalisation lowering of UMULO.
There is no way in the universe, that doing a full-width division in
software will be faster than doing overflowing multiplication in
software in the first place, especially given that this same full-width
multiplication needs to be done anyway.

This patch replaces the previous implementation with a direct lowering
into an overflowing multiplication algorithm based on half-width
operations.

Correctness of the algorithm was verified by exhaustively checking the
output of this algorithm for overflowing multiplication of 16 bit
integers against an obviously correct widening multiplication. Baring
any oversights introduced by porting the algorithm to DAG, confidence in
correctness of this algorithm is extremely high.

Following table shows the change in both t = runtime and s = space. The
change is expressed as a multiplier of original, so anything under 1 is
“better” and anything above 1 is worse.

+-------+-----------+-----------+-------------+-------------+
| Arch  | u64*u64 t | u64*u64 s | u128*u128 t | u128*u128 s |
+-------+-----------+-----------+-------------+-------------+
|   X64 |     -     |     -     |    ~0.5     |    ~0.64    |
|  i686 |   ~0.5    |   ~0.6666 |    ~0.05    |    ~0.9     |
| armv7 |     -     |   ~0.75   |      -      |    ~1.4     |
+-------+-----------+-----------+-------------+-------------+

Performance numbers have been collected by running overflowing
multiplication in a loop under `perf` on two x86_64 (one Intel Haswell,
other AMD Ryzen) based machines. Size numbers have been collected by
looking at the size of function containing an overflowing multiply in
a loop.

All in all, it can be seen that both performance and size has improved
except in the case of armv7 where code size has regressed for 128-bit
multiply. u128*u128 overflowing multiply on 32-bit platforms seem to
benefit from this change a lot, taking only 5% of the time compared to
original algorithm to calculate the same thing.

The final benefit of this change is that LLVM is now capable of lowering
the overflowing unsigned multiply for integers of any bit-width as long
as the target is capable of lowering regular multiplication for the same
bit-width. Previously, 128-bit overflowing multiply was the widest
possible.

Patch by Simonas Kazlauskas!

Differential Revision: https://reviews.llvm.org/D50310

llvm-svn: 339922
2018-08-16 18:39:39 +00:00
Alex Bradbury fdc4647ca3 [RISCV][MC] Don't fold symbol differences if requiresDiffExpressionRelocations is true
When emitting the difference between two symbols, the standard behavior is 
that the difference will be resolved to an absolute value if both of the 
symbols are offsets from the same data fragment. This is undesirable on 
architectures such as RISC-V where relaxation in the linker may cause the 
computed difference to become invalid. This caused an issue when compiling to 
object code, where the size of a function in the debug information was already 
calculated even though it could change as a consequence of relaxation in the 
subsequent linking stage.

This patch inhibits the resolution of symbol differences to absolute values 
where the target's AsmBackend has declared that it does not want these to be 
folded.

Differential Revision: https://reviews.llvm.org/D45773
Patch by Edward Jones.

llvm-svn: 339864
2018-08-16 11:26:37 +00:00
Ana Pazos 2baa767455 [RISCV] Fixed test case failure due to r338047
llvm-svn: 338341
2018-07-31 00:36:28 +00:00
Ana Pazos 2e4106b73d [RISCV] Add support for _interrupt attribute
- Save/restore only registers that are used.
This includes Callee saved registers and Caller saved registers
(arguments and temporaries) for integer and FP registers.
- If there is a call in the interrupt handler, save/restore all
Caller saved registers (arguments and temporaries) and all FP registers.
- Emit special return instructions depending on "interrupt"
attribute type.
Based on initial patch by Zhaoshi Zheng.

Reviewers: asb

Reviewed By: asb

Subscribers: rkruppe, the_o, MartinMosbeck, brucehoult, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang, rogfer01, llvm-commits

Differential Revision: https://reviews.llvm.org/D48411

llvm-svn: 338047
2018-07-26 17:49:43 +00:00
Sameer AbuAsal 9b65ffb097 [RISCV] Add machine function pass to merge base + offset
Summary:
   In r333455 we added a peephole to fix the corner cases that result
   from separating base + offset lowering of global address.The
   peephole didn't handle some of the cases because it only has a basic
   block view instead of a function level view.

   This patch replaces that logic with a machine function pass. In
   addition to handling the original cases it handles uses of the global
   address across blocks in function and folding an offset from LW\SW
   instruction. This pass won't run for OptNone compilation, so there
   will be a negative impact overall vs the old approach at O0.

Reviewers: asb, apazos, mgrang

Reviewed By: asb

Subscribers: MartinMosbeck, brucehoult, the_o, rogfer01, mgorny, rbar, johnrusso, simoncook, niosHD, kito-cheng, shiva0217, zzheng, llvm-commits, edward-jones

Differential Revision: https://reviews.llvm.org/D47857

llvm-svn: 335786
2018-06-27 20:51:42 +00:00
Chandler Carruth e5f1b8e20b [RISC-V] Fix a test case to not include label names as those aren't
stable in non-asserts builds. This fixes a test failure in release
config.

llvm-svn: 335202
2018-06-21 05:42:05 +00:00
Roger Ferrer Ibanez ec03fbe8bb [RISCV] Add tests for overflow intrinsics
This is using the existing codegen so we can see the change once we custom
lower ISD::{U,S}{ADD,SUB}O nodes.

llvm-svn: 335023
2018-06-19 06:45:47 +00:00
Alex Bradbury 96f492d7df [RISCV] Add codegen support for atomic load/stores with RV32A
Fences are inserted according to table A.6 in the current draft of version 2.3
of the RISC-V Instruction Set Manual, which incorporates the memory model
changes and definitions contributed by the RISC-V Memory Consistency Model
task group.

Instruction selection failures will now occur for 8/16/32-bit atomicrmw and 
cmpxchg operations when targeting RV32IA until lowering for these operations 
is added in a follow-on patch.

Differential Revision: https://reviews.llvm.org/D47589

llvm-svn: 334591
2018-06-13 12:04:51 +00:00
Alex Bradbury dc790dd5d0 [RISCV] Codegen support for atomic operations on RV32I
This patch adds lowering for atomic fences and relies on AtomicExpandPass to
lower atomic loads/stores, atomic rmw, and cmpxchg to __atomic_* libcalls.

test/CodeGen/RISCV/atomic-* are modelled on the exhaustive
test/CodeGen/PPC/atomics-regression.ll, and will prove more useful once RV32A
codegen support is introduced.

Fence mappings are taken from table A.6 in the current draft of version 2.3 of
the RISC-V Instruction Set Manual, which incorporates the memory model changes
and definitions contributed by the RISC-V Memory Consistency Model task group.

Differential Revision: https://reviews.llvm.org/D47587

llvm-svn: 334590
2018-06-13 11:58:46 +00:00
Sameer AbuAsal 97684419e8 [RISCV] Add peepholes for Global Address lowering patterns
Summary:
  Base and offset are always separated when a GlobalAddress node is lowered
  (rL332641) as an optimization to reduce instruction count. However, this
  optimization is not profitable if the Global Address ends up being used in only
  instruction.

  This patch adds peephole optimizations that merge an offset of
  an address calculation into the LUI %%hi and ADD %lo of the lowering sequence.

  The peephole handles three patterns:

 1) ADDI (ADDI (LUI %hi(global)) %lo(global)), offset
     --->
      ADDI (LUI %hi(global + offset)) %lo(global + offset).

   This generates:
   lui a0, hi (global + offset)
   add a0, a0, lo (global + offset)

   Instead of

   lui a0, hi (global)
   addi a0, hi (global)
   addi a0, offset

   This pattern is for cases when the offset is small enough to fit in the
   immediate filed of ADDI (less than 12 bits).

 2) ADD ((ADDI (LUI %hi(global)) %lo(global)), (LUI hi_offset))
     --->
      offset = hi_offset << 12
      ADDI (LUI %hi(global + offset)) %lo(global + offset)

   Which generates the ASM:

   lui  a0, hi(global + offset)
   addi a0, lo(global + offset)

   Instead of:

   lui  a0, hi(global)
   addi a0, lo(global)
   lui a1, (offset)
   add a0, a0, a1

   This pattern is for cases when the offset doesn't fit in an immediate field
   of ADDI but the lower 12 bits are all zeros.

 3) ADD ((ADDI (LUI %hi(global)) %lo(global)), (ADDI lo_offset, (LUI hi_offset)))
     --->
        offset = global + offhi20<<12 + offlo12
        ADDI (LUI %hi(global + offset)) %lo(global + offset)

   Which generates the ASM:

   lui  a1, %hi(global + offset)
   addi a1, %lo(global + offset)

   Instead of:

   lui  a0, hi(global)
   addi a0, lo(global)
   lui a1, (offhi20)
   addi a1, (offlo12)
   add a0, a0, a1

   This pattern is for cases when the offset doesn't fit in an immediate field
   of ADDI and both the lower 1 bits and high 20 bits are non zero.

    Reviewers: asb

    Reviewed By: asb

    Subscribers: rbar, johnrusso, simoncook, jordy.potman.lists, apazos,
  niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang

llvm-svn: 333455
2018-05-29 19:34:54 +00:00
Mandeep Singh Grang ddcb95664e [RISCV] Lower the tail pseudoinstruction
This patch lowers the tail pseudoinstruction. This has been modeled after ARM's
tail call opt.

llvm-svn: 333137
2018-05-23 22:44:08 +00:00