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Author SHA1 Message Date
Jason Molenda 0d8cd4e2d5 [AArch64InstPrinter] Change printAddSubImm to comment imm value when shifted 
Add a comment when there is a shifted value,
    add x9, x0, #291, lsl #12 ; =1191936
but not when the immediate value is unshifted,
    subs x9, x0, #256 ; =256
when the comment adds nothing additional to the reader.

Differential Revision: https://reviews.llvm.org/D107196
 2021-08-03 02:28:46 -07:00
Simonas Kazlauskas 777a58e05b Support {S,U}REMEqFold before legalization 
This allows these optimisations to apply to e.g. `urem i16` directly
before `urem` is promoted to i32 on architectures where i16 operations
are not intrinsically legal (such as on Aarch64). The legalization then
later can happen more directly and generated code gets a chance to avoid
wasting time on computing results in types wider than necessary, in the end.

Seems like mostly an improvement in terms of results at least as far as x86_64 and aarch64 are concerned, with a few regressions here and there. It also helps in preventing regressions in changes like {D87976}.

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D88785
 2021-04-01 01:35:41 +03:00
Craig Topper 5744502a13 [TargetLowering][RISCV][AArch64][PowerPC] Enable BuildUDIV/BuildSDIV on illegal types before type legalization if we can find a larger legal type that supports MUL. 
If we wait until the type is legalized, we'll lose information
about the orginal type and need to use larger magic constants.
This gets especially bad on RISCV64 where i64 is the only legal
type.

I've limited this to simple scalar types so it only works for
i8/i16/i32 which are most likely to occur. For more odd types
we might want to do a small promotion to a type where MULH is legal
instead.

Unfortunately, this does prevent some urem/srem+seteq matching since
that still require legal types.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D96210
 2021-02-11 09:43:13 -08:00
Roman Lebedev 96cf5c8d47
[Codegen] TargetLowering::prepareUREMEqFold(): `x u% C1 ==/!= C2` (PR35479) 
Summary:
The current lowering is:
```
Name: (X % C1) == C2 -> X * C3 <= C4 || false
Pre: (C2 == 0 || C1 u<= C2) && (C1 u>> countTrailingZeros(C1)) * C3 == 1
%zz = and i8 C3, 0 ; trick alive into making C3 avaliable in precondition
%o0 = urem i8 %x, C1
%r = icmp eq i8 %o0, C2
  =>
%zz = and i8 C3, 0 ; and silence it from complaining about said reg
%C4 = -1 /u C1
%n0 = mul i8 %x, C3
%n1 = lshr i8 %n0, countTrailingZeros(C1) ; rotate right
%n2 = shl i8 %n0, ((8-countTrailingZeros(C1)) %u 8) ; rotate right
%n3 = or i8 %n1, %n2 ; rotate right
%is_tautologically_false = icmp ule i8 C1, C2
%C4_fixed = select i1 %is_tautologically_false, i8 -1, i8 %C4
%res = icmp ule i8 %n3, %C4_fixed
%r = xor i1 %res, %is_tautologically_false
```
https://rise4fun.com/Alive/2xC
https://rise4fun.com/Alive/jpb5

However, we can support non-tautological cases `C1 u> C2` too.
Said handling consists of two parts:
* `C2 u<= (-1 %u C1)`. It just works. We only have to change `(X % C1) == C2` into `((X - C2) % C1) == 0`
```
Name: (X % C1) == C2 -> (X - C2) * C3 <= C4   iff C2 u<= (-1 %u C1)
Pre: (C1 u>> countTrailingZeros(C1)) * C3 == 1 && C2 u<= (-1 %u C1)
%zz = and i8 C3, 0 ; trick alive into making C3 avaliable in precondition
%o0 = urem i8 %x, C1
%r = icmp eq i8 %o0, C2
  =>
%zz = and i8 C3, 0 ; and silence it from complaining about said reg
%C4 = (-1 /u C1)
%n0 = sub i8 %x, C2
%n1 = mul i8 %n0, C3
%n2 = lshr i8 %n1, countTrailingZeros(C1) ; rotate right
%n3 = shl i8 %n1, ((8-countTrailingZeros(C1)) %u 8) ; rotate right
%n4 = or i8 %n2, %n3 ; rotate right
%is_tautologically_false = icmp ule i8 C1, C2
%C4_fixed = select i1 %is_tautologically_false, i8 -1, i8 %C4
%res = icmp ule i8 %n4, %C4_fixed
%r = xor i1 %res, %is_tautologically_false
```
https://rise4fun.com/Alive/m4P
https://rise4fun.com/Alive/SKrx
* `C2 u> (-1 %u C1)`. We also have to change `(X % C1) == C2` into `((X - C2) % C1) == 0`,
  and we have to decrement C4:
```
Name: (X % C1) == C2 -> (X - C2) * C3 <= C4   iff C2 u> (-1 %u C1)
Pre: (C1 u>> countTrailingZeros(C1)) * C3 == 1 && C2 u> (-1 %u C1)
%zz = and i8 C3, 0 ; trick alive into making C3 avaliable in precondition
%o0 = urem i8 %x, C1
%r = icmp eq i8 %o0, C2
  =>
%zz = and i8 C3, 0 ; and silence it from complaining about said reg
%C4 = (-1 /u C1)-1
%n0 = sub i8 %x, C2
%n1 = mul i8 %n0, C3
%n2 = lshr i8 %n1, countTrailingZeros(C1) ; rotate right
%n3 = shl i8 %n1, ((8-countTrailingZeros(C1)) %u 8) ; rotate right
%n4 = or i8 %n2, %n3 ; rotate right
%is_tautologically_false = icmp ule i8 C1, C2
%C4_fixed = select i1 %is_tautologically_false, i8 -1, i8 %C4
%res = icmp ule i8 %n4, %C4_fixed
%r = xor i1 %res, %is_tautologically_false
```
https://rise4fun.com/Alive/d40
https://rise4fun.com/Alive/8cF

I believe this concludes `x u% C1 ==/!= C2` lowering.
In fact, clang is may now be better in this regard than gcc:
as it can be seen from `@t32_6_4` test, we do lower `x % 6 == 4`
via this pattern, while gcc does not: https://godbolt.org/z/XNU2z9
And all the general alive proofs say this is legal.
And manual checking agrees: https://rise4fun.com/Alive/WA2

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=35479 | PR35479 ]].

Reviewers: RKSimon, craig.topper, spatel

Reviewed By: RKSimon

Subscribers: nick, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70053
 2019-11-22 15:22:42 +03:00
Roman Lebedev 7874db75ef
[NFC][Codegen] Add `x u% C1 == C2` with C1 u> C2 non-tautological tests 2019-11-10 19:44:46 +03:00