2044242 - Improve ma_cmp_set with Imm32

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P1)

Description

[André Bargull [:anba]]

ma_cmp_set calls to ma_cmp to use shared code for more conditions, but this approach requires performing an additional xori to negate the result.

For example:

function f(x) {
  return x >= 100000;
}

Is compiled to:

lui       t4, 0x18
addiw     t4, t4, 1696
slt       t1, t0, t4
xori      t1, t1, 0x1

But can instead be compiled to:

lui       t4, 0x18
addiw     t4, t4, 1695
slt       t1, t4, t0

In addition to that, ma_cmp_set with an ImmWord operand should also support negative Imm32 values. For example:

function f(i64) {
  return i64[0] <= -10;
}

Is currently compiled to:

li        t4, -10
slt       t0, t4, t1
xori      t0, t0, 0x1

Instead of the expected:

slti      t0, t1, -9

Comment 1

[André Bargull [:anba]]

Attachment: Bug 2044242 - Part 1: Remove unused ma_cmp with three register operands. r=jandem!

Comment 2

[André Bargull [:anba]]

Attachment: Bug 2044242 - Part 2: Inline ma_cmp into ma_cmp_set and improve it. r=jandem!

And improve it to require no more than three instructions.

For example:

function f(x) {
  return x >= 100000;
}

Was compiled to:

lui       t4, 0x18
addiw     t4, t4, 1696
slt       t1, t0, t4
xori      t1, t1, 0x1

And is now compiled to:

lui       t4, 0x18
addiw     t4, t4, 1695
slt       t1, t4, t0

Comment 3

[André Bargull [:anba]]

Attachment: Bug 2044242 - Part 3: Allow negative int32 for ma_cmp_set with Imm32 operand. r=jandem!

This restriction was copied mips64/loong64, but I don't see any obvious issues
why riscv64 needs to have the same restriction.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/e9e2d87020cf
https://hg.mozilla.org/integration/autoland/rev/3e98db21cbcc
Part 1: Remove unused ma_cmp with three register operands. r=jandem
https://github.com/mozilla-firefox/firefox/commit/2d903319b833
https://hg.mozilla.org/integration/autoland/rev/af1d3d7e0c74
Part 2: Inline ma_cmp into ma_cmp_set and improve it. r=jandem
https://github.com/mozilla-firefox/firefox/commit/a1b73ded5a79
https://hg.mozilla.org/integration/autoland/rev/b4c2a7b52618
Part 3: Allow negative int32 for ma_cmp_set with Imm32 operand. r=jandem

Comment 5

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/3e98db21cbcc
https://hg.mozilla.org/mozilla-central/rev/af1d3d7e0c74
https://hg.mozilla.org/mozilla-central/rev/b4c2a7b52618