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Add optimization from x < 0 || x > POSITIVE_CONST to unsigned(x) > POSITIVE_CONST #6999

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Add optimization from x < 0 || x > POSITIVE_CONST to unsigned(x) > POSITIVE_CONST #6999

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defe0ac
Add optimization from `x < 0 || x > POSITIVE_CONST` to `x > POSITIVE_…
i582 Oct 11, 2024
54280b6
Check equivalence for `x`
i582 Oct 11, 2024
31afc0d
Fix review issues
i582 Oct 15, 2024
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19 changes: 19 additions & 0 deletions src/passes/OptimizeInstructions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -395,6 +395,25 @@ struct OptimizeInstructions
return replaceCurrent(un);
}
}
{
// x < 0 || x > POSITIVE_CONST ==> x > POSITIVE_CONST (unsigned
// comparison)
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Suggested change
// x < 0 || x > POSITIVE_CONST ==> x > POSITIVE_CONST (unsigned
// comparison)
// x < 0 || x > POSITIVE_CONST ==> unsigned(x) > POSITIVE_CONST

(this is the convention we have elsewhere in the file to indicate an unsigned comparison)

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Done

Binary* bin;
Expression *x_left, *x_right;
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Suggested change
Expression *x_left, *x_right;
Expression *xLeft, *xRight;

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Done

Const* y;
if (matches(curr,
binary(&bin,
OrInt32,
binary(LtSInt32, pure(&x_left), i32(0)),
binary(GtSInt32, pure(&x_right), constant(&y)))) &&
y->type == Type::i32 && y->value.geti32() > 0 &&
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Suggested change
y->type == Type::i32 && y->value.geti32() > 0 &&
y->value.geti32() > 0 &&

The type must be i32 because the operation is GtSInt32.

ExpressionAnalyzer::equal(x_left, x_right)) {
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Rather than using pure + ::equal, see areConsecutiveInputsEqualAndFoldable (they are consecutive aside from constants (which are not an issue), we need them to be equal, and we want to fold them together).

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Done

bin->op = GtUInt32;
bin->left = x_left;
bin->right = y;
return;
}
}
{
// x <<>> (C & (31 | 63)) ==> x <<>> C'
// x <<>> (y & (31 | 63)) ==> x <<>> y
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168 changes: 168 additions & 0 deletions test/lit/passes/optimize-instructions-cmps.wast
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@@ -0,0 +1,168 @@
;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
;; RUN: wasm-opt %s --optimize-instructions -S -o - | filecheck %s

;; Tests for "x < 0 || x > POSITIVE_CONST ==> x > POSITIVE_CONST (unsigned comparison)" optimization

(module
;; CHECK: (global $g (mut i32) (i32.const 0))
(global $g (mut i32) (i32.const 0))

;; CHECK: (func $cmp (param $0 i32) (result i32)
;; CHECK-NEXT: (i32.gt_u
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 255)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp (param $0 i32) (result i32)
(i32.or
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Please add comments in the tests, like here, "we can optimize this to a single i32.gt_u".

(i32.lt_s
(local.get $0)
(i32.const 0)
)
(i32.gt_s
(local.get $0)
(i32.const 255)
)
)
)

;; CHECK: (func $cmp2 (param $0 i32) (result i32)
;; CHECK-NEXT: (i32.or
;; CHECK-NEXT: (i32.lt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.gt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const -255)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp2 (param $0 i32) (result i32)
(i32.or
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The comment on this one could be "we cannot optimize here because the second constant is negative".

(i32.lt_s
(local.get $0)
(i32.const 0)
)
(i32.gt_s
(local.get $0)
(i32.const -255) ;; negative number
)
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Please add a testcase where both constants are 0.

)
)

;; CHECK: (func $cmp3 (param $0 i32) (result i32)
;; CHECK-NEXT: (i32.or
;; CHECK-NEXT: (i32.lt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 10)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.gt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 255)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp3 (param $0 i32) (result i32)
(i32.or
(i32.lt_s
(local.get $0)
(i32.const 10) ;; note this
)
(i32.gt_s
(local.get $0)
(i32.const 255)
)
)
)

;; CHECK: (func $set_global_and_return (param $x i32) (result i32)
;; CHECK-NEXT: (global.set $g
;; CHECK-NEXT: (local.get $x)
;; CHECK-NEXT: )
;; CHECK-NEXT: (local.get $x)
;; CHECK-NEXT: )
(func $set_global_and_return (param $x i32) (result i32)
(global.set $g (local.get $x)) ;; side-effect
(local.get $x)
)

;; CHECK: (func $cmp4 (result i32)
;; CHECK-NEXT: (i32.or
;; CHECK-NEXT: (i32.lt_s
;; CHECK-NEXT: (call $set_global_and_return
;; CHECK-NEXT: (i32.const 10)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.gt_s
;; CHECK-NEXT: (call $set_global_and_return
;; CHECK-NEXT: (i32.const 10)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 255)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp4 (result i32)
(i32.or
(i32.lt_s
(call $set_global_and_return (i32.const 10)) ;; x with side-effect
(i32.const 0)
)
(i32.gt_s
(call $set_global_and_return (i32.const 10))
(i32.const 255)
)
)
)

;; CHECK: (func $cmp5 (param $0 i32) (param $1 i32) (result i32)
;; CHECK-NEXT: (i32.or
;; CHECK-NEXT: (i32.lt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.gt_s
;; CHECK-NEXT: (local.get $1)
;; CHECK-NEXT: (i32.const 255)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp5 (param $0 i32) (param $1 i32) (result i32)
(i32.or
(i32.lt_s
(local.get $0)
(i32.const 0)
)
(i32.gt_s
(local.get $1) ;; note this
(i32.const 255)
)
)
)

;; CHECK: (func $cmp6 (param $0 i32) (param $1 i32) (result i32)
;; CHECK-NEXT: (i32.or
;; CHECK-NEXT: (i32.lt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.gt_s
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: (local.get $1)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $cmp6 (param $0 i32) (param $1 i32) (result i32)
(i32.or
(i32.lt_s
(local.get $0)
(i32.const 0)
)
(i32.gt_s
(local.get $0)
(local.get $1) ;; non-constant
)
)
)
)
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