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Cranelift: Add(and modify) simplification rules #13850

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9 changes: 9 additions & 0 deletions cranelift/codegen/src/opts/arithmetic.isle
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Expand Up @@ -568,3 +568,12 @@

;; (-X) * C = X * (-C)
(rule (simplify (imul (fits_in_64 ty) (ineg ty x) (iconst ty y))) (imul ty x (iconst ty (imm64_neg ty y))))

;; -(~x) --> x + 1
(rule (simplify (ineg ty (bnot ty x))) (iadd ty x (iconst_u ty 1)))

;; ~(-x) --> x - 1.
(rule (simplify (bnot ty (ineg ty x))) (isub ty x (iconst_u ty 1)))

;; -1 - x --> ~x
(rule (simplify (isub ty (iconst_s ty -1) x)) (bnot ty x))
12 changes: 10 additions & 2 deletions cranelift/codegen/src/opts/bitops.isle
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Expand Up @@ -14,9 +14,17 @@
(iconst_u ty 0)))
(subsume x))

;; Create an all-zero bit pattern for integer, float, and vector types.

@myunbin myunbin Jul 10, 2026

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Add an all-zero helper for float and vector types.

(decl rec all_zero (Type) Value)
(rule 0 (all_zero (ty_int ty)) (iconst_u ty 0))
(rule 1 (all_zero $F32) (f32const $F32 (f32_from_uint 0)))
(rule 2 (all_zero $F64) (f64const $F64 (f64_from_uint 0)))
(rule 3 (all_zero (ty_vec64 ty)) (splat ty (all_zero (lane_type ty))))
(rule 4 (all_zero (ty_vec128 ty)) (splat ty (all_zero (lane_type ty))))
Comment on lines +22 to +23

@fitzgen fitzgen Jul 10, 2026

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Is it more efficient to load zeros by splatting than via loads from the constant pool?

It seems like we don't have any terms in the mid-end's prelude for working with ir::Constants, but they would be easy to add if necessary.

But if splatting is expected to be more efficient, then we should add a comment to that effect here.


;; x ^ x == 0.
(rule (simplify (bxor (ty_int ty) x x))
(subsume (iconst_u ty 0)))
(rule (simplify (bxor ty x x))
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fitzgen marked this conversation as resolved.
(subsume (all_zero ty)))

;; x ^ not(x) == not(x) ^ x == x | not(x) == not(x) | x == -1.
;; This identity also holds for non-integer types, vectors, and wider types.
Expand Down
3 changes: 3 additions & 0 deletions cranelift/codegen/src/opts/extends.isle
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Expand Up @@ -93,3 +93,6 @@
;; Try to transform an `iconcat` into an i128 into either an sextend or uextend
(rule (simplify (iconcat $I128 x (iconst_u _ 0))) (uextend $I128 x))
(rule (simplify (iconcat $I128 x (sshr _ x (iconst_u _ 63)))) (sextend $I128 x))

;; Select narrowest type
(rule (simplify (ireduce ty (ireduce cty x))) (ireduce ty x))
26 changes: 16 additions & 10 deletions cranelift/codegen/src/opts/icmp.isle
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Expand Up @@ -2,16 +2,16 @@

;; `x == x` is always true for integers; `x != x` is false. Strict
;; inequalities are false, and loose inequalities are true.
(rule (simplify (eq (ty_int ty) x x)) (subsume (iconst_u ty 1)))
(rule (simplify (ne (ty_int ty) x x)) (subsume (iconst_u ty 0)))
(rule (simplify (ugt (ty_int ty) x x)) (subsume (iconst_u ty 0)))
(rule (simplify (uge (ty_int ty) x x)) (subsume (iconst_u ty 1)))
(rule (simplify (sgt (ty_int ty) x x)) (subsume (iconst_u ty 0)))
(rule (simplify (sge (ty_int ty) x x)) (subsume (iconst_u ty 1)))
(rule (simplify (ult (ty_int ty) x x)) (subsume (iconst_u ty 0)))
(rule (simplify (ule (ty_int ty) x x)) (subsume (iconst_u ty 1)))
(rule (simplify (slt (ty_int ty) x x)) (subsume (iconst_u ty 0)))
(rule (simplify (sle (ty_int ty) x x)) (subsume (iconst_u ty 1)))
(rule (simplify (eq ty x x)) (subsume (cmp_true ty)))
(rule (simplify (ne ty x x)) (subsume (iconst_u ty 0)))
(rule (simplify (ugt ty x x)) (subsume (iconst_u ty 0)))
(rule (simplify (uge ty x x)) (subsume (cmp_true ty)))
(rule (simplify (sgt ty x x)) (subsume (iconst_u ty 0)))
(rule (simplify (sge ty x x)) (subsume (cmp_true ty)))
(rule (simplify (ult ty x x)) (subsume (iconst_u ty 0)))
(rule (simplify (ule ty x x)) (subsume (cmp_true ty)))
(rule (simplify (slt ty x x)) (subsume (iconst_u ty 0)))
(rule (simplify (sle ty x x)) (subsume (cmp_true ty)))

;; For integers, adding the same thing on both sides of an equality check
;; (or an inequality check) doesn't change the result.
Expand Down Expand Up @@ -474,3 +474,9 @@

(rule (simplify_skeleton (brif (ireduce _ (clz x_ty x)) _ _))
(replace_branch_cond (sge $I8 x (iconst_u x_ty 0))))

;; ~x == x --> 0
(rule (simplify (eq ty (bnot cty x) x)) (subsume (iconst_u ty 0)))

;; ~x != x --> 1
(rule (simplify (ne ty (bnot cty x) x)) (subsume (cmp_true ty)))
12 changes: 12 additions & 0 deletions cranelift/codegen/src/opts/shifts.isle
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Expand Up @@ -315,3 +315,15 @@
(rule (simplify (iadd ty (ishl ty x z) (ishl ty y z))) (ishl ty (iadd ty x y) z))

(rule (simplify (ushr ty (band ty (ishl ty x y) z) y)) (band ty x (ushr ty z y)))

;; Zero remains zero for any shift or rotate amount.
(rule (simplify (ishl ty (iconst_u ty 0) x)) (subsume (iconst_u ty 0)))
(rule (simplify (ushr ty (iconst_u ty 0) x)) (subsume (iconst_u ty 0)))
(rule (simplify (sshr ty (iconst_u ty 0) x)) (subsume (iconst_u ty 0)))
(rule (simplify (rotl ty (iconst_u ty 0) x)) (subsume (iconst_u ty 0)))
(rule (simplify (rotr ty (iconst_u ty 0) x)) (subsume (iconst_u ty 0)))

;; All ones remain all ones for arithmetic right shifts or rotates.
(rule (simplify (sshr ty (iconst_s ty -1) x)) (subsume (iconst_s ty -1)))
(rule (simplify (rotl ty (iconst_s ty -1) x)) (subsume (iconst_s ty -1)))
(rule (simplify (rotr ty (iconst_s ty -1) x)) (subsume (iconst_s ty -1)))
4 changes: 2 additions & 2 deletions cranelift/filetests/filetests/egraph/arithmetic-precise.clif
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Expand Up @@ -247,8 +247,8 @@ block0(v0: i32x4, v1: i32x4):
; const0 = 0xffffffffffffffffffffffffffffffff
;
; block0(v0: i32x4, v1: i32x4):
; v9 = icmp eq v0, v0
; return v9
; v7 = vconst.i32x4 const0
; return v7 ; v7 = const0
; }

;; (x - y) != x --> y != 0
Expand Down
21 changes: 21 additions & 0 deletions cranelift/filetests/filetests/egraph/arithmetic.clif
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Expand Up @@ -219,6 +219,17 @@ block0(v0: i32):
; check: v6 = ineg v0
; check: return v6

function %ineg_bnot_to_iadd_one(i32) -> i32 {
block0(v0: i32):
v1 = bnot v0
v2 = ineg v1
return v2
}

; check: v3 = iconst.i32 1
; check: v4 = iadd v0, v3 ; v3 = 1
; check: return v4

function %byte_sub_smax_twice(i8) -> i8 {
block0(v0: i8):
v1 = iconst.i8 127
Expand Down Expand Up @@ -464,3 +475,13 @@ block0(v0: i64):
; check: v6 = iadd v4, v5
; check: return v6
}

;; -1 - x --> ~x
function %isub_minus_one_lhs_to_bnot(i32) -> i32 {
block0(v0: i32):
v1 = iconst.i32 -1
v2 = isub v1, v0
return v2
; check: v12 = bnot v0
; check: return v12
}
74 changes: 74 additions & 0 deletions cranelift/filetests/filetests/egraph/bitops.clif
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Expand Up @@ -138,6 +138,54 @@ block0(v1: i64):
; check: v5 = bnot v1
; check: return v5

function %bxor_x_x_f32(f32) -> f32 {
block0(v0: f32):
v1 = bxor v0, v0
return v1
}

; check: v2 = f32const 0.0
; check: return v2

function %bxor_x_x_f64(f64) -> f64 {
block0(v0: f64):
v1 = bxor v0, v0
return v1
}

; check: v2 = f64const 0.0
; check: return v2

function %vector_bxor_x_x_f32x4(f32x4) -> f32x4 {
block0(v0: f32x4):
v1 = bxor v0, v0
return v1
}

; check: const0 = 0x00000000000000000000000000000000
; check: v4 = vconst.f32x4 const0
; check: return v4

function %vector_bxor_x_x_f64x2(f64x2) -> f64x2 {
block0(v0: f64x2):
v1 = bxor v0, v0
return v1
}

; check: const0 = 0x00000000000000000000000000000000
; check: v4 = vconst.f64x2 const0
; check: return v4

function %vector_bxor_x_x_f32x2(f32x2) -> f32x2 {
block0(v0: f32x2):
v1 = bxor v0, v0
return v1
}

; check: f32const 0.0
; check: splat.f32x2
; check: return

function %vector_bxor_x_bnot_x(i32x4) -> i32x4 {
block0(v0: i32x4):
v1 = bnot v0
Expand All @@ -160,6 +208,17 @@ block0(v0: i32x4):
; check: v5 = vconst.i32x4 const0
; check: return v5

function %vector_bxor_bnot_x_bnot_x(i32x4) -> i32x4 {
block0(v0: i32x4):
v1 = bnot v0
v2 = bxor v1, v1
return v2
}

; check: const0 = 0x00000000000000000000000000000000
; check: v5 = vconst.i32x4 const0
; check: return v5

function %vector_bor_x_bnot_x(i32x4) -> i32x4 {
block0(v0: i32x4):
v1 = bnot v0
Expand Down Expand Up @@ -803,6 +862,21 @@ block0(v0: i32, v1: i32):
; return v5
; }

;; (bnot ty (ineg ty x)) -> (isub ty x (iconst_u ty 1))
function %test_bnot_ineg_to_isub_one(i32) -> i32 fast {
block0(v0: i32):
v1 = ineg v0
v2 = bnot v1
return v2
}

; function %test_bnot_ineg_to_isub_one(i32) -> i32 fast {
; block0(v0: i32):
; v3 = iconst.i32 1
; v4 = isub v0, v3
; return v4
; }

;; (bor ty (bxor ty x z) (bor ty y x)) -> (bor ty (bor ty y x) z)
function %test_bor_bxor_bor(i32, i32, i32) -> i32 fast {
block0(v0: i32, v1: i32, v2: i32):
Expand Down
10 changes: 10 additions & 0 deletions cranelift/filetests/filetests/egraph/extends.clif
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Expand Up @@ -134,6 +134,16 @@ block0(v1: i16):
; check: v4 = uextend.i32 v1
; check: return v4

function %nested_ireduce(i64) -> i8 {
block0(v1: i64):
v2 = ireduce.i32 v1
v3 = ireduce.i8 v2
return v3
}

; check: v4 = ireduce.i8 v1
; check: return v4

function %sextend_then_slt_zero(i8) -> i8 {
block0(v0: i8):
v1 = sextend.i16 v0
Expand Down
10 changes: 6 additions & 4 deletions cranelift/filetests/filetests/egraph/i128-opts.clif
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Expand Up @@ -74,16 +74,18 @@ function %eq_self_v128(i8x16) -> i8x16 {
block0(v0: i8x16):
v1 = icmp eq v0, v0
return v1
; check: v1 = icmp eq v0, v0
; check: return v1
; check: const0 = 0xffffffffffffffffffffffffffffffff
; check: v4 = vconst.i8x16 const0
; check: return v4 ; v4 = const0
}

function %ne_self_v128(i8x16) -> i8x16 {
block0(v0: i8x16):
v1 = icmp ne v0, v0
return v1
; check: v1 = icmp ne v0, v0
; check: return v1
; check: const0 = 0x00000000000000000000000000000000
; check: v4 = vconst.i8x16 const0
; check: return v4 ; v4 = const0
}

function %bor_extended_constants_i128() -> i128 {
Expand Down
28 changes: 28 additions & 0 deletions cranelift/filetests/filetests/egraph/icmp.clif
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Expand Up @@ -202,6 +202,34 @@ block0(v0: i32, v1: i32):
; return v5
; }

;; `~x == x` to false.
function %simplify_icmp_eq_bnot_x_x(i32) -> i8 fast {
block0(v0: i32):
v1 = bnot v0
v2 = icmp eq v1, v0
return v2
}

; function %simplify_icmp_eq_bnot_x_x(i32) -> i8 fast {
; block0(v0: i32):
; v3 = iconst.i8 0
; return v3 ; v3 = 0
; }

;; `~x != x` to true.
function %simplify_icmp_ne_bnot_x_x(i32) -> i8 fast {
block0(v0: i32):
v1 = bnot v0
v2 = icmp ne v1, v0
return v2
}

; function %simplify_icmp_ne_bnot_x_x(i32) -> i8 fast {
; block0(v0: i32):
; v3 = iconst.i8 1
; return v3 ; v3 = 1
; }

function %issue_10929_no_crash_on_icmp_vectors() -> i32x4 {
const0 = 0x40ad3fb47cb16076c8cb1fdd8189d40f

Expand Down
63 changes: 63 additions & 0 deletions cranelift/filetests/filetests/egraph/shifts.clif
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Expand Up @@ -606,3 +606,66 @@ block0(v0: i64):
v2 = ishl v0, v1
return v2
}
function %ishl_zero_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 0
v2 = ishl v1, v0
return v2
; check: return v1
}
function %ushr_zero_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 0
v2 = ushr v1, v0
return v2
; check: return v1
}
function %rotl_zero_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 0
v2 = rotl v1, v0
return v2
; check: return v1
}
function %rotr_zero_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 0
v2 = rotr v1, v0
return v2
; check: return v1
}
function %rotl_const_multiple_of_64(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 128
v2 = rotl v0, v1
return v2
; check: return v0
}
function %sshr_all_ones_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 -1
v2 = sshr v1, v0
return v2
; check: return v1
}
function %rotl_all_ones_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 -1
v2 = rotl v1, v0
return v2
; check: return v1
}
function %rotr_all_ones_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 -1
v2 = rotr v1, v0
return v2
; check: return v1
}
function %sshr_zero_left_operand(i64) -> i64 {
block0(v0: i64):
v1 = iconst.i64 0
v2 = sshr v1, v0
return v2
; check: return v1
}
12 changes: 12 additions & 0 deletions cranelift/filetests/filetests/runtests/arithmetic.clif
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Expand Up @@ -1065,3 +1065,15 @@ block0(v0: i64):
; run: %fold_bnot_iadd_neg_const_i64_rt(7) == -1
; run: %fold_bnot_iadd_neg_const_i64_rt(-1) == 7
; run: %fold_bnot_iadd_neg_const_i64_rt(0x80000000_00000000) == 0x80000000_00000006

function %fold_isub_minus_one_lhs_to_bnot_i32_rt(i32) -> i32 fast {
block0(v0: i32):
v1 = iconst.i32 -1
v2 = isub v1, v0
return v2
}

; run: %fold_isub_minus_one_lhs_to_bnot_i32_rt(0) == -1
; run: %fold_isub_minus_one_lhs_to_bnot_i32_rt(1) == -2
; run: %fold_isub_minus_one_lhs_to_bnot_i32_rt(-1) == 0
; run: %fold_isub_minus_one_lhs_to_bnot_i32_rt(0x7fffffff) == 0x80000000
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