// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Optimizations TODO:
// * Use SLTI and SLTIU for comparisons to constants, instead of SLT/SLTU with constants in registers
// * Use the zero register instead of moving 0 into a register.
// * Add rules to avoid generating a temp bool value for (If (SLT[U] ...) ...).
// * Optimize left and right shift by simplifying SLTIU, Neg, and ADD for constants.
// * Arrange for non-trivial Zero and Move lowerings to use aligned loads and stores.
// * Eliminate zero immediate shifts, adds, etc.
// * Avoid using Neq32 for writeBarrier.enabled checks.

// Lowering arithmetic
(Add64 ...) => (ADD ...)
(AddPtr ...) => (ADD ...)
(Add32 ...) => (ADD ...)
(Add16 ...) => (ADD ...)
(Add8 ...) => (ADD ...)
(Add32F ...) => (FADDS ...)
(Add64F ...) => (FADDD ...)

(Sub64 ...) => (SUB ...)
(SubPtr ...) => (SUB ...)
(Sub32 ...) => (SUB ...)
(Sub16 ...) => (SUB ...)
(Sub8 ...) => (SUB ...)
(Sub32F ...) => (FSUBS ...)
(Sub64F ...) => (FSUBD ...)

(Mul64 ...) => (MUL  ...)
(Mul32 ...) => (MULW ...)
(Mul16 x y) => (MULW (SignExt16to32 x) (SignExt16to32 y))
(Mul8 x y)  => (MULW (SignExt8to32 x)  (SignExt8to32 y))
(Mul32F ...) => (FMULS ...)
(Mul64F ...) => (FMULD ...)

(Div32F ...) => (FDIVS ...)
(Div64F ...) => (FDIVD ...)

(Div64 x y [false])  => (DIV x y)
(Div64u ...) => (DIVU ...)
(Div32 x y [false])  => (DIVW x y)
(Div32u ...) => (DIVUW ...)
(Div16 x y [false])  => (DIVW  (SignExt16to32 x) (SignExt16to32 y))
(Div16u x y) => (DIVUW (ZeroExt16to32 x) (ZeroExt16to32 y))
(Div8 x y)   => (DIVW  (SignExt8to32 x)  (SignExt8to32 y))
(Div8u x y)  => (DIVUW (ZeroExt8to32 x)  (ZeroExt8to32 y))

(Hmul64 ...)  => (MULH  ...)
(Hmul64u ...) => (MULHU ...)
(Hmul32 x y)  => (SRAI [32] (MUL  (SignExt32to64 x) (SignExt32to64 y)))
(Hmul32u x y) => (SRLI [32] (MUL  (ZeroExt32to64 x) (ZeroExt32to64 y)))

// (x + y) / 2 => (x / 2) + (y / 2) + (x & y & 1)
(Avg64u <t> x y) => (ADD (ADD <t> (SRLI <t> [1] x) (SRLI <t> [1] y)) (ANDI <t> [1] (AND <t> x y)))

(Mod64 x y [false])  => (REM x y)
(Mod64u ...) => (REMU  ...)
(Mod32 x y [false])  => (REMW x y)
(Mod32u ...) => (REMUW ...)
(Mod16 x y [false])  => (REMW  (SignExt16to32 x) (SignExt16to32 y))
(Mod16u x y) => (REMUW (ZeroExt16to32 x) (ZeroExt16to32 y))
(Mod8 x y)   => (REMW  (SignExt8to32  x) (SignExt8to32  y))
(Mod8u x y)  => (REMUW (ZeroExt8to32  x) (ZeroExt8to32  y))

(And64 ...) => (AND ...)
(And32 ...) => (AND ...)
(And16 ...) => (AND ...)
(And8  ...) => (AND ...)

(Or64 ...) => (OR ...)
(Or32 ...) => (OR ...)
(Or16 ...) => (OR ...)
(Or8  ...) => (OR ...)

(Xor64 ...) => (XOR ...)
(Xor32 ...) => (XOR ...)
(Xor16 ...) => (XOR ...)
(Xor8  ...) => (XOR ...)

(Neg64  ...) => (NEG ...)
(Neg32  ...) => (NEG ...)
(Neg16  ...) => (NEG ...)
(Neg8   ...) => (NEG ...)
(Neg32F ...) => (FNEGS ...)
(Neg64F ...) => (FNEGD ...)

(Com64 ...) => (NOT ...)
(Com32 ...) => (NOT ...)
(Com16 ...) => (NOT ...)
(Com8  ...) => (NOT ...)

(Sqrt ...) => (FSQRTD ...)
(Sqrt32 ...) => (FSQRTS ...)

// Sign and zero extension.

(SignExt8to16  ...) => (MOVBreg ...)
(SignExt8to32  ...) => (MOVBreg ...)
(SignExt8to64  ...) => (MOVBreg ...)
(SignExt16to32 ...) => (MOVHreg ...)
(SignExt16to64 ...) => (MOVHreg ...)
(SignExt32to64 ...) => (MOVWreg ...)

(ZeroExt8to16  ...) => (MOVBUreg ...)
(ZeroExt8to32  ...) => (MOVBUreg ...)
(ZeroExt8to64  ...) => (MOVBUreg ...)
(ZeroExt16to32 ...) => (MOVHUreg ...)
(ZeroExt16to64 ...) => (MOVHUreg ...)
(ZeroExt32to64 ...) => (MOVWUreg ...)

(Cvt32to32F ...) => (FCVTSW ...)
(Cvt32to64F ...) => (FCVTDW ...)
(Cvt64to32F ...) => (FCVTSL ...)
(Cvt64to64F ...) => (FCVTDL ...)

(Cvt32Fto32 ...) => (FCVTWS ...)
(Cvt32Fto64 ...) => (FCVTLS ...)
(Cvt64Fto32 ...) => (FCVTWD ...)
(Cvt64Fto64 ...) => (FCVTLD ...)

(Cvt32Fto64F ...) => (FCVTDS ...)
(Cvt64Fto32F ...) => (FCVTSD ...)

(CvtBoolToUint8 ...) => (Copy ...)

(Round32F ...) => (Copy ...)
(Round64F ...) => (Copy ...)

// From genericOps.go:
// "0 if arg0 == 0, -1 if arg0 > 0, undef if arg0<0"
//
// Like other arches, we compute ~((x-1) >> 63), with arithmetic right shift.
// For positive x, bit 63 of x-1 is always 0, so the result is -1.
// For zero x, bit 63 of x-1 is 1, so the result is 0.
//
(Slicemask <t> x) => (NOT (SRAI <t> [63] (ADDI <t> [-1] x)))

// Truncations
// We ignore the unused high parts of registers, so truncates are just copies.
(Trunc16to8  ...) => (Copy ...)
(Trunc32to8  ...) => (Copy ...)
(Trunc32to16 ...) => (Copy ...)
(Trunc64to8  ...) => (Copy ...)
(Trunc64to16 ...) => (Copy ...)
(Trunc64to32 ...) => (Copy ...)

// Shifts

// SLL only considers the bottom 6 bits of y. If y > 64, the result should
// always be 0.
//
// Breaking down the operation:
//
// (SLL x y) generates x << (y & 63).
//
// If y < 64, this is the value we want. Otherwise, we want zero.
//
// So, we AND with -1 * uint64(y < 64), which is 0xfffff... if y < 64 and 0 otherwise.
(Lsh8x8   <t> x y) => (AND (SLL <t> x y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Lsh8x16  <t> x y) => (AND (SLL <t> x y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Lsh8x32  <t> x y) => (AND (SLL <t> x y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Lsh8x64  <t> x y) => (AND (SLL <t> x y) (Neg8  <t> (SLTIU <t> [64] y)))
(Lsh16x8  <t> x y) => (AND (SLL <t> x y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Lsh16x16 <t> x y) => (AND (SLL <t> x y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Lsh16x32 <t> x y) => (AND (SLL <t> x y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Lsh16x64 <t> x y) => (AND (SLL <t> x y) (Neg16 <t> (SLTIU <t> [64] y)))
(Lsh32x8  <t> x y) => (AND (SLL <t> x y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Lsh32x16 <t> x y) => (AND (SLL <t> x y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Lsh32x32 <t> x y) => (AND (SLL <t> x y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Lsh32x64 <t> x y) => (AND (SLL <t> x y) (Neg32 <t> (SLTIU <t> [64] y)))
(Lsh64x8  <t> x y) => (AND (SLL <t> x y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Lsh64x16 <t> x y) => (AND (SLL <t> x y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Lsh64x32 <t> x y) => (AND (SLL <t> x y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Lsh64x64 <t> x y) => (AND (SLL <t> x y) (Neg64 <t> (SLTIU <t> [64] y)))

// SRL only considers the bottom 6 bits of y. If y > 64, the result should
// always be 0. See Lsh above for a detailed description.
(Rsh8Ux8   <t> x y) => (AND (SRL <t> (ZeroExt8to64  x) y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Rsh8Ux16  <t> x y) => (AND (SRL <t> (ZeroExt8to64  x) y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Rsh8Ux32  <t> x y) => (AND (SRL <t> (ZeroExt8to64  x) y) (Neg8  <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Rsh8Ux64  <t> x y) => (AND (SRL <t> (ZeroExt8to64  x) y) (Neg8  <t> (SLTIU <t> [64] y)))
(Rsh16Ux8  <t> x y) => (AND (SRL <t> (ZeroExt16to64 x) y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Rsh16Ux16 <t> x y) => (AND (SRL <t> (ZeroExt16to64 x) y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Rsh16Ux32 <t> x y) => (AND (SRL <t> (ZeroExt16to64 x) y) (Neg16 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Rsh16Ux64 <t> x y) => (AND (SRL <t> (ZeroExt16to64 x) y) (Neg16 <t> (SLTIU <t> [64] y)))
(Rsh32Ux8  <t> x y) => (AND (SRL <t> (ZeroExt32to64 x) y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Rsh32Ux16 <t> x y) => (AND (SRL <t> (ZeroExt32to64 x) y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Rsh32Ux32 <t> x y) => (AND (SRL <t> (ZeroExt32to64 x) y) (Neg32 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Rsh32Ux64 <t> x y) => (AND (SRL <t> (ZeroExt32to64 x) y) (Neg32 <t> (SLTIU <t> [64] y)))
(Rsh64Ux8  <t> x y) => (AND (SRL <t> x                 y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt8to64  y))))
(Rsh64Ux16 <t> x y) => (AND (SRL <t> x                 y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt16to64 y))))
(Rsh64Ux32 <t> x y) => (AND (SRL <t> x                 y) (Neg64 <t> (SLTIU <t> [64] (ZeroExt32to64 y))))
(Rsh64Ux64 <t> x y) => (AND (SRL <t> x                 y) (Neg64 <t> (SLTIU <t> [64] y)))

// SRA only considers the bottom 6 bits of y. If y > 64, the result should
// be either 0 or -1 based on the sign bit.
//
// We implement this by performing the max shift (-1) if y >= 64.
//
// We OR (uint64(y < 64) - 1) into y before passing it to SRA. This leaves
// us with -1 (0xffff...) if y >= 64.
//
// We don't need to sign-extend the OR result, as it will be at minimum 8 bits,
// more than the 6 bits SRA cares about.
(Rsh8x8   <t> x y) => (SRA <t> (SignExt8to64  x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt8to64  y)))))
(Rsh8x16  <t> x y) => (SRA <t> (SignExt8to64  x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt16to64 y)))))
(Rsh8x32  <t> x y) => (SRA <t> (SignExt8to64  x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt32to64 y)))))
(Rsh8x64  <t> x y) => (SRA <t> (SignExt8to64  x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] y))))
(Rsh16x8  <t> x y) => (SRA <t> (SignExt16to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt8to64  y)))))
(Rsh16x16 <t> x y) => (SRA <t> (SignExt16to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt16to64 y)))))
(Rsh16x32 <t> x y) => (SRA <t> (SignExt16to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt32to64 y)))))
(Rsh16x64 <t> x y) => (SRA <t> (SignExt16to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] y))))
(Rsh32x8  <t> x y) => (SRA <t> (SignExt32to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt8to64  y)))))
(Rsh32x16 <t> x y) => (SRA <t> (SignExt32to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt16to64 y)))))
(Rsh32x32 <t> x y) => (SRA <t> (SignExt32to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt32to64 y)))))
(Rsh32x64 <t> x y) => (SRA <t> (SignExt32to64 x) (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] y))))
(Rsh64x8  <t> x y) => (SRA <t> x                 (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt8to64  y)))))
(Rsh64x16 <t> x y) => (SRA <t> x                 (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt16to64 y)))))
(Rsh64x32 <t> x y) => (SRA <t> x                 (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] (ZeroExt32to64 y)))))
(Rsh64x64 <t> x y) => (SRA <t> x                 (OR <y.Type> y (ADDI <y.Type> [-1] (SLTIU <y.Type> [64] y))))

// rotates
(RotateLeft8  <t> x (MOVDconst [c])) => (Or8  (Lsh8x64  <t> x (MOVDconst [c&7]))  (Rsh8Ux64  <t> x (MOVDconst [-c&7])))
(RotateLeft16 <t> x (MOVDconst [c])) => (Or16 (Lsh16x64 <t> x (MOVDconst [c&15])) (Rsh16Ux64 <t> x (MOVDconst [-c&15])))
(RotateLeft32 <t> x (MOVDconst [c])) => (Or32 (Lsh32x64 <t> x (MOVDconst [c&31])) (Rsh32Ux64 <t> x (MOVDconst [-c&31])))
(RotateLeft64 <t> x (MOVDconst [c])) => (Or64 (Lsh64x64 <t> x (MOVDconst [c&63])) (Rsh64Ux64 <t> x (MOVDconst [-c&63])))

(Less64  ...) => (SLT  ...)
(Less32  x y) => (SLT  (SignExt32to64 x) (SignExt32to64 y))
(Less16  x y) => (SLT  (SignExt16to64 x) (SignExt16to64 y))
(Less8   x y) => (SLT  (SignExt8to64  x) (SignExt8to64  y))
(Less64U ...) => (SLTU ...)
(Less32U x y) => (SLTU (ZeroExt32to64 x) (ZeroExt32to64 y))
(Less16U x y) => (SLTU (ZeroExt16to64 x) (ZeroExt16to64 y))
(Less8U  x y) => (SLTU (ZeroExt8to64  x) (ZeroExt8to64  y))
(Less64F ...) => (FLTD ...)
(Less32F ...) => (FLTS ...)

// Convert x <= y to !(y > x).
(Leq64  x y) => (Not (Less64  y x))
(Leq32  x y) => (Not (Less32  y x))
(Leq16  x y) => (Not (Less16  y x))
(Leq8   x y) => (Not (Less8   y x))
(Leq64U x y) => (Not (Less64U y x))
(Leq32U x y) => (Not (Less32U y x))
(Leq16U x y) => (Not (Less16U y x))
(Leq8U  x y) => (Not (Less8U  y x))
(Leq64F ...) => (FLED ...)
(Leq32F ...) => (FLES ...)

(EqPtr x y) => (SEQZ (SUB <typ.Uintptr> x y))
(Eq64  x y) => (SEQZ (SUB <x.Type> x y))
(Eq32  x y) => (SEQZ (SUB <x.Type> (ZeroExt32to64 x) (ZeroExt32to64 y)))
(Eq16  x y) => (SEQZ (SUB <x.Type> (ZeroExt16to64 x) (ZeroExt16to64 y)))
(Eq8   x y) => (SEQZ (SUB <x.Type> (ZeroExt8to64  x) (ZeroExt8to64  y)))
(Eq64F ...) => (FEQD ...)
(Eq32F ...) => (FEQS ...)

(NeqPtr x y) => (SNEZ (SUB <typ.Uintptr> x y))
(Neq64  x y) => (SNEZ (SUB <x.Type> x y))
(Neq32  x y) => (SNEZ (SUB <x.Type> (ZeroExt32to64 x) (ZeroExt32to64 y)))
(Neq16  x y) => (SNEZ (SUB <x.Type> (ZeroExt16to64 x) (ZeroExt16to64 y)))
(Neq8   x y) => (SNEZ (SUB <x.Type> (ZeroExt8to64  x) (ZeroExt8to64  y)))
(Neq64F ...) => (FNED ...)
(Neq32F ...) => (FNES ...)

// Loads
(Load <t> ptr mem) &&  t.IsBoolean()                  => (MOVBUload ptr mem)
(Load <t> ptr mem) && ( is8BitInt(t) &&  isSigned(t)) => (MOVBload  ptr mem)
(Load <t> ptr mem) && ( is8BitInt(t) && !isSigned(t)) => (MOVBUload ptr mem)
(Load <t> ptr mem) && (is16BitInt(t) &&  isSigned(t)) => (MOVHload  ptr mem)
(Load <t> ptr mem) && (is16BitInt(t) && !isSigned(t)) => (MOVHUload ptr mem)
(Load <t> ptr mem) && (is32BitInt(t) &&  isSigned(t)) => (MOVWload  ptr mem)
(Load <t> ptr mem) && (is32BitInt(t) && !isSigned(t)) => (MOVWUload ptr mem)
(Load <t> ptr mem) && (is64BitInt(t) || isPtr(t))     => (MOVDload  ptr mem)
(Load <t> ptr mem) &&  is32BitFloat(t)                => (FMOVWload ptr mem)
(Load <t> ptr mem) &&  is64BitFloat(t)                => (FMOVDload ptr mem)

// Stores
(Store {t} ptr val mem) && t.Size() == 1 => (MOVBstore ptr val mem)
(Store {t} ptr val mem) && t.Size() == 2 => (MOVHstore ptr val mem)
(Store {t} ptr val mem) && t.Size() == 4 && !is32BitFloat(val.Type) => (MOVWstore ptr val mem)
(Store {t} ptr val mem) && t.Size() == 8 && !is64BitFloat(val.Type) => (MOVDstore ptr val mem)
(Store {t} ptr val mem) && t.Size() == 4 &&  is32BitFloat(val.Type) => (FMOVWstore ptr val mem)
(Store {t} ptr val mem) && t.Size() == 8 &&  is64BitFloat(val.Type) => (FMOVDstore ptr val mem)

// We need to fold MOVaddr into the LD/MOVDstore ops so that the live variable analysis
// knows what variables are being read/written by the ops.
(MOVBUload [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVBUload [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVBload  [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVBload  [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVHUload [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVHUload [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVHload  [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVHload  [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVWUload [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVWUload [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVWload  [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVWload  [off1+off2] {mergeSym(sym1,sym2)} base mem)
(MOVDload  [off1] {sym1} (MOVaddr [off2] {sym2} base) mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVDload  [off1+off2] {mergeSym(sym1,sym2)} base mem)

(MOVBstore [off1] {sym1} (MOVaddr [off2] {sym2} base) val mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVBstore [off1+off2] {mergeSym(sym1,sym2)} base val mem)
(MOVHstore [off1] {sym1} (MOVaddr [off2] {sym2} base) val mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVHstore [off1+off2] {mergeSym(sym1,sym2)} base val mem)
(MOVWstore [off1] {sym1} (MOVaddr [off2] {sym2} base) val mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVWstore [off1+off2] {mergeSym(sym1,sym2)} base val mem)
(MOVDstore [off1] {sym1} (MOVaddr [off2] {sym2} base) val mem) && is32Bit(int64(off1)+int64(off2)) && canMergeSym(sym1, sym2) =>
	(MOVDstore [off1+off2] {mergeSym(sym1,sym2)} base val mem)
(MOVBstorezero [off1] {sym1} (MOVaddr [off2] {sym2} ptr) mem) && canMergeSym(sym1,sym2) && is32Bit(int64(off1)+int64(off2)) =>
	(MOVBstorezero [off1+off2] {mergeSym(sym1,sym2)} ptr mem)
(MOVHstorezero [off1] {sym1} (MOVaddr [off2] {sym2} ptr) mem) && canMergeSym(sym1,sym2) && is32Bit(int64(off1)+int64(off2)) =>
	(MOVHstorezero [off1+off2] {mergeSym(sym1,sym2)} ptr mem)
(MOVWstorezero [off1] {sym1} (MOVaddr [off2] {sym2} ptr) mem) && canMergeSym(sym1,sym2) && is32Bit(int64(off1)+int64(off2)) =>
	(MOVWstorezero [off1+off2] {mergeSym(sym1,sym2)} ptr mem)
(MOVDstorezero [off1] {sym1} (MOVaddr [off2] {sym2} ptr) mem) && canMergeSym(sym1,sym2) && is32Bit(int64(off1)+int64(off2)) =>
	(MOVDstorezero [off1+off2] {mergeSym(sym1,sym2)} ptr mem)

(MOVBUload [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVBUload [off1+int32(off2)] {sym} base mem)
(MOVBload  [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVBload  [off1+int32(off2)] {sym} base mem)
(MOVHUload [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVHUload [off1+int32(off2)] {sym} base mem)
(MOVHload  [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVHload  [off1+int32(off2)] {sym} base mem)
(MOVWUload [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVWUload [off1+int32(off2)] {sym} base mem)
(MOVWload  [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVWload  [off1+int32(off2)] {sym} base mem)
(MOVDload  [off1] {sym} (ADDI [off2] base) mem) && is32Bit(int64(off1)+off2) =>
	(MOVDload  [off1+int32(off2)] {sym} base mem)

(MOVBstore [off1] {sym} (ADDI [off2] base) val mem) && is32Bit(int64(off1)+off2) =>
	(MOVBstore [off1+int32(off2)] {sym} base val mem)
(MOVHstore [off1] {sym} (ADDI [off2] base) val mem) && is32Bit(int64(off1)+off2) =>
	(MOVHstore [off1+int32(off2)] {sym} base val mem)
(MOVWstore [off1] {sym} (ADDI [off2] base) val mem) && is32Bit(int64(off1)+off2) =>
	(MOVWstore [off1+int32(off2)] {sym} base val mem)
(MOVDstore [off1] {sym} (ADDI [off2] base) val mem) && is32Bit(int64(off1)+off2) =>
	(MOVDstore [off1+int32(off2)] {sym} base val mem)
(MOVBstorezero [off1] {sym} (ADDI [off2] ptr) mem) && is32Bit(int64(off1)+off2) => (MOVBstorezero [off1+int32(off2)] {sym} ptr mem)
(MOVHstorezero [off1] {sym} (ADDI [off2] ptr) mem) && is32Bit(int64(off1)+off2) => (MOVHstorezero [off1+int32(off2)] {sym} ptr mem)
(MOVWstorezero [off1] {sym} (ADDI [off2] ptr) mem) && is32Bit(int64(off1)+off2) => (MOVWstorezero [off1+int32(off2)] {sym} ptr mem)
(MOVDstorezero [off1] {sym} (ADDI [off2] ptr) mem) && is32Bit(int64(off1)+off2) => (MOVDstorezero [off1+int32(off2)] {sym} ptr mem)

// Similarly, fold ADDI into MOVaddr to avoid confusing live variable analysis
// with OffPtr -> ADDI.
(ADDI [c] (MOVaddr [d] {s} x)) && is32Bit(c+int64(d)) => (MOVaddr [int32(c)+d] {s} x)

// Small zeroing
(Zero [0] _ mem) => mem
(Zero [1] ptr mem) => (MOVBstore ptr (MOVDconst [0]) mem)
(Zero [2] {t} ptr mem) && t.Alignment()%2 == 0 =>
	(MOVHstore ptr (MOVDconst [0]) mem)
(Zero [2] ptr mem) =>
	(MOVBstore [1] ptr (MOVDconst [0])
		(MOVBstore ptr (MOVDconst [0]) mem))
(Zero [4] {t} ptr mem) && t.Alignment()%4 == 0 =>
	(MOVWstore ptr (MOVDconst [0]) mem)
(Zero [4] {t} ptr mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [2] ptr (MOVDconst [0])
		(MOVHstore ptr (MOVDconst [0]) mem))
(Zero [4] ptr mem) =>
	(MOVBstore [3] ptr (MOVDconst [0])
		(MOVBstore [2] ptr (MOVDconst [0])
			(MOVBstore [1] ptr (MOVDconst [0])
				(MOVBstore ptr (MOVDconst [0]) mem))))
(Zero [8] {t} ptr mem) && t.Alignment()%8 == 0 =>
	(MOVDstore ptr (MOVDconst [0]) mem)
(Zero [8] {t} ptr mem) && t.Alignment()%4 == 0 =>
	(MOVWstore [4] ptr (MOVDconst [0])
		(MOVWstore ptr (MOVDconst [0]) mem))
(Zero [8] {t} ptr mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [6] ptr (MOVDconst [0])
		(MOVHstore [4] ptr (MOVDconst [0])
			(MOVHstore [2] ptr (MOVDconst [0])
				(MOVHstore ptr (MOVDconst [0]) mem))))

(Zero [3] ptr mem) =>
	(MOVBstore [2] ptr (MOVDconst [0])
		(MOVBstore [1] ptr (MOVDconst [0])
			(MOVBstore ptr (MOVDconst [0]) mem)))
(Zero [6] {t} ptr mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [4] ptr (MOVDconst [0])
		(MOVHstore [2] ptr (MOVDconst [0])
			(MOVHstore ptr (MOVDconst [0]) mem)))
(Zero [12] {t} ptr mem) && t.Alignment()%4 == 0 =>
	(MOVWstore [8] ptr (MOVDconst [0])
		(MOVWstore [4] ptr (MOVDconst [0])
			(MOVWstore ptr (MOVDconst [0]) mem)))
(Zero [16] {t} ptr mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [8] ptr (MOVDconst [0])
		(MOVDstore ptr (MOVDconst [0]) mem))
(Zero [24] {t} ptr mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [16] ptr (MOVDconst [0])
		(MOVDstore [8] ptr (MOVDconst [0])
			(MOVDstore ptr (MOVDconst [0]) mem)))
(Zero [32] {t} ptr mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [24] ptr (MOVDconst [0])
		(MOVDstore [16] ptr (MOVDconst [0])
			(MOVDstore [8] ptr (MOVDconst [0])
				(MOVDstore ptr (MOVDconst [0]) mem))))

// Medium 8-aligned zeroing uses a Duff's device
// 8 and 128 are magic constants, see runtime/mkduff.go
(Zero [s] {t} ptr mem)
	&& s%8 == 0 && s <= 8*128
	&& t.Alignment()%8 == 0 && !config.noDuffDevice =>
	(DUFFZERO [8 * (128 - s/8)] ptr mem)

// Generic zeroing uses a loop
(Zero [s] {t} ptr mem) =>
	(LoweredZero [t.Alignment()]
		ptr
		(ADD <ptr.Type> ptr (MOVDconst [s-moveSize(t.Alignment(), config)]))
		mem)

(Convert ...) => (MOVconvert ...)

// Checks
(IsNonNil ...) => (SNEZ ...)
(IsInBounds ...) => (Less64U ...)
(IsSliceInBounds ...) => (Leq64U ...)

// Trivial lowering
(NilCheck ...) => (LoweredNilCheck ...)
(GetClosurePtr ...) => (LoweredGetClosurePtr ...)
(GetCallerSP ...) => (LoweredGetCallerSP ...)
(GetCallerPC ...) => (LoweredGetCallerPC ...)

// Write barrier.
(WB ...) => (LoweredWB ...)

(PanicBounds [kind] x y mem) && boundsABI(kind) == 0 => (LoweredPanicBoundsA [kind] x y mem)
(PanicBounds [kind] x y mem) && boundsABI(kind) == 1 => (LoweredPanicBoundsB [kind] x y mem)
(PanicBounds [kind] x y mem) && boundsABI(kind) == 2 => (LoweredPanicBoundsC [kind] x y mem)

// Small moves
(Move [0] _ _ mem) => mem
(Move [1] dst src mem) => (MOVBstore dst (MOVBload src mem) mem)
(Move [2] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore dst (MOVHload src mem) mem)
(Move [2] dst src mem) =>
	(MOVBstore [1] dst (MOVBload [1] src mem)
		(MOVBstore dst (MOVBload src mem) mem))
(Move [4] {t} dst src mem) && t.Alignment()%4 == 0 =>
	(MOVWstore dst (MOVWload src mem) mem)
(Move [4] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [2] dst (MOVHload [2] src mem)
		(MOVHstore dst (MOVHload src mem) mem))
(Move [4] dst src mem) =>
	(MOVBstore [3] dst (MOVBload [3] src mem)
		(MOVBstore [2] dst (MOVBload [2] src mem)
			(MOVBstore [1] dst (MOVBload [1] src mem)
				(MOVBstore dst (MOVBload src mem) mem))))
(Move [8] {t} dst src mem) && t.Alignment()%8 == 0 =>
	(MOVDstore dst (MOVDload src mem) mem)
(Move [8] {t} dst src mem) && t.Alignment()%4 == 0 =>
	(MOVWstore [4] dst (MOVWload [4] src mem)
		(MOVWstore dst (MOVWload src mem) mem))
(Move [8] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [6] dst (MOVHload [6] src mem)
		(MOVHstore [4] dst (MOVHload [4] src mem)
			(MOVHstore [2] dst (MOVHload [2] src mem)
				(MOVHstore dst (MOVHload src mem) mem))))

(Move [3] dst src mem) =>
	(MOVBstore [2] dst (MOVBload [2] src mem)
		(MOVBstore [1] dst (MOVBload [1] src mem)
			(MOVBstore dst (MOVBload src mem) mem)))
(Move [6] {t} dst src mem) && t.Alignment()%2 == 0 =>
	(MOVHstore [4] dst (MOVHload [4] src mem)
		(MOVHstore [2] dst (MOVHload [2] src mem)
			(MOVHstore dst (MOVHload src mem) mem)))
(Move [12] {t} dst src mem) && t.Alignment()%4 == 0 =>
	(MOVWstore [8] dst (MOVWload [8] src mem)
		(MOVWstore [4] dst (MOVWload [4] src mem)
			(MOVWstore dst (MOVWload src mem) mem)))
(Move [16] {t} dst src mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [8] dst (MOVDload [8] src mem)
		(MOVDstore dst (MOVDload src mem) mem))
(Move [24] {t} dst src mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [16] dst (MOVDload [16] src mem)
		(MOVDstore [8] dst (MOVDload [8] src mem)
			(MOVDstore dst (MOVDload src mem) mem)))
(Move [32] {t} dst src mem) && t.Alignment()%8 == 0 =>
	(MOVDstore [24] dst (MOVDload [24] src mem)
		(MOVDstore [16] dst (MOVDload [16] src mem)
			(MOVDstore [8] dst (MOVDload [8] src mem)
				(MOVDstore dst (MOVDload src mem) mem))))

// Medium 8-aligned move uses a Duff's device
// 16 and 128 are magic constants, see runtime/mkduff.go
(Move [s] {t} dst src mem)
	&& s%8 == 0 && s <= 8*128 && t.Alignment()%8 == 0
	&& !config.noDuffDevice && logLargeCopy(v, s) =>
	(DUFFCOPY [16 * (128 - s/8)] dst src mem)

// Generic move uses a loop
(Move [s] {t} dst src mem) && (s <= 16 || logLargeCopy(v, s)) =>
	(LoweredMove [t.Alignment()]
		dst
		src
		(ADDI <src.Type> [s-moveSize(t.Alignment(), config)] src)
		mem)

// Boolean ops; 0=false, 1=true
(AndB ...) => (AND ...)
(OrB  ...) => (OR  ...)
(EqB  x y) => (SEQZ (XOR <typ.Bool> x y))
(NeqB ...) => (XOR ...)
(Not  ...) => (SEQZ ...)

// Lowering pointer arithmetic
// TODO: Special handling for SP offsets, like ARM
(OffPtr [off] ptr:(SP)) && is32Bit(off) => (MOVaddr [int32(off)] ptr)
(OffPtr [off] ptr) && is32Bit(off) => (ADDI [off] ptr)
(OffPtr [off] ptr) => (ADD (MOVDconst [off]) ptr)

(Const8  [val]) => (MOVDconst [int64(val)])
(Const16 [val]) => (MOVDconst [int64(val)])
(Const32 [val]) => (MOVDconst [int64(val)])
(Const64 [val]) => (MOVDconst [int64(val)])
(Const32F [val]) => (FMVSX (MOVDconst [int64(math.Float32bits(val))]))
(Const64F [val]) => (FMVDX (MOVDconst [int64(math.Float64bits(val))]))
(ConstNil) => (MOVDconst [0])
(ConstBool [val]) => (MOVDconst [int64(b2i(val))])

(Addr {sym} base) => (MOVaddr {sym} [0] base)
(LocalAddr {sym} base _) => (MOVaddr {sym} base)

// Calls
(StaticCall  ...) => (CALLstatic  ...)
(ClosureCall ...) => (CALLclosure ...)
(InterCall   ...) => (CALLinter   ...)

// Atomic Intrinsics
(AtomicLoad8   ...) => (LoweredAtomicLoad8  ...)
(AtomicLoad32  ...) => (LoweredAtomicLoad32 ...)
(AtomicLoad64  ...) => (LoweredAtomicLoad64 ...)
(AtomicLoadPtr ...) => (LoweredAtomicLoad64 ...)

(AtomicStore8       ...) => (LoweredAtomicStore8  ...)
(AtomicStore32      ...) => (LoweredAtomicStore32 ...)
(AtomicStore64      ...) => (LoweredAtomicStore64 ...)
(AtomicStorePtrNoWB ...) => (LoweredAtomicStore64 ...)

(AtomicAdd32 ...) => (LoweredAtomicAdd32 ...)
(AtomicAdd64 ...) => (LoweredAtomicAdd64 ...)

// AtomicAnd8(ptr,val) => LoweredAtomicAnd32(ptr&^3, ^((uint8(val) ^ 0xff) << ((ptr & 3) * 8)))
(AtomicAnd8 ptr val mem) =>
	(LoweredAtomicAnd32 (ANDI <typ.Uintptr> [^3] ptr)
		(NOT <typ.UInt32> (SLL <typ.UInt32> (XORI <typ.UInt32> [0xff] (ZeroExt8to32 val))
			(SLLI <typ.UInt64> [3] (ANDI <typ.UInt64> [3] ptr)))) mem)

(AtomicAnd32 ...) => (LoweredAtomicAnd32 ...)

(AtomicCompareAndSwap32 ...) => (LoweredAtomicCas32 ...)
(AtomicCompareAndSwap64 ...) => (LoweredAtomicCas64 ...)

(AtomicExchange32 ...) => (LoweredAtomicExchange32 ...)
(AtomicExchange64 ...) => (LoweredAtomicExchange64 ...)

// AtomicOr8(ptr,val)  => LoweredAtomicOr32(ptr&^3, uint32(val)<<((ptr&3)*8))
(AtomicOr8 ptr val mem) =>
	(LoweredAtomicOr32 (ANDI <typ.Uintptr> [^3] ptr)
		(SLL <typ.UInt32> (ZeroExt8to32 val)
			(SLLI <typ.UInt64> [3] (ANDI <typ.UInt64> [3] ptr))) mem)

(AtomicOr32  ...) => (LoweredAtomicOr32  ...)

// Conditional branches
(If cond yes no) => (BNEZ cond yes no)

// Optimizations

// Absorb SEQZ/SNEZ into branch.
(BEQZ (SEQZ x) yes no) => (BNEZ x yes no)
(BEQZ (SNEZ x) yes no) => (BEQZ x yes no)
(BNEZ (SEQZ x) yes no) => (BEQZ x yes no)
(BNEZ (SNEZ x) yes no) => (BNEZ x yes no)

// Convert BEQZ/BNEZ into more optimal branch conditions.
(BEQZ (SUB x y) yes no) => (BEQ x y yes no)
(BNEZ (SUB x y) yes no) => (BNE x y yes no)
(BEQZ (SLT x y) yes no) => (BGE x y yes no)
(BNEZ (SLT x y) yes no) => (BLT x y yes no)
(BEQZ (SLTU x y) yes no) => (BGEU x y yes no)
(BNEZ (SLTU x y) yes no) => (BLTU x y yes no)

// Convert branch with zero to BEQZ/BNEZ.
(BEQ (MOVDconst [0]) cond yes no) => (BEQZ cond yes no)
(BEQ cond (MOVDconst [0]) yes no) => (BEQZ cond yes no)
(BNE (MOVDconst [0]) cond yes no) => (BNEZ cond yes no)
(BNE cond (MOVDconst [0]) yes no) => (BNEZ cond yes no)

// Store zero
(MOVBstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVBstorezero [off] {sym} ptr mem)
(MOVHstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVHstorezero [off] {sym} ptr mem)
(MOVWstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVWstorezero [off] {sym} ptr mem)
(MOVDstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVDstorezero [off] {sym} ptr mem)

// Avoid sign/zero extension for consts.
(MOVBreg  (MOVDconst [c])) => (MOVDconst [int64(int8(c))])
(MOVHreg  (MOVDconst [c])) => (MOVDconst [int64(int16(c))])
(MOVWreg  (MOVDconst [c])) => (MOVDconst [int64(int32(c))])
(MOVBUreg (MOVDconst [c])) => (MOVDconst [int64(uint8(c))])
(MOVHUreg (MOVDconst [c])) => (MOVDconst [int64(uint16(c))])
(MOVWUreg (MOVDconst [c])) => (MOVDconst [int64(uint32(c))])

// Avoid sign/zero extension after properly typed load.
(MOVBreg  x:(MOVBload  _ _)) => (MOVDreg x)
(MOVHreg  x:(MOVBload  _ _)) => (MOVDreg x)
(MOVHreg  x:(MOVBUload _ _)) => (MOVDreg x)
(MOVHreg  x:(MOVHload  _ _)) => (MOVDreg x)
(MOVWreg  x:(MOVBload  _ _)) => (MOVDreg x)
(MOVWreg  x:(MOVBUload _ _)) => (MOVDreg x)
(MOVWreg  x:(MOVHload  _ _)) => (MOVDreg x)
(MOVWreg  x:(MOVHUload _ _)) => (MOVDreg x)
(MOVWreg  x:(MOVWload  _ _)) => (MOVDreg x)
(MOVBUreg x:(MOVBUload _ _)) => (MOVDreg x)
(MOVHUreg x:(MOVBUload _ _)) => (MOVDreg x)
(MOVHUreg x:(MOVHUload _ _)) => (MOVDreg x)
(MOVWUreg x:(MOVBUload _ _)) => (MOVDreg x)
(MOVWUreg x:(MOVHUload _ _)) => (MOVDreg x)
(MOVWUreg x:(MOVWUload _ _)) => (MOVDreg x)

// Fold double extensions.
(MOVBreg  x:(MOVBreg  _)) => (MOVDreg x)
(MOVHreg  x:(MOVBreg  _)) => (MOVDreg x)
(MOVHreg  x:(MOVBUreg _)) => (MOVDreg x)
(MOVHreg  x:(MOVHreg  _)) => (MOVDreg x)
(MOVWreg  x:(MOVBreg  _)) => (MOVDreg x)
(MOVWreg  x:(MOVBUreg _)) => (MOVDreg x)
(MOVWreg  x:(MOVHreg  _)) => (MOVDreg x)
(MOVWreg  x:(MOVWreg  _)) => (MOVDreg x)
(MOVBUreg x:(MOVBUreg _)) => (MOVDreg x)
(MOVHUreg x:(MOVBUreg _)) => (MOVDreg x)
(MOVHUreg x:(MOVHUreg _)) => (MOVDreg x)
(MOVWUreg x:(MOVBUreg _)) => (MOVDreg x)
(MOVWUreg x:(MOVHUreg _)) => (MOVDreg x)
(MOVWUreg x:(MOVWUreg _)) => (MOVDreg x)

// Do not extend before store.
(MOVBstore [off] {sym} ptr (MOVBreg  x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVBstore [off] {sym} ptr (MOVHreg  x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVBstore [off] {sym} ptr (MOVWreg  x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVBstore [off] {sym} ptr (MOVBUreg x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVBstore [off] {sym} ptr (MOVHUreg x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVBstore [off] {sym} ptr (MOVWUreg x) mem) => (MOVBstore [off] {sym} ptr x mem)
(MOVHstore [off] {sym} ptr (MOVHreg  x) mem) => (MOVHstore [off] {sym} ptr x mem)
(MOVHstore [off] {sym} ptr (MOVWreg  x) mem) => (MOVHstore [off] {sym} ptr x mem)
(MOVHstore [off] {sym} ptr (MOVHUreg x) mem) => (MOVHstore [off] {sym} ptr x mem)
(MOVHstore [off] {sym} ptr (MOVWUreg x) mem) => (MOVHstore [off] {sym} ptr x mem)
(MOVWstore [off] {sym} ptr (MOVWreg  x) mem) => (MOVWstore [off] {sym} ptr x mem)
(MOVWstore [off] {sym} ptr (MOVWUreg x) mem) => (MOVWstore [off] {sym} ptr x mem)

// Replace extend after load with alternate load where possible.
(MOVBreg  <t> x:(MOVBUload [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVBload  <t> [off] {sym} ptr mem)
(MOVHreg  <t> x:(MOVHUload [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVHload  <t> [off] {sym} ptr mem)
(MOVWreg  <t> x:(MOVWUload [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVWload  <t> [off] {sym} ptr mem)
(MOVBUreg <t> x:(MOVBload  [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVBUload <t> [off] {sym} ptr mem)
(MOVHUreg <t> x:(MOVHload  [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVHUload <t> [off] {sym} ptr mem)
(MOVWUreg <t> x:(MOVWload  [off] {sym} ptr mem)) && x.Uses == 1 && clobber(x) => @x.Block (MOVWUload <t> [off] {sym} ptr mem)

// If a register move has only 1 use, just use the same register without emitting instruction
// MOVnop does not emit an instruction, only for ensuring the type.
(MOVDreg x) && x.Uses == 1 => (MOVDnop x)

// TODO: we should be able to get rid of MOVDnop all together.
// But for now, this is enough to get rid of lots of them.
(MOVDnop (MOVDconst [c])) => (MOVDconst [c])

// Fold constant into immediate instructions where possible.
(ADD (MOVDconst [val]) x) && is32Bit(val) => (ADDI [val] x)
(AND (MOVDconst [val]) x) && is32Bit(val) => (ANDI [val] x)
(OR  (MOVDconst [val]) x) && is32Bit(val) => (ORI  [val] x)
(XOR (MOVDconst [val]) x) && is32Bit(val) => (XORI [val] x)
(SLL x (MOVDconst [val])) => (SLLI [int64(val&63)] x)
(SRL x (MOVDconst [val])) => (SRLI [int64(val&63)] x)
(SRA x (MOVDconst [val])) => (SRAI [int64(val&63)] x)

// Convert subtraction of a const into ADDI with negative immediate, where possible.
(SUB x (MOVDconst [val])) && is32Bit(-val) => (ADDI [-val] x)

// Subtraction of zero.
(SUB x (MOVDconst [0])) => x

// Subtraction of zero with sign extension.
(SUBW x (MOVDconst [0])) => (ADDIW [0] x)

// Subtraction from zero.
(SUB (MOVDconst [0]) x) => (NEG x)

// Subtraction from zero with sign extension.
(SUBW (MOVDconst [0]) x) => (NEGW x)

// Addition of zero.
(ADDI [0] x) => x