gtsocial-umbx

arm.go (6328B)

---

 // Copyright 2015 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.
 
 // This file encapsulates some of the odd characteristics of the ARM
 // instruction set, to minimize its interaction with the core of the
 // assembler.
 
 package arch
 
 import (
 	"strings"
 
 	"github.com/twitchyliquid64/golang-asm/obj"
 	"github.com/twitchyliquid64/golang-asm/obj/arm"
 )
 
 var armLS = map[string]uint8{
 	"U":  arm.C_UBIT,
 	"S":  arm.C_SBIT,
 	"W":  arm.C_WBIT,
 	"P":  arm.C_PBIT,
 	"PW": arm.C_WBIT | arm.C_PBIT,
 	"WP": arm.C_WBIT | arm.C_PBIT,
 }
 
 var armSCOND = map[string]uint8{
 	"EQ":  arm.C_SCOND_EQ,
 	"NE":  arm.C_SCOND_NE,
 	"CS":  arm.C_SCOND_HS,
 	"HS":  arm.C_SCOND_HS,
 	"CC":  arm.C_SCOND_LO,
 	"LO":  arm.C_SCOND_LO,
 	"MI":  arm.C_SCOND_MI,
 	"PL":  arm.C_SCOND_PL,
 	"VS":  arm.C_SCOND_VS,
 	"VC":  arm.C_SCOND_VC,
 	"HI":  arm.C_SCOND_HI,
 	"LS":  arm.C_SCOND_LS,
 	"GE":  arm.C_SCOND_GE,
 	"LT":  arm.C_SCOND_LT,
 	"GT":  arm.C_SCOND_GT,
 	"LE":  arm.C_SCOND_LE,
 	"AL":  arm.C_SCOND_NONE,
 	"U":   arm.C_UBIT,
 	"S":   arm.C_SBIT,
 	"W":   arm.C_WBIT,
 	"P":   arm.C_PBIT,
 	"PW":  arm.C_WBIT | arm.C_PBIT,
 	"WP":  arm.C_WBIT | arm.C_PBIT,
 	"F":   arm.C_FBIT,
 	"IBW": arm.C_WBIT | arm.C_PBIT | arm.C_UBIT,
 	"IAW": arm.C_WBIT | arm.C_UBIT,
 	"DBW": arm.C_WBIT | arm.C_PBIT,
 	"DAW": arm.C_WBIT,
 	"IB":  arm.C_PBIT | arm.C_UBIT,
 	"IA":  arm.C_UBIT,
 	"DB":  arm.C_PBIT,
 	"DA":  0,
 }
 
 var armJump = map[string]bool{
 	"B":    true,
 	"BL":   true,
 	"BX":   true,
 	"BEQ":  true,
 	"BNE":  true,
 	"BCS":  true,
 	"BHS":  true,
 	"BCC":  true,
 	"BLO":  true,
 	"BMI":  true,
 	"BPL":  true,
 	"BVS":  true,
 	"BVC":  true,
 	"BHI":  true,
 	"BLS":  true,
 	"BGE":  true,
 	"BLT":  true,
 	"BGT":  true,
 	"BLE":  true,
 	"CALL": true,
 	"JMP":  true,
 }
 
 func jumpArm(word string) bool {
 	return armJump[word]
 }
 
 // IsARMCMP reports whether the op (as defined by an arm.A* constant) is
 // one of the comparison instructions that require special handling.
 func IsARMCMP(op obj.As) bool {
 	switch op {
 	case arm.ACMN, arm.ACMP, arm.ATEQ, arm.ATST:
 		return true
 	}
 	return false
 }
 
 // IsARMSTREX reports whether the op (as defined by an arm.A* constant) is
 // one of the STREX-like instructions that require special handling.
 func IsARMSTREX(op obj.As) bool {
 	switch op {
 	case arm.ASTREX, arm.ASTREXD, arm.ASWPW, arm.ASWPBU:
 		return true
 	}
 	return false
 }
 
 // MCR is not defined by the obj/arm; instead we define it privately here.
 // It is encoded as an MRC with a bit inside the instruction word,
 // passed to arch.ARMMRCOffset.
 const aMCR = arm.ALAST + 1
 
 // IsARMMRC reports whether the op (as defined by an arm.A* constant) is
 // MRC or MCR
 func IsARMMRC(op obj.As) bool {
 	switch op {
 	case arm.AMRC, aMCR: // Note: aMCR is defined in this package.
 		return true
 	}
 	return false
 }
 
 // IsARMBFX reports whether the op (as defined by an arm.A* constant) is one the
 // BFX-like instructions which are in the form of "op $width, $LSB, (Reg,) Reg".
 func IsARMBFX(op obj.As) bool {
 	switch op {
 	case arm.ABFX, arm.ABFXU, arm.ABFC, arm.ABFI:
 		return true
 	}
 	return false
 }
 
 // IsARMFloatCmp reports whether the op is a floating comparison instruction.
 func IsARMFloatCmp(op obj.As) bool {
 	switch op {
 	case arm.ACMPF, arm.ACMPD:
 		return true
 	}
 	return false
 }
 
 // ARMMRCOffset implements the peculiar encoding of the MRC and MCR instructions.
 // The difference between MRC and MCR is represented by a bit high in the word, not
 // in the usual way by the opcode itself. Asm must use AMRC for both instructions, so
 // we return the opcode for MRC so that asm doesn't need to import obj/arm.
 func ARMMRCOffset(op obj.As, cond string, x0, x1, x2, x3, x4, x5 int64) (offset int64, op0 obj.As, ok bool) {
 	op1 := int64(0)
 	if op == arm.AMRC {
 		op1 = 1
 	}
 	bits, ok := ParseARMCondition(cond)
 	if !ok {
 		return
 	}
 	offset = (0xe << 24) | // opcode
 		(op1 << 20) | // MCR/MRC
 		((int64(bits) ^ arm.C_SCOND_XOR) << 28) | // scond
 		((x0 & 15) << 8) | //coprocessor number
 		((x1 & 7) << 21) | // coprocessor operation
 		((x2 & 15) << 12) | // ARM register
 		((x3 & 15) << 16) | // Crn
 		((x4 & 15) << 0) | // Crm
 		((x5 & 7) << 5) | // coprocessor information
 		(1 << 4) /* must be set */
 	return offset, arm.AMRC, true
 }
 
 // IsARMMULA reports whether the op (as defined by an arm.A* constant) is
 // MULA, MULS, MMULA, MMULS, MULABB, MULAWB or MULAWT, the 4-operand instructions.
 func IsARMMULA(op obj.As) bool {
 	switch op {
 	case arm.AMULA, arm.AMULS, arm.AMMULA, arm.AMMULS, arm.AMULABB, arm.AMULAWB, arm.AMULAWT:
 		return true
 	}
 	return false
 }
 
 var bcode = []obj.As{
 	arm.ABEQ,
 	arm.ABNE,
 	arm.ABCS,
 	arm.ABCC,
 	arm.ABMI,
 	arm.ABPL,
 	arm.ABVS,
 	arm.ABVC,
 	arm.ABHI,
 	arm.ABLS,
 	arm.ABGE,
 	arm.ABLT,
 	arm.ABGT,
 	arm.ABLE,
 	arm.AB,
 	obj.ANOP,
 }
 
 // ARMConditionCodes handles the special condition code situation for the ARM.
 // It returns a boolean to indicate success; failure means cond was unrecognized.
 func ARMConditionCodes(prog *obj.Prog, cond string) bool {
 	if cond == "" {
 		return true
 	}
 	bits, ok := ParseARMCondition(cond)
 	if !ok {
 		return false
 	}
 	/* hack to make B.NE etc. work: turn it into the corresponding conditional */
 	if prog.As == arm.AB {
 		prog.As = bcode[(bits^arm.C_SCOND_XOR)&0xf]
 		bits = (bits &^ 0xf) | arm.C_SCOND_NONE
 	}
 	prog.Scond = bits
 	return true
 }
 
 // ParseARMCondition parses the conditions attached to an ARM instruction.
 // The input is a single string consisting of period-separated condition
 // codes, such as ".P.W". An initial period is ignored.
 func ParseARMCondition(cond string) (uint8, bool) {
 	return parseARMCondition(cond, armLS, armSCOND)
 }
 
 func parseARMCondition(cond string, ls, scond map[string]uint8) (uint8, bool) {
 	cond = strings.TrimPrefix(cond, ".")
 	if cond == "" {
 		return arm.C_SCOND_NONE, true
 	}
 	names := strings.Split(cond, ".")
 	bits := uint8(0)
 	for _, name := range names {
 		if b, present := ls[name]; present {
 			bits |= b
 			continue
 		}
 		if b, present := scond[name]; present {
 			bits = (bits &^ arm.C_SCOND) | b
 			continue
 		}
 		return 0, false
 	}
 	return bits, true
 }
 
 func armRegisterNumber(name string, n int16) (int16, bool) {
 	if n < 0 || 15 < n {
 		return 0, false
 	}
 	switch name {
 	case "R":
 		return arm.REG_R0 + n, true
 	case "F":
 		return arm.REG_F0 + n, true
 	}
 	return 0, false
 }