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Refactor some math functions into a shared file for rgbasm and rgblink

Fixes #769

Fixes #770

--- a/Makefile

+++ b/Makefile

@@ -72,7 +72,8 @@

 	src/extern/getopt.o \

 	src/extern/utf8decoder.o \

 	src/hashmap.o \

-	src/linkdefs.o

+	src/linkdefs.o \

+	src/opmath.o

 src/asm/lexer.o src/asm/main.o: src/asm/parser.h

@@ -88,7 +89,8 @@

 	src/extern/err.o \

 	src/extern/getopt.o \

 	src/hashmap.o \

-	src/linkdefs.o

+	src/linkdefs.o \

+	src/opmath.o

 rgbfix_obj := \

 	src/fix/main.o \

--- /dev/null

+++ b/include/opmath.h

@@ -1,0 +1,20 @@

+/*

+ * This file is part of RGBDS.

+ *

+ * Copyright (c) 1997-2021, RGBDS contributors.

+ *

+ * SPDX-License-Identifier: MIT

+ */

+

+#ifndef RGBDS_OP_MATH_H

+#define RGBDS_OP_MATH_H

+

+#include <stdint.h>

+

+int32_t op_divide(int32_t dividend, int32_t divisor);

+int32_t op_modulo(int32_t dividend, int32_t divisor);

+int32_t op_exponent(int32_t base, uint32_t power);

+int32_t op_shift_left(int32_t value, int32_t amount);

+int32_t op_shift_right(int32_t value, int32_t amount);

+

+#endif /* RGBDS_OP_MATH_H */

--- a/src/CMakeLists.txt

+++ b/src/CMakeLists.txt

@@ -60,6 +60,7 @@

     "extern/utf8decoder.c"

     "hashmap.c"

     "linkdefs.c"

+    "opmath.c"

     )

 set(rgbfix_src

@@ -83,6 +84,7 @@

     "link/symbol.c"

     "hashmap.c"

     "linkdefs.c"

+    "opmath.c"

     )

 foreach(PROG "asm" "fix" "gfx" "link")

--- a/src/asm/rpn.c

+++ b/src/asm/rpn.c

@@ -25,6 +25,8 @@

 #include "asm/symbol.h"

 #include "asm/warning.h"

+#include "opmath.h"

+

 /* Makes an expression "not known", also setting its error message */

 #define makeUnknown(expr_, ...) do { \

 	struct Expression *_expr = expr_; \

@@ -244,77 +246,6 @@

 	}

 }

-static int32_t shift(int32_t shiftee, int32_t amount)

-{

-	if (amount >= 0) {

-		// Left shift

-		if (amount >= 32) {

-			warning(WARNING_SHIFT_AMOUNT, "Shifting left by large amount %"

-				PRId32 "\n", amount);

-			return 0;

-

-		} else {

-			/*

-			 * Use unsigned to force a bitwise shift

-			 * Casting back is OK because the types implement two's

-			 * complement behavior

-			 */

-			return (uint32_t)shiftee << amount;

-		}

-	} else {

-		// Right shift

-		amount = -amount;

-		if (amount >= 32) {

-			warning(WARNING_SHIFT_AMOUNT,

-				"Shifting right by large amount %" PRId32 "\n", amount);

-			return shiftee < 0 ? -1 : 0;

-

-		} else if (shiftee >= 0) {

-			return shiftee >> amount;

-

-		} else {

-			/*

-			 * The C standard leaves shifting right negative values

-			 * undefined, so use a left shift manually sign-extended

-			 */

-			return (uint32_t)shiftee >> amount

-				| -(UINT32_C(1) << (32 - amount));

-		}

-	}

-}

-

-static int32_t divide(int32_t dividend, int32_t divisor)

-{

-	// Adjust division to floor toward negative infinity,

-	// not truncate toward zero

-	return dividend / divisor - ((dividend % divisor < 0) != (divisor < 0));

-}

-

-static int32_t modulo(int32_t dividend, int32_t divisor)

-{

-	int32_t remainder = dividend % divisor;

-

-	// Adjust modulo to have the sign of the divisor,

-	// not the sign of the dividend

-	return remainder + divisor * ((remainder < 0) != (divisor < 0));

-}

-

-static int32_t exponent(int32_t base, uint32_t power)

-{

-	int32_t result = 1;

-

-	for (;;) {

-		if (power % 2)

-			result *= base;

-		power /= 2;

-		if (!power)

-			break;

-		base *= base;

-	}

-

-	return result;

-}

-

 struct Symbol const *rpn_SymbolOf(struct Expression const *expr)

 {

 	if (!rpn_isSymbol(expr))

@@ -400,11 +331,17 @@

 					"Shifting left by negative amount %" PRId32 "\n",

 					src2->nVal);

-			expr->nVal = shift(src1->nVal, src2->nVal);

+			if (src2->nVal >= 32)

+				warning(WARNING_SHIFT_AMOUNT,

+					"Shifting left by large amount %" PRId32 "\n",

+					src2->nVal);

+

+			expr->nVal = op_shift_left(src1->nVal, src2->nVal);

 			break;

 		case RPN_SHR:

 			if (src1->nVal < 0)

-				warning(WARNING_SHIFT, "Shifting negative value %" PRId32 "\n",

+				warning(WARNING_SHIFT, "Shifting right negative value %"

+					PRId32 "\n",

 					src1->nVal);

 			if (src2->nVal < 0)

@@ -412,7 +349,12 @@

 					"Shifting right by negative amount %" PRId32 "\n",

 					src2->nVal);

-			expr->nVal = shift(src1->nVal, -src2->nVal);

+			if (src2->nVal >= 32)

+				warning(WARNING_SHIFT_AMOUNT,

+					"Shifting right by large amount %" PRId32 "\n",

+					src2->nVal);

+

+			expr->nVal = op_shift_right(src1->nVal, src2->nVal);

 			break;

 		case RPN_MUL:

 			expr->nVal = uleft * uright;

@@ -426,7 +368,7 @@

 					PRId32 "\n", INT32_MIN, INT32_MIN);

 				expr->nVal = INT32_MIN;

 			} else {

-				expr->nVal = divide(src1->nVal, src2->nVal);

+				expr->nVal = op_divide(src1->nVal, src2->nVal);

 			}

 			break;

 		case RPN_MOD:

@@ -436,7 +378,7 @@

 			if (src1->nVal == INT32_MIN && src2->nVal == -1)

 				expr->nVal = 0;

 			else

-				expr->nVal = modulo(src1->nVal, src2->nVal);

+				expr->nVal = op_modulo(src1->nVal, src2->nVal);

 			break;

 		case RPN_EXP:

 			if (src2->nVal < 0)

@@ -445,7 +387,7 @@

 			if (src1->nVal == INT32_MIN && src2->nVal == -1)

 				expr->nVal = 0;

 			else

-				expr->nVal = exponent(src1->nVal, src2->nVal);

+				expr->nVal = op_exponent(src1->nVal, src2->nVal);

 			break;

 		case RPN_UNSUB:

--- a/src/link/patch.c

+++ b/src/link/patch.c

@@ -18,82 +18,10 @@

 #include "link/symbol.h"

 #include "linkdefs.h"

+#include "opmath.h"

 #include "extern/err.h"

-static int32_t divide(int32_t dividend, int32_t divisor)

-{

-	// Adjust division to floor toward negative infinity,

-	// not truncate toward zero

-	return dividend / divisor - ((dividend % divisor < 0) != (divisor < 0));

-}

-

-static int32_t modulo(int32_t dividend, int32_t divisor)

-{

-	int32_t remainder = dividend % divisor;

-

-	// Adjust modulo to have the sign of the divisor,

-	// not the sign of the dividend

-	return remainder + divisor * ((remainder < 0) != (divisor < 0));

-}

-

-static int32_t exponent(int32_t base, uint32_t power)

-{

-	int32_t result = 1;

-

-	for (;;) {

-		if (power % 2)

-			result *= base;

-		power /= 2;

-		if (!power)

-			break;

-		base *= base;

-	}

-

-	return result;

-}

-

-static int32_t asl(int32_t value, int32_t shiftamt); // Forward decl for below

-static int32_t asr(int32_t value, int32_t shiftamt)

-{

-	uint32_t uvalue = value;

-

-	// Get the easy cases out of the way

-	if (shiftamt == 0)

-		return value;

-	if (value == 0 || shiftamt <= -32)

-		return 0;

-	if (shiftamt > 31)

-		return (value < 0) ? -1 : 0;

-	if (shiftamt < 0)

-		return asl(value, -shiftamt);

-	if (value > 0)

-		return uvalue >> shiftamt;

-

-	{

-		// Calculate an OR mask for sign extension

-		// 1->0x80000000, 2->0xC0000000, ..., 31->0xFFFFFFFE

-		uint32_t shiftamt_high_bits = -((uint32_t)1 << (32 - shiftamt));

-

-		return (uvalue >> shiftamt) | shiftamt_high_bits;

-	}

-}

-

-static int32_t asl(int32_t value, int32_t shiftamt)

-{

-	// Repeat the easy cases here to avoid INT_MIN funny business

-	if (shiftamt == 0)

-		return value;

-	if (value == 0 || shiftamt >= 32)

-		return 0;

-	if (shiftamt < -31)

-		return (value < 0) ? -1 : 0;

-	if (shiftamt < 0)

-		return asr(value, -shiftamt);

-

-	return (uint32_t)value << shiftamt;

-}

-

 /*

  * This is an "empty"-type stack. Apart from the actual values, we also remember

  * whether the value is a placeholder inserted for error recovery. This allows

@@ -251,7 +179,7 @@

 				popRPN();

 				value = INT32_MAX;

 			} else {

-				value = divide(popRPN(), value);

+				value = op_divide(popRPN(), value);

 			}

 			break;

 		case RPN_MOD:

@@ -263,7 +191,7 @@

 				popRPN();

 				value = 0;

 			} else {

-				value = modulo(popRPN(), value);

+				value = op_modulo(popRPN(), value);

 			}

 			break;

 		case RPN_UNSUB:

@@ -278,7 +206,7 @@

 				popRPN();

 				value = 0;

 			} else {

-				value = exponent(popRPN(), value);

+				value = op_exponent(popRPN(), value);

 			}

 			break;

@@ -332,11 +260,11 @@

 		case RPN_SHL:

 			value = popRPN();

-			value = asl(popRPN(), value);

+			value = op_shift_left(popRPN(), value);

 			break;

 		case RPN_SHR:

 			value = popRPN();

-			value = asr(popRPN(), value);

+			value = op_shift_right(popRPN(), value);

 			break;

 		case RPN_BANK_SYM:

--- /dev/null

+++ b/src/opmath.c

@@ -1,0 +1,88 @@

+/*

+ * This file is part of RGBDS.

+ *

+ * Copyright (c) 1997-2021, RGBDS contributors.

+ *

+ * SPDX-License-Identifier: MIT

+ */

+

+/*

+ * Mathematical operators that don't reuse C's behavior

+ */

+

+#include <stdint.h>

+

+#include "opmath.h"

+

+int32_t op_divide(int32_t dividend, int32_t divisor)

+{

+	// Adjust division to floor toward negative infinity,

+	// not truncate toward zero

+	return dividend / divisor - ((dividend % divisor < 0) != (divisor < 0));

+}

+

+int32_t op_modulo(int32_t dividend, int32_t divisor)

+{

+	int32_t remainder = dividend % divisor;

+

+	// Adjust modulo to have the sign of the divisor,

+	// not the sign of the dividend

+	return remainder + divisor * ((remainder < 0) != (divisor < 0));

+}

+

+int32_t op_exponent(int32_t base, uint32_t power)

+{

+	int32_t result = 1;

+

+	for (;;) {

+		if (power % 2)

+			result *= base;

+		power /= 2;

+		if (!power)

+			break;

+		base *= base;

+	}

+

+	return result;

+}

+

+int32_t op_shift_left(int32_t value, int32_t amount)

+{

+	// Get the easy cases out of the way

+	if (amount == 0)

+		return value;

+	if (value == 0 || amount >= 32)

+		return 0;

+	if (amount < -31)

+		return (value < 0) ? -1 : 0;

+	if (amount < 0)

+		return op_shift_right(value, -amount);

+

+	// Use unsigned to force a bitwise shift

+	// Casting back is OK because the types implement two's complement behavior

+	return (uint32_t)value << amount;

+}

+

+int32_t op_shift_right(int32_t value, int32_t amount)

+{

+	// Repeat the easy cases here to avoid INT_MIN funny business

+	if (amount == 0)

+		return value;

+	if (value == 0 || amount <= -32)

+		return 0;

+	if (amount > 31)

+		return (value < 0) ? -1 : 0;

+	if (amount < 0)

+		return op_shift_left(value, -amount);

+

+	if (value > 0)

+		return (uint32_t)value >> amount;

+

+	// Calculate an OR mask for sign extension

+	// 1->0x80000000, 2->0xC0000000, ..., 31->0xFFFFFFFE

+	uint32_t amount_high_bits = -(UINT32_C(1) << (32 - amount));

+

+	// The C standard leaves shifting right negative values

+	// undefined, so use a left shift manually sign-extended

+	return ((uint32_t)value >> amount) | amount_high_bits;

+}

--- a/test/asm/shift.err

+++ b/test/asm/shift.err

@@ -12,49 +12,41 @@

     Shifting left by large amount 32

 warning: shift.asm(17) -> shift.asm::test(3): [-Wshift-amount]

     Shifting left by negative amount -9001

-warning: shift.asm(17) -> shift.asm::test(3): [-Wshift-amount]

-    Shifting right by large amount 9001

 warning: shift.asm(17) -> shift.asm::test(6): [-Wshift-amount]

     Shifting left by negative amount -9001

-warning: shift.asm(17) -> shift.asm::test(6): [-Wshift-amount]

-    Shifting right by large amount 9001

 warning: shift.asm(19) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(19) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(20) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(20) -> shift.asm::test(3): [-Wshift-amount]

     Shifting right by large amount 32

 warning: shift.asm(20) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(20) -> shift.asm::test(6): [-Wshift-amount]

     Shifting right by large amount 32

 warning: shift.asm(21) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(21) -> shift.asm::test(3): [-Wshift-amount]

     Shifting right by large amount 9001

 warning: shift.asm(21) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(21) -> shift.asm::test(6): [-Wshift-amount]

     Shifting right by large amount 9001

 warning: shift.asm(22) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -4

+    Shifting right negative value -4

 warning: shift.asm(22) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -4

+    Shifting right negative value -4

 warning: shift.asm(23) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -4

+    Shifting right negative value -4

 warning: shift.asm(23) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -4

+    Shifting right negative value -4

 warning: shift.asm(24) -> shift.asm::test(3): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(24) -> shift.asm::test(3): [-Wshift-amount]

     Shifting right by negative amount -9001

-warning: shift.asm(24) -> shift.asm::test(3): [-Wshift-amount]

-    Shifting left by large amount 9001

 warning: shift.asm(24) -> shift.asm::test(6): [-Wshift]

-    Shifting negative value -1

+    Shifting right negative value -1

 warning: shift.asm(24) -> shift.asm::test(6): [-Wshift-amount]

     Shifting right by negative amount -9001

-warning: shift.asm(24) -> shift.asm::test(6): [-Wshift-amount]

-    Shifting left by large amount 9001