implemented logbf in asm and optimized ilogbf and copysignl

Author: ZERICO2005

src/libc/copysignl.src

@@ -6,7 +6,8 @@
 _copysignl:
 	ld	hl, 19	; upper 8 bits of y
 	add	hl, sp
-	rl	(hl)	; extract the signbit of y
+	ld	a, (hl)	; extract the signbit of y
+	rlca
 	pop	iy, hl, de, bc
 	push	bc, de, hl
 	rl	b	; clear the signbit of x, signbit of y is in the LSB

src/libc/ilogbf.src

@@ -13,48 +13,40 @@ _ilogbf:
 	dec	hl
 	dec	hl
 	dec	hl
-	ld	de, (hl)
-	sbc	hl, hl
-	ex	de, hl
-	; DE is zero
+	ld	hl, (hl)
 	add	hl, hl
-
 	adc	a, a
 	jr	z, .maybe_subnormal
 	inc	a
-	scf
 	jr	z, .inf_nan
-	rr	e	; E = 128 or float32_bias + 1
+	sub	a, 128	; float32_bias + 1
 	sbc	hl, hl
 	ld	l, a
-	sbc	hl, de
 	ret
 
 .maybe_subnormal:
-	; DE is zero, Carry unknown
 	add	hl, de
+	or	a, a
 	sbc	hl, de
 	jr	z, .ret_zero
 	call	__ictlz
-	ex	de, hl
-	;	DE was zero, so HL is now zero
-	dec	hl
 	cpl
 	add	a, 130
+	sbc	hl, hl
 	ld	l, a
 	ret
 
-.ret_zero:
 .inf_nan:
- 	ld	hl, $800000	; FP_ILOGB0
-	sbc	hl, de	; FP_ILOGBNAN or INT_MAX when carry is set
-	ex	de, hl
-	;	DE was zero, so HL is now zero
-	ld	l, 4	; EDOM
+	scf
+.ret_zero:
+	ld	hl, 4	; EDOM
 	ld	(_errno), hl
 	ld	hl, ___fe_cur_env
 	set	4, (hl)	; FE_INVALID
-	ex	de, hl
+	ld	hl, $800000	; FP_ILOGB0
+	ret	nc
+	; FP_ILOGBNAN or INT_MAX when carry is set
+	dec	hl
 	ret
 
 	extern	_errno

src/libc/logb.c

@@ -1,6 +1,10 @@
 #include <fenv.h>
 #include <math.h>
 
+#if 0
+
+/* logbf.src */
+
 float logbf(float x) {
     if (isfinite(x)) {
         if (iszero(x)) {
@@ -15,6 +19,8 @@ float logbf(float x) {
 
 double logb(double) __attribute__((alias("logbf")));
 
+#endif
+
 long double logbl(long double x) {
     if (isfinite(x)) {
         if (iszero(x)) {

src/libc/logbf.src

@@ -0,0 +1,68 @@
+	assume	adl=1
+
+	section	.text
+
+	public	_logbf, _logb
+
+; float logbf(float)
+_logb:
+_logbf:
+	ld	hl, 6
+	ld	bc, -3
+	add	hl, sp
+	ld	a, (hl)
+	add	hl, bc
+	ld	c, b	; ld bc, -1
+	ld	hl, (hl)
+	add	hl, hl
+	adc	a, a
+	jr	z, .maybe_subnormal
+	inc	a
+	jr	z, .inf_nan
+	sub	a, 128	; float32_bias + 1
+	jr	c, .negative_exponent
+	inc	bc	; ld bc, 0
+.negative_exponent:
+.int_to_float:
+	; exponent is [-149, 127]
+	ld	c, a
+	ld	a, b	; sign extend
+	call	__ltof
+	push	bc
+	pop	hl
+	ld	e, a
+	ret
+
+.inf_nan:
+	; return fabsf(x)
+	pop	bc
+	ex	(sp), hl
+	push	bc
+	ld	e, $7F
+	ret
+
+.ret_zero:
+	; HL is zero here
+	ld	l, 4	; EDOM
+	ld	(_errno), hl
+	; FE_DIVBYZERO
+	ld	hl, ___fe_cur_env
+	set	6, (hl)
+	; -HUGE_VALF
+	ld	hl, $800000
+	ld	e, b	; ld e, $FF
+	ret
+
+.maybe_subnormal:
+	add	hl, bc
+	inc	hl	; restore HL
+	jr	nc, .ret_zero
+	call	__ictlz
+	cpl
+	add	a, 130
+	jr	.int_to_float
+
+	extern	__ltof
+	extern	__ictlz
+	extern	___fe_cur_env
+	extern	_errno

test/floating_point/float32_ilogb/src/main.c

@@ -2,7 +2,9 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <string.h>
 #include <math.h>
+#include <fenv.h>
 #include <assert.h>
 #include <ti/screen.h>
 #include <ti/getcsc.h>
@@ -13,6 +15,24 @@
 
 #define ARRAY_LENGTH(x) (sizeof(x) / sizeof(x[0]))
 
+#if 0
+#define test_printf printf
+#else
+#define test_printf(...)
+#endif
+
+float truth_logbf(float x) {
+    if (isfinite(x)) {
+        if (iszero(x)) {
+            feraiseexcept(FE_DIVBYZERO);
+            return -HUGE_VALF;
+        }
+        return (float)ilogbf(x);
+    }
+    // infinity and NaN
+    return fabsf(x);
+}
+
 size_t run_test(void) {
     typedef float input_t;
     typedef int output_t;
@@ -24,9 +44,13 @@ size_t run_test(void) {
     for (size_t i = 0; i < length; i++) {
         int result = ilogbf(input[i]);
         if (result != output[i]) {
-            #if 0
-                printf("%3zu: %08lX\n\t%d != %d\n", i, input[i], result, output[i]);
-            #endif
+            test_printf("%3zu: %08lX\n%d != %d\n", i, input[i], result, output[i]);
+            return i;
+        }
+        float f_truth = truth_logbf(input[i]);
+        float f_guess = logbf(input[i]);
+        if (memcmp(&f_guess, &f_truth, sizeof(float)) != 0) {
+            test_printf("%3zu: %08lX %d\n%08lX != %08lX\n", i, input[i], output[i], f_guess, f_truth);
             return i;
         }
     }

test/floating_point/float64_ilogb/src/main.c

@@ -2,7 +2,9 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <string.h>
 #include <math.h>
+#include <fenv.h>
 #include <assert.h>
 #include <ti/screen.h>
 #include <ti/getcsc.h>
@@ -13,6 +15,24 @@
 
 #define ARRAY_LENGTH(x) (sizeof(x) / sizeof(x[0]))
 
+#if 0
+#define test_printf printf
+#else
+#define test_printf(...)
+#endif
+
+long double truth_logbl(long double x) {
+    if (isfinite(x)) {
+        if (iszero(x)) {
+            feraiseexcept(FE_DIVBYZERO);
+            return -HUGE_VALL;
+        }
+        return (long double)ilogbl(x);
+    }
+    // infinity and NaN
+    return fabsl(x);
+}
+
 size_t run_test(void) {
     typedef long double input_t;
     typedef int output_t;
@@ -24,9 +44,13 @@ size_t run_test(void) {
     for (size_t i = 0; i < length; i++) {
         int result = ilogbl(input[i]);
         if (result != output[i]) {
-            #if 0
-                printf("%4zu: %016llX\n %d != %d\n", i, input[i], result, output[i]);
-            #endif
+            test_printf("%4zu: %016llX\n%d != %d\n", i, input[i], result, output[i]);
+            return i;
+        }
+        long double f_truth = truth_logbl(input[i]);
+        long double f_guess = logbl(input[i]);
+        if (memcmp(&f_guess, &f_truth, sizeof(long double)) != 0) {
+            test_printf("%4zu:\n%016llX %d\n%016llX !=\n%016llX\n", i, input[i], output[i], f_guess, f_truth);
             return i;
         }
     }