Fix mantissa overflow bug

fuzzie360 · fuzzie360 · commit 13923a90d17e · 2016-03-05T12:44:32.000+08:00
diff --git a/src/backend/mode_gpu.js b/src/backend/mode_gpu.js
@@ -315,12 +315,16 @@
 					'	test += mantissa_part3 * exp2(exponent-7.0);',
 					'	test += mantissa_part2 * exp2(exponent-15.0);',
 					'	test += mantissa_part1 * exp2(exponent-23.0);',
-					'	float error = floor(log2(test) - log2F);',
-					'	if (abs(error) > 0.0) {',
-					'		exponent -= error;',
+					'	float error = log2(test) - log2F;',
+					'	if (abs(error) >= 1.0) {',
+					'		exponent -= floor(error);',
 					'		mantissa_part1 = integerMod(F * exp2(23.0-exponent), 256.0);',
 					'		mantissa_part2 = integerMod(F * exp2(15.0-exponent), 256.0);',
 					'		mantissa_part3 = integerMod(F * exp2(7.0-exponent), 128.0);',
+					'	} else if (abs(error) > 0.0) {',
+					'		mantissa_part1 = 0.0;',
+					'		mantissa_part2 = 0.0;',
+					'		mantissa_part3 = 0.0;',
 					'	}',
 					'	exponent += 127.0;',
 					'	vec4 rgba;',
