round: Make fractional == 0.5 an unexpected branch

TimWolla · TimWolla · commit 865535267b7e · 2023-09-24T17:15:09.000+02:00
This does indeed result in slightly better assembly for clang.
diff --git a/ext/standard/math.c b/ext/standard/math.c
@@ -131,7 +131,7 @@ static inline double php_round_helper(double value, int mode) {
 				return integral + copysign(1.0, integral);
 			}
 
-			if (fractional == 0.5) {
+			if (UNEXPECTED(fractional == 0.5)) {
 				bool even = !fmod(integral, 2.0);
 
 				/* If the integral part is not even we can make it even
@@ -148,7 +148,7 @@ static inline double php_round_helper(double value, int mode) {
 				return integral + copysign(1.0, integral);
 			}
 
-			if (fractional == 0.5) {
+			if (UNEXPECTED(fractional == 0.5)) {
 				bool even = !fmod(integral, 2.0);
 
 				if (even) {

Original file line number	Diff line number	Diff line change
`@@ -131,7 +131,7 @@ static inline double php_round_helper(double value, int mode) {`
`131`	`131`	`return integral + copysign(1.0, integral);`
`132`	`132`	`}`
`133`	`133`
`134`		`- if (fractional == 0.5) {`
	`134`	`+ if (UNEXPECTED(fractional == 0.5)) {`
`135`	`135`	`bool even = !fmod(integral, 2.0);`
`136`	`136`
`137`	`137`	`/* If the integral part is not even we can make it even`
`@@ -148,7 +148,7 @@ static inline double php_round_helper(double value, int mode) {`
`148`	`148`	`return integral + copysign(1.0, integral);`
`149`	`149`	`}`
`150`	`150`
`151`		`- if (fractional == 0.5) {`
	`151`	`+ if (UNEXPECTED(fractional == 0.5)) {`
`152`	`152`	`bool even = !fmod(integral, 2.0);`
`153`	`153`
`154`	`154`	`if (even) {`