perf: use Arguments::as_str to bypass the formatting mechanism if p…

…ossible This involves branching, but as shown in [1], the compiler seems to have no problem resolving the branch at compile time if optimization is enabled. [1]: rust-lang/rust#74056 (comment)
r3-os · Mar 22, 2022 · dc45afb · dc45afb
1 parent aa79a7c
commit dc45afb
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Showing 3 changed files with 32 additions and 8 deletions.
diff --git a/src/arm_semihosting/src/macros.rs b/src/arm_semihosting/src/macros.rs
@@ -35,7 +35,13 @@ macro_rules! syscall1 {
 #[macro_export]
 macro_rules! hprint {
     ($($tt:tt)*) => {
-        $crate::export::hstdout_fmt(format_args!($($tt)*))
+        match ::core::format_args!($($tt)*) {
+            args => if let ::core::option::Option::Some(s) = args.as_str() {
+                $crate::export::hstdout_str(s)
+            } else {
+                $crate::export::hstdout_fmt(args)
+            },
+        }
     };
 }
 
@@ -45,7 +51,7 @@ macro_rules! hprint {
 #[macro_export]
 macro_rules! hprintln {
     ($($tt:tt)*) => {
-        match $crate::export::hstdout_fmt(format_args!($($tt)*)) {
+        match $crate::hprint!($($tt)*) {
             Ok(()) => $crate::export::hstdout_str("\n"),
             Err(()) => Err(()),
         }
@@ -58,7 +64,13 @@ macro_rules! hprintln {
 #[macro_export]
 macro_rules! heprint {
     ($($tt:tt)*) => {
-        $crate::export::hstderr_fmt(format_args!($($tt)*))
+        match ::core::format_args!($($tt)*) {
+            args => if let ::core::option::Option::Some(s) = args.as_str() {
+                $crate::export::hstderr_str(s)
+            } else {
+                $crate::export::hstderr_fmt(args)
+            },
+        }
     };
 }
 
@@ -68,7 +80,7 @@ macro_rules! heprint {
 #[macro_export]
 macro_rules! heprintln {
     ($($tt:tt)*) => {
-        match $crate::export::hstderr_fmt(format_args!($($tt)*)) {
+        match $crate::heprint!($($tt)*) {
             Ok(()) => $crate::export::hstderr_str("\n"),
             Err(()) => Err(()),
         }

diff --git a/src/r3_support_rp2040/src/stdout.rs b/src/r3_support_rp2040/src/stdout.rs
@@ -106,15 +106,21 @@ pub fn write_fmt(args: fmt::Arguments<'_>) {
 #[macro_export]
 macro_rules! sprint {
     ($($tt:tt)*) => {
-        $crate::stdout::write_fmt(format_args!($($tt)*))
+        match ::core::format_args!($($tt)*) {
+            args => if let ::core::option::Option::Some(s) = args.as_str() {
+                $crate::stdout::write_str(s)
+            } else {
+                $crate::stdout::write_fmt(args)
+            },
+        }
     };
 }
 
 /// Macro for printing to the serial standard output, with a newline.
 #[macro_export]
 macro_rules! sprintln {
     ($($tt:tt)*) => {{
-        $crate::stdout::write_fmt(format_args!($($tt)*));
+        $crate::sprint!($($tt)*);
         $crate::stdout::write_str("\n");
     }};
 }
diff --git a/src/r3_support_rza1/src/stdout.rs b/src/r3_support_rza1/src/stdout.rs
@@ -102,15 +102,21 @@ pub fn write_fmt(args: fmt::Arguments<'_>) {
 #[macro_export]
 macro_rules! sprint {
     ($($tt:tt)*) => {
-        $crate::stdout::write_fmt(format_args!($($tt)*))
+        match ::core::format_args!($($tt)*) {
+            args => if let ::core::option::Option::Some(s) = args.as_str() {
+                $crate::stdout::write_str(s)
+            } else {
+                $crate::stdout::write_fmt(args)
+            },
+        }
     };
 }
 
 /// Macro for printing to the serial standard output, with a newline.
 #[macro_export]
 macro_rules! sprintln {
     ($($tt:tt)*) => {{
-        $crate::stdout::write_fmt(format_args!($($tt)*));
+        $crate::sprint!($($tt)*);
         $crate::stdout::write_str("\n");
     }};
 }