cmov: XOR within the ASM block (#925)

RustCrypto · Oct 3, 2023 · 582883a · 582883a
1 parent 895b4a5
commit 582883a
Showing 1 changed file with 66 additions and 6 deletions.
diff --git a/cmov/src/x86.rs b/cmov/src/x86.rs
@@ -25,6 +25,24 @@ macro_rules! cmov {
     };
 }
 
+macro_rules! cmov_eq {
+    ($xor:expr, $instruction:expr, $lhs:expr, $rhs:expr, $condition:expr, $dst:expr) => {
+        let mut tmp = *$dst as u16;
+        unsafe {
+            asm! {
+                $xor,
+                $instruction,
+                inout(reg) *$lhs => _,
+                in(reg) *$rhs,
+                inlateout(reg) tmp,
+                in(reg) $condition as u16,
+                options(pure, nomem, nostack),
+            };
+        }
+        *$dst = tmp as u8;
+    };
+}
+
 impl Cmov for u16 {
     #[inline]
     fn cmovnz(&mut self, value: &Self, condition: Condition) {
@@ -40,12 +58,26 @@ impl Cmov for u16 {
 impl CmovEq for u16 {
     #[inline]
     fn cmoveq(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:x}, {1:x}",
+            "cmovz {2:e}, {3:e}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 
     #[inline]
     fn cmovne(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovnz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:x}, {1:x}",
+            "cmovnz {2:e}, {3:e}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 }
 
@@ -64,12 +96,26 @@ impl Cmov for u32 {
 impl CmovEq for u32 {
     #[inline]
     fn cmoveq(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:e}, {1:e}",
+            "cmovz {2:e}, {3:e}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 
     #[inline]
     fn cmovne(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovnz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:e}, {1:e}",
+            "cmovnz {2:e}, {3:e}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 }
 
@@ -140,11 +186,25 @@ impl Cmov for u64 {
 impl CmovEq for u64 {
     #[inline]
     fn cmoveq(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:r}, {1:r}",
+            "cmovz {2:r}, {3:r}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 
     #[inline]
     fn cmovne(&self, rhs: &Self, input: Condition, output: &mut Condition) {
-        output.cmovnz(&input, (self ^ rhs) as u8);
+        cmov_eq!(
+            "xor {0:r}, {1:r}",
+            "cmovnz {2:r}, {3:r}",
+            self,
+            rhs,
+            input,
+            output
+        );
     }
 }