shithub: dav1d

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msac: Avoid attempting to refill after eob has already been reached

Utilize the unsigned representation of a signed integer to skip
the refill code if the count was already negative to begin with,
which saves a few clock cycles at the end of each tile.

--- a/src/arm/64/msac.S

+++ b/src/arm/64/msac.S

@@ -216,7 +216,7 @@

         lsl             x7,  x7,  x5           // (~dif + (v << 48)) << d

         str             w4,  [x0, #RNG]

         mvn             x7,  x7                // ~dif

-        b.ge            9f

+        b.hs            9f

         // refill

         ldp             x3,  x4,  [x0]         // BUF_POS, BUF_END

--- a/src/x86/msac.asm

+++ b/src/x86/msac.asm

@@ -157,7 +157,7 @@

     mov [t7+msac.rng], t2d

     not            t4

     sub           t1d, ecx

-    jge .end ; no refill required

+    jae .end ; no refill required

 ; refill:

     mov            t2, [t7+msac.buf]

@@ -504,7 +504,7 @@

     mov [t7+msac.rng], t2d

     not            t4

     sub           t5d, ecx

-    jge %%end

+    jae %%end

     mov            t2, [t7+msac.buf]

     mov           rcx, [t7+msac.end]

 %if UNIX64 == 0