improve performance for number to string conversion functions (#28661)

* improve performance for number to string conversion functions

base/intfuncs.jl

@@ -543,35 +543,35 @@ function bin(x::Unsigned, pad::Int, neg::Bool)
     i = neg + max(pad,sizeof(x)<<3-leading_zeros(x))
     a = StringVector(i)
     while i > neg
-        a[i] = '0'+(x&0x1)
+        @inbounds a[i] = 48+(x&0x1)
         x >>= 1
         i -= 1
     end
-    if neg; a[1]='-'; end
+    if neg; @inbounds a[1]=0x2d; end
     String(a)
 end
 
 function oct(x::Unsigned, pad::Int, neg::Bool)
     i = neg + max(pad,div((sizeof(x)<<3)-leading_zeros(x)+2,3))
     a = StringVector(i)
     while i > neg
-        a[i] = '0'+(x&0x7)
+        @inbounds a[i] = 48+(x&0x7)
         x >>= 3
         i -= 1
     end
-    if neg; a[1]='-'; end
+    if neg; @inbounds a[1]=0x2d; end
     String(a)
 end
 
 function dec(x::Unsigned, pad::Int, neg::Bool)
     i = neg + ndigits(x, base=10, pad=pad)
     a = StringVector(i)
     while i > neg
-        a[i] = '0'+rem(x,10)
+        @inbounds a[i] = 48+rem(x,10)
         x = oftype(x,div(x,10))
         i -= 1
     end
-    if neg; a[1]='-'; end
+    if neg; @inbounds a[1]=0x2d; end
     String(a)
 end
 
@@ -580,11 +580,11 @@ function hex(x::Unsigned, pad::Int, neg::Bool)
     a = StringVector(i)
     while i > neg
         d = x & 0xf
-        a[i] = '0'+d+39*(d>9)
+        @inbounds a[i] = 48+d+39*(d>9)
         x >>= 4
         i -= 1
     end
-    if neg; a[1]='-'; end
+    if neg; @inbounds a[1]=0x2d; end
     String(a)
 end