[PATCH] Better __ashlDI3, __ashrDI3 and __lshrDI3 functions, plus fixed __bswapsi2 function

["Stefan Kanthak" <stefan.kanthak@nexgo.de>]

[-- Attachment #1: Type: text/plain, Size: 381 bytes --]

The implementation of the __ashlDI3(), __ashrDI3() and __lshrDI3() functions
is rather bad, it yields bad machine code at least on i386 and AMD64.
Since GCC knows how to shift integers twice the register size these functions
can be written as one-liners.

The implementation of the __bswapsi2() function uses SIGNED instead of
unsigned mask values; cf. __bswapdi2()

Stefan Kanthak

[-- Attachment #2: libgcc2.diff --]
[-- Type: application/octet-stream, Size: 2702 bytes --]

--- -/libgcc/libgcc2.h
+++ +/libgcc/libgcc2.h
@@ -391,7 +391,7 @@
 extern DWtype __negdi2 (DWtype);
 #endif
 
-extern DWtype __lshrdi3 (DWtype, shift_count_type);
+extern UDWtype __lshrdi3 (UDWtype, shift_count_type);
 extern DWtype __ashldi3 (DWtype, shift_count_type);
 extern DWtype __ashrdi3 (DWtype, shift_count_type);
 
--- -/libgcc/libgcc2.c
+++ +/libgcc/libgcc2.c
@@ -398,30 +398,10 @@
 /* Unless shift functions are defined with full ANSI prototypes,
    parameter b will be promoted to int if shift_count_type is smaller than an int.  */
 #ifdef L_lshrdi3
-DWtype
-__lshrdi3 (DWtype u, shift_count_type b)
+UDWtype
+__lshrdi3 (UDWtype u, shift_count_type b)
 {
-  if (b == 0)
-    return u;
-
-  const DWunion uu = {.ll = u};
-  const shift_count_type bm = W_TYPE_SIZE - b;
-  DWunion w;
-
-  if (bm <= 0)
-    {
-      w.s.high = 0;
-      w.s.low = (UWtype) uu.s.high >> -bm;
-    }
-  else
-    {
-      const UWtype carries = (UWtype) uu.s.high << bm;
-
-      w.s.high = (UWtype) uu.s.high >> b;
-      w.s.low = ((UWtype) uu.s.low >> b) | carries;
-    }
-
-  return w.ll;
+  return u >> b;
 }
 #endif
 
@@ -429,27 +409,7 @@
 DWtype
 __ashldi3 (DWtype u, shift_count_type b)
 {
-  if (b == 0)
-    return u;
-
-  const DWunion uu = {.ll = u};
-  const shift_count_type bm = W_TYPE_SIZE - b;
-  DWunion w;
-
-  if (bm <= 0)
-    {
-      w.s.low = 0;
-      w.s.high = (UWtype) uu.s.low << -bm;
-    }
-  else
-    {
-      const UWtype carries = (UWtype) uu.s.low >> bm;
-
-      w.s.low = (UWtype) uu.s.low << b;
-      w.s.high = ((UWtype) uu.s.high << b) | carries;
-    }
-
-  return w.ll;
+  return u << b;
 }
 #endif
 
@@ -457,28 +417,7 @@
 DWtype
 __ashrdi3 (DWtype u, shift_count_type b)
 {
-  if (b == 0)
-    return u;
-
-  const DWunion uu = {.ll = u};
-  const shift_count_type bm = W_TYPE_SIZE - b;
-  DWunion w;
-
-  if (bm <= 0)
-    {
-      /* w.s.high = 1..1 or 0..0 */
-      w.s.high = uu.s.high >> (W_TYPE_SIZE - 1);
-      w.s.low = uu.s.high >> -bm;
-    }
-  else
-    {
-      const UWtype carries = (UWtype) uu.s.high << bm;
-
-      w.s.high = uu.s.high >> b;
-      w.s.low = ((UWtype) uu.s.low >> b) | carries;
-    }
-
-  return w.ll;
+  return u >> b;
 }
 #endif
 \f
@@ -486,10 +425,10 @@
 SItype
 __bswapsi2 (SItype u)
 {
-  return ((((u) & 0xff000000) >> 24)
-	  | (((u) & 0x00ff0000) >>  8)
-	  | (((u) & 0x0000ff00) <<  8)
-	  | (((u) & 0x000000ff) << 24));
+  return ((((u) & 0xff000000u) >> 24)
+	  | (((u) & 0x00ff0000u) >>  8)
+	  | (((u) & 0x0000ff00u) <<  8)
+	  | (((u) & 0x000000ffu) << 24));
 }
 #endif
 #ifdef L_bswapdi2