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* patch by Nico Erfurth: Optimize SwapEndian for ARM

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The new version uses a pure pascal version for the 32bit case.
With the lastest compiler optimizations this generates optimal
4-instruction code which can be inlined. The rev-versions for
armv6+ are gone now, the inlineable pascal-code is faster than
the call-overhead for the rev-implementation.

The 64-bit versions received an updated assembly version which saves 4
cycles total on <armv6.

git-svn-id: trunk@21511 -
This commit is contained in:
florian 2012-06-06 19:46:06 +00:00
parent 45c70ec81c
commit 2a2a1e5788
1 changed files with 36 additions and 68 deletions
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104
rtl/arm/arm.inc
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@ -892,88 +892,56 @@ end;
*)
function SwapEndian(const AValue: LongInt): LongInt;assembler;nostackframe;
asm
// We're starting with r0 = 4321
{$if defined(cpuarmv3) or defined(cpuarmv4) or defined(cpuarmv5)}
mov r2, r0, lsr #24 // r2 = 0004
and r1, r0, #16711680 // r1 = 0300
orr r2, r2, r0, lsl #24 // r2 = 1004
orr r2, r2, r1, lsr #8 // r2 = 1034
and r0, r0, #65280 // r0 = 0020
orr r0, r2, r0, lsl #8 // r0 = 1234
{$else}
rev r0, r0
{$endif}
{
These used to be an assembler-function, but with newer improvements to the compiler this
generates a perfect 4 cycle code sequence and can be inlined.
}
function SwapEndian(const AValue: LongWord): LongWord;{$ifdef SYSTEMINLINE}inline;{$endif}
begin
Result:= AValue xor rordword(AValue,16);
Result:= Result and $FF00FFFF;
Result:= (Result shr 8) xor rordword(AValue,8);
end;
function SwapEndian(const AValue: DWord): DWord;assembler;nostackframe;
asm
// We're starting with r0 = 4321
{$if defined(cpuarmv3) or defined(cpuarmv4) or defined(cpuarmv5)}
mov r2, r0, lsr #24 // r2 = 0004
and r1, r0, #16711680 // r1 = 0300
orr r2, r2, r0, lsl #24 // r2 = 1004
orr r2, r2, r1, lsr #8 // r2 = 1034
and r0, r0, #65280 // r0 = 0020
orr r0, r2, r0, lsl #8 // r0 = 1234
{$else}
rev r0, r0
{$endif}
function SwapEndian(const AValue: LongInt): LongInt;{$ifdef SYSTEMINLINE}inline;{$endif}
begin
Result:=LongInt(SwapEndian(DWord(AValue)));
end;
{
Currently freepascal will not generate a good assembler sequence for
Result:=(SwapEndian(longword(lo(AValue))) shl 32) or
(SwapEndian(longword(hi(AValue))));
So we keep an assembly version for now
}
function SwapEndian(const AValue: Int64): Int64; assembler; nostackframe;
asm
// We're starting with r0 = 4321 r1 = 8765
{$if defined(cpuarmv3) or defined(cpuarmv4) or defined(cpuarmv5)}
mov ip, r1
mov r2, r0, lsr #24 // r2 = 0004
and r3, r0, #16711680 // r3 = 0300
orr r2, r2, r0, lsl #24 // r2 = 1004
orr r2, r2, r3, lsr #8 // r2 = 1034
and r0, r0, #65280 // r0 = 0020
orr r1, r2, r0, lsl #8 // r1 = 1234
// We're starting with r0 = $87654321
eor r1, r0, r0, ror #16 // r1 = $C444C444
bic r1, r1, #16711680 // r1 = r1 and $ff00ffff = $C400C444
mov r0, r0, ror #8 // r0 = $21876543
eor r1, r0, r1, lsr #8 // r1 = $21436587
eor r0, ip, ip, ror #16
bic r0, r0, #16711680
mov ip, ip, ror #8
eor r0, ip, r0, lsr #8
mov r2, ip, lsr #24 // r2 = 0008
and r3, ip, #16711680 // r1 = 0700
orr r2, r2, ip, lsl #24 // r2 = 5008
orr r2, r2, r3, lsr #8 // r2 = 5078
and ip, ip, #65280 // ip = 0060
orr r0, r2, ip, lsl #8 // r0 = 5678
bx lr
{$else}
rev r2, r0
rev r0, r1
mov r1, r2
rev r2, r0
rev r0, r1
mov r1, r2
{$endif}
end;
function SwapEndian(const AValue: QWord): QWord; assembler; nostackframe;
asm
// We're starting with r0 = 4321 r1 = 8765
{$if defined(cpuarmv3) or defined(cpuarmv4) or defined(cpuarmv5)}
mov ip, r1
mov r2, r0, lsr #24 // r2 = 0004
and r3, r0, #16711680 // r3 = 0300
orr r2, r2, r0, lsl #24 // r2 = 1004
orr r2, r2, r3, lsr #8 // r2 = 1034
and r0, r0, #65280 // r0 = 0020
orr r1, r2, r0, lsl #8 // r1 = 1234
mov r2, ip, lsr #24 // r2 = 0008
and r3, ip, #16711680 // r1 = 0700
orr r2, r2, ip, lsl #24 // r2 = 5008
orr r2, r2, r3, lsr #8 // r2 = 5078
and ip, ip, #65280 // ip = 0060
orr r0, r2, ip, lsl #8 // r0 = 5678
bx lr
{$else}
rev r2, r0
rev r0, r1
mov r1, r2
{$endif}
function SwapEndian(const AValue: QWord): QWord; {$ifdef SYSTEMINLINE}inline;{$endif}
begin
Result:=QWord(SwapEndian(Int64(AValue)));
end;
{include hand-optimized assembler division code}