[llvm-commits] [compiler-rt] r107555 - in /compiler-rt/trunk/lib/arm: bswapdi2.S bswapsi2.S

[John Tytgat]

In message <20100703010049.D01E92A6C12C at llvm.org>
          Stephen Canon <scanon at apple.com> wrote:

> Author: scanon
> Date: Fri Jul  2 20:00:49 2010
> New Revision: 107555
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=107555&view=rev
> Log:
> Marginally smaller implementations of bswap for ARMv4, ARMv5 that avoid the need to establish a frame
> 
> Modified:
>     compiler-rt/trunk/lib/arm/bswapdi2.S
>     compiler-rt/trunk/lib/arm/bswapsi2.S

This can be further optimised using a well known endian swap 4 instruction
idiom.  Patch attached.

John.
-- 
John Tytgat
John at bass-software.com
-------------- next part --------------
Index: bswapdi2.S
===================================================================
--- bswapdi2.S	(revision 107570)
+++ bswapdi2.S	(working copy)
@@ -14,25 +14,23 @@
 //
 // Reverse all the bytes in a 64-bit integer.
 //
-    .align 2
+	.align 2
 DEFINE_COMPILERRT_FUNCTION(__bswapdi2)
 #if __ARM_ARCH_5TEJ__ || __ARM_ARCH_4T__
-    mov r12, #0xff00
-    
-    and r3,  r12, r0, lsr #8
-    and r2,  r12, r0    
-    orr r3,   r3, r0, lsr #24   
-    orr r3,   r3, r0, lsl #24
-    orr r2,   r3, r2, lsl #8  // r2 = rev(r0)
-    
-    and r3,  r12, r1, lsr #8
-    and r0,  r12, r1
-    orr r3,   r3, r1, lsr #24
-    orr r3,   r3, r1, lsl #24
-    orr r0,   r3, r0, lsl #8  // r0 = rev(r1)
+	eor	r2, r0, r0, ror #16
+	bic	r2, r2, #0xff0000
+	mov	r2, r2, lsr #8
+	eor	r2, r2, r0, ror #8
+
+	eor	r0, r1, r1, ror #16
+	bic	r0, r0, #0xff0000
+	mov	r0, r0, lsr #8
+	eor	r0, r0, r1, ror #8
+
+	mov	r1, r2
 #else
-    rev r2,   r0  // r2 = rev(r0)
-    rev r0,   r1  // r0 = rev(r1)
+	rev r2,   r0  // r2 = rev(r0)
+	rev r0,   r1  // r0 = rev(r1)
 #endif
-    mov r1,   r2  // r1 = r2 = rev(r0)
-    bx  lr
+	mov r1,   r2  // r1 = r2 = rev(r0)
+	bx  lr
Index: bswapsi2.S
===================================================================
--- bswapsi2.S	(revision 107570)
+++ bswapsi2.S	(working copy)
@@ -18,12 +18,10 @@
 DEFINE_COMPILERRT_FUNCTION(__bswapsi2)
 #if __ARM_ARCH_5TEJ__ || __ARM_ARCH_4T__
 	// before armv6 does not have "rev" instruction
-    mov r1, #0xff00
-    and r2, r1, r0, lsr #8 
-    and r1, r1, r0   
-    orr r2, r2, r0, lsr #24
-    orr r2, r2, r0, lsl #24
-    orr r0, r2, r1, lsl #8
+	eor	r1, r0, r0, ror #16
+	bic	r1, r1, #0xff0000
+	mov	r1, r1, lsr #8
+	eor	r0, r1, r0, ror #8
 #else
 	rev	r0, r0		// reverse bytes in parameter and put into result register
 #endif