Matthew Dempsky bb192d1399 cmd/6c: Optimize rotate expressions to use rotate instructions. ... For simplicity, only recognizes expressions of the exact form "(x << a) | (x >> b)" where x is a variable and a and b are integer constant expressions that add to x's bit width. Fixes #4629. $ cat rotate.c unsigned int rotate(unsigned int x) { x = (x << 3) | (x >> (sizeof(x) * 8 - 3)); return x; } ## BEFORE $ go tool 6c -S rotate.c (rotate.c:2) TEXT rotate+0(SB),$0-8 (rotate.c:2) MOVL x+0(FP),!!DX (rotate.c:4) MOVL DX,!!AX (rotate.c:4) SALL $3,!!AX (rotate.c:4) MOVL DX,!!CX (rotate.c:4) SHRL $29,!!CX (rotate.c:4) ORL CX,!!AX (rotate.c:5) RET ,!! (rotate.c:5) RET ,!! (rotate.c:5) END ,!! ## AFTER $ go tool 6c -S rotate.c (rotate.c:2) TEXT rotate+0(SB),$0-8 (rotate.c:4) MOVL x+0(FP),!!AX (rotate.c:4) ROLL $3,!!AX (rotate.c:5) RET ,!! (rotate.c:5) RET ,!! (rotate.c:5) END ,!! R=rsc, minux.ma CC=golang-dev https://golang.org/cl/7069056		2013-01-18 17:29:53 -05:00
..
cgen.c	cmd/6c: Optimize rotate expressions to use rotate instructions.	2013-01-18 17:29:53 -05:00
div.c	various: avoid %ld etc	2010-10-13 16:20:22 -04:00
doc.go	cmd/5a, cmd/5c, cmd/6a, cmd/6c, cmd/8a, cmd/8c, cmd/ld: update reference	2013-01-18 13:39:53 -08:00
gc.h	cmd/{5g,6g,8g,6c}: remove unused macro, use %E to print etype.	2012-09-24 23:44:00 +02:00
list.c	cmd/6c, cmd/8c: add fixjmp step to regopt.	2012-12-06 07:20:03 +01:00
machcap.c	move 6c/pgen.c, 6c/pswt.c into cc	2009-07-07 10:07:15 -07:00
Makefile	build: delete make paraphernalia	2012-02-06 13:34:25 -05:00
mul.c	cmd/6c, cmd/8c: use signed char explicitly in mul.c	2012-11-09 21:06:45 +01:00
peep.c	cmd/6c: Improve peep hole optimization of rotate and shift instructions.	2013-01-18 16:33:25 -05:00
reg.c	cmd/6c, cmd/8c: add fixjmp step to regopt.	2012-12-06 07:20:03 +01:00
sgen.c	amd64: use segment memory for thread-local storage	2010-08-04 17:50:22 -07:00
swt.c	cmd/cgo, cmd/cc, cmd/ld: detect dynamic linker automatically	2012-05-05 01:54:16 +08:00
txt.c	cmd/6c: Optimize rotate expressions to use rotate instructions.	2013-01-18 17:29:53 -05:00