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cmd/internal/obj/arm64: optimize constant pool 

"MOVD $0xaaaaaaaa, R2"
"MOVD $-0x55555555, R3"

For the above instructions, 64-bit constants 0x00000000 aaaaaaaa
and 0xffffffff aaaaaaab are stored in the constant pool.

This CL optimizes them to
"MOVWU $0xaaaaaaaa, R2"
"MOVW $-0x05555555, R3"
and 32-bit constants 0xaaaaaaaa and 0xaaaaaaab are stored in the
constant pool.

There is a little size reduction (about total 5KB) in both the go
executable and the library files.

Change-Id: I7c4bfa6cd9c07da99c69a8f9c15010a0cce3b735
Reviewed-on: https://go-review.googlesource.com/105775
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Ben Shi 2018-04-09 11:12:15 +00:00 committed by Cherry Zhang
parent c1ed1f3c80
commit 9be1921042
1 changed files with 16 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
src/cmd/internal/obj/arm64/asm7.go
View File

@ -933,6 +933,11 @@ func (c *ctxt7) flushpool(p *obj.Prog, skip int) {
}
/*
* MOVD foo(SB), R is actually
* MOVD addr, REGTMP
* MOVD REGTMP, R
* where addr is the address of the DWORD containing the address of foo.
*
* TODO: hash
*/
func (c *ctxt7) addpool(p *obj.Prog, a *obj.Addr) {
@ -942,11 +947,17 @@ func (c *ctxt7) addpool(p *obj.Prog, a *obj.Addr) {
t.As = AWORD
sz := 4
// MOVD foo(SB), R is actually
// MOVD addr, REGTMP
// MOVD REGTMP, R
// where addr is the address of the DWORD containing the address of foo.
if p.As == AMOVD && a.Type != obj.TYPE_MEM || cls == C_ADDR || cls == C_VCON || lit != int64(int32(lit)) || uint64(lit) != uint64(uint32(lit)) {
if p.As == AMOVD && a.Type == obj.TYPE_CONST {
// simplify MOVD to MOVW/MOVWU to reduce constant pool size
if lit == int64(int32(lit)) { // -0x80000000 ~ 0x7fffffff
p.As = AMOVW
} else if uint64(lit) == uint64(uint32(lit)) { // 0 ~ 0xffffffff
p.As = AMOVWU
} else { // 64-bit
t.As = ADWORD
sz = 8
}
} else if p.As == AMOVD && a.Type != obj.TYPE_MEM || cls == C_ADDR || cls == C_VCON || lit != int64(int32(lit)) || uint64(lit) != uint64(uint32(lit)) {
// conservative: don't know if we want signed or unsigned extension.
// in case of ambiguity, store 64-bit
t.As = ADWORD