Re: How to make IRA not to move an instruction

[Jeff Law]

On 05/28/10 10:38, H.J. Lu wrote:
Hi,
I want to generate vzeroupper when I know upper 128bits aren't used. I
can't find
a way to mark an pattern which zeros upper 128bits. So I added
   
Presumably you can't use a zero_extract?

[ ... ]

before IRA,

(insn 2 4 3 2 x.i:9 (set (reg/v:V8SF 59 [ y ])
         (reg:V8SF 21 xmm0 [ y ])) 1036 {*avx_movv8sf_internal}
(expr_list:REG_DEAD (reg:V8SF 21 xmm0 [ y ])
         (nil)))

(note 3 2 6 2 NOTE_INSN_FUNCTION_BEG)

(insn 6 3 7 2 x.i:10 (unspec_volatile [
             (const_int 0 [0])
         ] 17) 1960 {avx_vzeroupper_nop} (nil))

(call_insn 7 6 8 2 x.i:10 (call (mem:QI (symbol_ref:DI ("bar2") [flags
0x41]<function_decl 0x7ffa930ecd00 bar2>) [0 S1 A8])
         (const_int 0 [0])) 599 {*call_0} (nil)
     (nil))


after IRA,

(insn 6 3 20 2 x.i:10 (unspec_volatile [
             (const_int 0 [0])
         ] 17) 1960 {avx_vzeroupper_nop} (nil))

(insn 20 6 7 2 x.i:10 (set (mem/c:V8SF (reg/f:DI 7 sp) [3 S32 A256])
         (reg:V8SF 21 xmm0)) 1036 {*avx_movv8sf_internal} (nil))

(call_insn 7 20 21 2 x.i:10 (call (mem:QI (symbol_ref:DI ("bar2")
[flags 0x41]<function_decl 0x7ffa930ecd00 bar2>) [0 S1 A8])
         (const_int 0 [0])) 599 {*call_0} (nil)
     (nil))

Since vzeroupper will change xmm0/ymm0, the value saved on stack is wrong.
Is that a way to tell IRA not to move an instruction?
   
You need to expose those operands so that the dataflow information is 
correct.

jeff