Looks good to me. Please go ahead.
2012/4/24 Gang Yu <yugang...@gmail.com>
> Hi,
>
> could a gatekeeper please help review the fix for bug963?(
> https://bugs.open64.net/show_bug.cgi?id=963)
>
> bug case:
> static inline __attribute__((always_inline)) __attribute__((pure)) unsigned
> char __static_cpu_has(unsigned short bit)
> {
> unsigned char flag;
>
> asm volatile("1: movb $0,%0\n"
> "2:\n"
> ".section .altinstructions,\"a\"\n"
> " " ".balign 8" " " "\n"
> " " ".quad" " " "1b\n"
> " " ".quad" " " "3f\n"
> " .word %P1\n"
> " .byte 2b - 1b\n"
> " .byte 4f - 3f\n"
> ".previous\n"
> ".section .discard,\"aw\",@progbits\n"
> " .byte 0xff + (4f-3f) - (2b-1b)\n"
> ".previous\n"
> ".section .altinstr_replacement,\"ax\"\n"
> "3: movb $1,%0\n"
> "4:\n"
> ".previous\n"
> : "=qm" (flag) : "i" (bit));
> return flag;
>
> }
>
> unsigned char f(void){
> return __static_cpu_has(24) ;
> }
>
> opencc -c bug963 <https://bugs.open64.net/show_bug.cgi?id=963>.c -O2
> "bug963 <https://bugs.open64.net/show_bug.cgi?id=963>.c", line 5: Error:
> Invalid 'asm' constrain : Cannot find immediate
> operand for ASM
>
> Analysis:
>
> 24 is a constant value for bit in the caller, when __static_cpu_has is
> inlined to f, the bit value is failed to copy propagated into the
> ASM_INPUT, this is because we now only enable var->var copy propagation for
> ASM_INPUT, for the case of "i" constraint, we need do such cprop.
>
> gcc internals
> (http://gcc.gnu.org/onlinedocs/gccint/Simple-Constraints.html)
> documents the "i" constraint as below, it is a target-independent
> constraint.
>
> `i' An immediate integer operand (one with constant value) is allowed.
> This includes symbolic constants whose values will be known only at
> assembly time or later.
>
> suggested patch:
> osprey/be/opt/opt_prop.cxx -- 966f38e..8cc897c 100644
> --- a/osprey/be/opt/opt_prop.cxx
> +++ b/osprey/be/opt/opt_prop.cxx
> @@ -1511,6 +1511,14 @@ COPYPROP::Copy_propagate_cr(CODEREP *x, BB_NODE
> *curbb,
> CODEREP *possible_prop = Copy_propagate_cr(x->Opnd(i),
> curbb, inside_cse, in_array);
> if (possible_prop && possible_prop->Kind() ==
> x->Opnd(i)->Kind())
> expr = possible_prop;
> + // open64.net bug963. If the Asm_input constraint is "i",
> i.e, required immediate
> + // and the possible propagation is also a var, we do this
> propagation on demand.
> + else if (possible_prop &&
> + (possible_prop->Kind() == CK_CONST ||
> + possible_prop->Kind() == CK_RCONST) &&
> +
> !strncmp(ST_name(&St_Table[x->Asm_constraint()]),"i",1)) {
> + expr = possible_prop;
> + }
> else {
> x->Opnd(i)->Set_flag(CF_DONT_PROP);
> expr = NULL;
> Could a gatekeeper please help a review? thanks in advance.
>
>
> Regards
> Gang
>
>
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>
--
Regards,
Lai Jian-Xin
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