Hi,
Thanks for working on this issue. But this change is not clean. The change is
essentially assuming special semantics based on a variable name. What if a user
variable is named anon?
-Gautam
________________________________
From: Gang Yu <yugang...@gmail.com>
To: open64-devel <open64-devel@lists.sourceforge.net>
Sent: Thursday, April 19, 2012 2:01 AM
Subject: [Open64-devel] review request for fix bug965[WGEN]
Hi,
Could a gatekeeper please help review the fix for
bug965?(http://bugs.open64.net/show_bug.cgi?id=965)
This is a code-size issue for open64, i.e, the compiler generate garbage code
although it still make it right.
a cut-down case below:
static inline __attribute__((always_inline)) int
x86_this_cpu_constant_test_bit(unsigned int nr,
const unsigned long *addr)
{
unsigned long *a = (unsigned long *)addr + nr / 64;
return ((1UL << (nr % 64)) & ({ typeof(*a) pfo_ret__; switch (sizeof(*a)) {
case 1: asm("mov" "b ""%%""gs"":" "%P" "1"",%0" : "=q" (pfo_ret_\
_) : "m" (*a)); break; case 2: asm("mov" "w ""%%""gs"":" "%P" "1"",%0" : "=r"
(pfo_ret__) : "m" (*a)); break; case 4: asm("mov" "l ""%%""gs""\
:" "%P" "1"",%0" : "=r" (pfo_ret__) : "m" (*a)); break; case 8: asm("mov" "q
""%%""gs"":" "%P" "1"",%0" : "=r" (pfo_ret__) : "m" (*a)); break\
; default: __bad_percpu_size(); } pfo_ret__; })) != 0;
}
opencc -c anon.c -keep
yug@jupiter:~/work/codesize> readelf -s anon.o
Symbol table '.symtab' contains 8 entries:
Num: Value Size Type Bind Vis Ndx Name
4: 0000000000000000 8 OBJECT LOCAL DEFAULT 3 anon1
x86_this_cpu_constant_test_bit is non-called inline keyword function, so there
should generate nothing symbols in this object file, however, anon1 appears
unexpected.
Analysis:
When we examine the WGEN code, we found that the code snipper like these:
1569ST*
1570Create_ST_For_Tree (gs_t decl_node)
1571{
...
1609 else {
1610 sprintf(tempname, "anon%d", ++anon_count);
1611 name = tempname;
1612 }
...
1750 if (gs_tree_public (decl_node)) {
...
1776 else {
1777 sclass = SCLASS_FSTATIC;
1778 eclass = EXPORT_LOCAL;
1779 }
1780 level = GLOBAL_SYMTAB;
1781 }
this is to say, when current gs_tree is not public, we generate such a variable
as File-Scope(static) global variable.
However, anon1 appears as the temporary variable in a computation.
U8U8LDID 0 <2,4,pfo_ret__> T<9,.predef_U8,8>
U8STID 0 <1,51,anon1> T<9,.predef_U8,8> {line: 1/7}
U8INTCONST 1 (0x1)
I4I4LDID 0 <2,1,nr> T<4,.predef_I4,4>
I4INTCONST 63 (0x3f)
I4BAND
U8SHL
U8U8LDID 0 <1,51,anon1> T<9,.predef_U8,8>
U8BAND
U8INTCONST 0 (0x0)
I4U8NE
I4RETURN_VAL {line: 0/0}
and we do find the producer for anon
1609 else {
1610 sprintf(tempname, "anon%d", ++anon_count);
1611 name = tempname;
1612 }
we should make it SCLASS_AUTO in LOCAL_SYMTAB.
Suggested patch:
osprey/wgen/wgen_spin_symbol.cxx -- ff56fe0..b24a800 100644
--- a/osprey/wgen/wgen_spin_symbol.cxx
+++ b/osprey/wgen/wgen_spin_symbol.cxx
@@ -1774,10 +1774,18 @@ Create_ST_For_Tree (gs_t decl_node)
eclass = EXPORT_PREEMPTIBLE;
}
else {
+ if (name != tempname || strncmp(tempname,"anon",4)) {
sclass = SCLASS_FSTATIC;
eclass = EXPORT_LOCAL;
+ } else {
+ sclass = SCLASS_AUTO;
+ eclass = EXPORT_LOCAL;
+ }
}
- level = GLOBAL_SYMTAB;
+ if (name != tempname || strncmp(tempname,"anon",4))
+ level = GLOBAL_SYMTAB;
+ else
+ level = CURRENT_SYMTAB;
}
else {
#ifdef KEY
As an example, I show the codesize comparison to gcc generation and the source
code in the attach, we can see this is really bad for code-size.
Could a gatekeeper please help a review? thanks in advance.
Regards
Gang
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