Hi, All Can gatekeeper help review this patch?
For attached test case, in foo, *p reference is not alias with a in nystrom
alias analysis.
The problem is when creating alias tag, alias_tag points to blackhole is not
updated correctly.
Alias dump before fix.
I4INTCONST 2 (0x2) {cgnode 1}
I4STID 0 <1,51,a> T<4,.predef_I4,4> {line: 1/5} {cgnode 3}
I4INTCONST 3 (0x3) {cgnode 1}
U8U8LDID 0 <1,52,p> T<53,anon_ptr.,8> {cgnode 4}
I4ISTORE 0 T<53,anon_ptr.,8> {line: 1/6} {cgnode 4} {alias_tag 2}
I4I4LDID 0 <1,51,a> T<4,.predef_I4,4> {cgnode 3}
I4STID 1 <1,5,.preg_I8> T<4,.predef_I4,4> # $r1 {line: 1/7} {cgnode 5}
RETURN {line: 1/7}
store to p's alias_tag 2 only points to black hole cg node.
It will not alias with STID a (alias_tag 3), because alias_tag 2 not points
to cg node 3.
Dump result for alias tag.
alias tag 2: points to cg nodes [2] // black hole
alias tag 3: points to cg nodes [3] // a
alias tag 5: points to cg nodes [4] // p
Fix is,
For non-ipa alias analysis, if alias tag points to black hole, make it
points to all global and escaple local.
If ipa can't find the points to, its a ipa analysis bug.
after fix
alias tag 2: points to cg nodes [2, 3, 4] // points to blackhole, a and p.
alias tag 3: points to cg nodes [3]
alias tag 4: points to cg nodes [2, 3, 4]
alias tag 5: points to cg nodes [4]
Regards
Shi Hui
blackhole.patch
Description: Binary data
int *p;
int a;
int foo()
{
a = 2;
*p = 3;
return a;
}
int main()
{
p = &a;
return foo();
}
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