https://llvm.org/bugs/show_bug.cgi?id=23690
Bug ID: 23690
Summary: PGO for macro expansion code
Product: new-bugs
Version: 3.5
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
#define GET_BIT(lll) \
// blah blah
#define G(label1,label2) \
{ \
// decent amount code \
...
while (1) { \
GET_BIT(label2); \
}; \
}
void f() {
if (..)
G('c', 'd');
while ( .. )
G('a','b');
}
(This simplified case is from SPEC2006 401.bzip2 decompress.c)
After perf sampling, a lot of samples that should have landed in G and
GET_BIT is attributed to the two lines that have G expansion.
Discriminator does not work either for this case. However the last
field of DW_TAG_lexical_block ("Unique ID to identify blocks from a
template function") is unique for all instances of scopes in G and
GET_BIT. It will be great to have PGO get better profile of hot and
cold paths inside macros with nontrivial scopes.
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