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47833cff03
This addresses PR26055 LiveDebugValues is very slow.
Contrary to the old LiveDebugVariables pass LiveDebugValues currently
doesn't look at the lexical scopes before inserting a DBG_VALUE
intrinsic. This means that we often propagate DBG_VALUEs much further
down than necessary. This is especially noticeable in large C++
functions with many inlined method calls that all use the same
"this"-pointer.
For example, in the following code it makes no sense to propagate the
inlined variable a from the first inlined call to f() into any of the
subsequent basic blocks, because the variable will always be out of
scope:
void sink(int a);
void __attribute((always_inline)) f(int a) { sink(a); }
void foo(int i) {
f(i);
if (i)
f(i);
f(i);
}
This patch reuses the LexicalScopes infrastructure we have for
LiveDebugVariables to take this into account.
The effect on compile time and memory consumption is quite noticeable:
I tested a benchmark that is a large C++ source with an enormous
amount of inlined "this"-pointers that would previously eat >24GiB
(most of them for DBG_VALUE intrinsics) and whose compile time was
dominated by LiveDebugValues. With this patch applied the memory
consumption is 1GiB and 1.7% of the time is spent in LiveDebugValues.
https://reviews.llvm.org/D24994
Thanks to Daniel Berlin and Keith Walker for reviewing!
llvm-svn: 282611
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| Analysis | ||
| AsmParser | ||
| Bitcode | ||
| CodeGen | ||
| DebugInfo | ||
| Demangle | ||
| ExecutionEngine | ||
| Fuzzer | ||
| IR | ||
| IRReader | ||
| LibDriver | ||
| LineEditor | ||
| Linker | ||
| LTO | ||
| MC | ||
| Object | ||
| ObjectYAML | ||
| Option | ||
| Passes | ||
| ProfileData | ||
| Support | ||
| TableGen | ||
| Target | ||
| Transforms | ||
| CMakeLists.txt | ||
| LLVMBuild.txt | ||