cyb70289 commented on a change in pull request #10859:
URL: https://github.com/apache/arrow/pull/10859#discussion_r681592003
##########
File path: cpp/src/arrow/csv/chunker.cc
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@@ -63,12 +63,18 @@ class Lexer {
case IN_FIELD:
goto InField;
case AT_ESCAPE:
+ // will never reach here if escaping = false
+ // just to hint the compiler to remove dead code
+ if (!escaping) return nullptr;
goto AtEscape;
case IN_QUOTED_FIELD:
+ if (!quoting) return nullptr;
goto InQuotedField;
Review comment:
The way I validate above assumption is a bit rough.
I added below code snippet after
[InQuotedField](https://github.com/apache/arrow/blob/de7cc1e4820e96531aae3b7f3fc9105f7b3a5f3a/cpp/src/arrow/csv/chunker.cc#L124)
```
InQuotedField:
if (!quoting) {
__asm volatile ("pause" ::: "memory");
__asm volatile ("pause" ::: "memory");
__asm volatile ("pause" ::: "memory");
}
```
Logically, these three "pause" instruction should not be available.
Without this patch, I can find the three continuous pause in disassembled
libarrow.so. With this patch, they are gone.
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