http://llvm.org/bugs/show_bug.cgi?id=22020
Bug ID: 22020
Summary: Form a switch from a loop if the loop is really
switch-like
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Loop Optimizer
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
consider:
int f(char C) {
const char *Str = ",/\\:. \n\t\'-";
for (int i = 0, e = 10; i < e; ++i) {
if (Str[i] == C)
return i;
}
return -1;
}
this is another way of writing:
int f(char C) {
switch (C) {
case ',':
return 0;
case '/':
return 1;
case '\\':
return 2;
case ':'
return 3;
case '.':
return 4;
case ' ':
return 5;
case '\n':
return 6;
case '\t':
return 7;
case '\'':
return 8;
case '-'
return 9;
}
return -1;
}
we should canonicalize the first to the second. pathalogical switches should
be *lower* back to loops for performance.
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