https://bugs.llvm.org/show_bug.cgi?id=45683
Bug ID: 45683
Summary: Bad optimization of simple switch
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: gabrav...@gmail.com
CC: llvm-bugs@lists.llvm.org
int f(unsigned x)
{
switch (x)
{
case 0:
return 1;
case 1:
return 2;
}
}
This gets optimized to some rather weird code (uses `sbb` on x86) when it could
just be optimized to `return x + 1`. See here for an example of the bad
generation : https://godbolt.org/z/2fQmpH
Maybe we could change the translation of `select` (as it is used in the IR this
translates to) in order to detect cases such as this and optimize them properly
?
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