https://bugs.llvm.org/show_bug.cgi?id=43497
Bug ID: 43497
Summary: Missed optimization: Conditional multiply by -1.0 or
1.0 not simplified to negation
Product: libraries
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Conditionally multiplying a f64 by -1.0 or 1.0 does not get optimized into a
conditional negation.
Code to reproduce:
pub fn a(num: f64, is_neg: bool) -> f64 {
num * if is_neg {
-1.0
} else {
1.0
}
}
pub fn b(num: f64, is_neg: bool) -> f64 {
if is_neg {
-num
} else {
num
}
}
https://rust.godbolt.org/z/wp28oz
Function a does not get optimized as the same as function b. The equivalent C++
code is properly optimized in GCC.
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