https://bugs.llvm.org/show_bug.cgi?id=35091
Bug ID: 35091
Summary: AArch64 backend does not handle contract math.
Product: libraries
Version: 5.0
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: AArch64
Assignee: unassignedb...@nondot.org
Reporter: yyc1...@gmail.com
CC: llvm-bugs@lists.llvm.org
Test case:
```
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
define double @f1(double, double, double) {
%4 = call double @llvm.fmuladd.f64(double %0, double %1, double %2)
ret double %4
}
define double @f2(double, double, double) {
%4 = fmul contract double %0, %1
%5 = fadd contract double %4, %2
ret double %5
}
declare double @llvm.fmuladd.f64(double %a, double %b, double %c)
```
According to LangRef, the two function should be the same and should both use
fma or mul and add depending on what the backend think is faster. However,
running with `llc -O3` only the first one generates an fma instruction and the
second one uses a mul and an add.
ARM backend might have the same issue.
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