https://bugs.llvm.org/show_bug.cgi?id=41456
Bug ID: 41456
Summary: Suboptimal codegen for {x, y} ↦ {x+x, x+y}
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
https://godbolt.org/z/2GE_vO
-----
The code snippet
```
#include <xmmintrin.h>
__m128i example(const __m128i vec) {
return (__m128i){2 * vec[0], vec[0] + vec[1]};
}
```
is compiled to code that unpacks and repacks the values to the general purpose
registers. This uses 7 instructions. However, the same could easily be achieved
using
```
example:
vpbroadcastq xmm1, xmm0
vpaddq xmm0, xmm0, xmm1
ret
```.
Other instructions, instead of vpbroadcastq can also be used; like vmovddup,
vpermilpd, etc.
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