| Issue |
137575
|
| Summary |
[AVX-512] Propagating lowest bit to all bits in u64 lane should use `sra(sll(x, 63), 63)` instead of `neg(and(x, 1))`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Validark
|
[Zig Godbolt](https://zig.godbo.lt/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:13,fontUsePx:'0',j:1,lang:zig,selection:(endColumn:1,endLineNumber:13,positionColumn:1,positionLineNumber:13,selectionStartColumn:1,selectionStartLineNumber:13,startColumn:1,startLineNumber:13),source:'export+fn+foo(vec:+@Vector(8,+u64))+@Vector(8,+u64)+%7B%0A++++return+-%25((vec+%3C%3C+@splat(63))+%3E%3E+@splat(63))%3B%0A%7D%0A%0Aexport+fn+bar(vec:+@Vector(8,+u64))+@Vector(8,+u64)+%7B%0A++++return+asm+(%0A++++++++%5C%5C+vpsllq+$63,+%25%5Bvec%5D,+%25%5Bresult%5D%0A++++++++%5C%5C+vpsraq+$63,+%25%5Bresult%5D,+%25%5Bresult%5D%0A++++++++:+%5Bresult%5D+%22%3Dx%22+(-%3E+@Vector(8,+u64)),%0A++++++++:+%5Bvec%5D+%22x%22+(vec),%0A++++)%3B%0A%7D%0A'),l:'5',n:'0',o:'Zig+source+%231',t:'0')),k:51.313288405045796,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:ztrunk,filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1',verboseDemangling:'0'),flagsViewOpen:'1',fontScale:13,fontUsePx:'0',j:3,lang:zig,libs:!(),options:'-O+ReleaseFast+-target+x86_64-linux+-mcpu%3Dznver5',overrides:!(),selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:'5',n:'0',o:'+zig+trunk+(Editor+%231)',t:'0')),header:(),k:48.68671159495422,l:'4',m:100,n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4) [LLVM Godbolt](https://llvm.godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:llvm,selection:(endColumn:1,endLineNumber:13,positionColumn:1,positionLineNumber:13,selectionStartColumn:1,selectionStartLineNumber:13,startColumn:1,startLineNumber:13),source:'define+dso_local+range(i64+-1,+1)+%3C8+x+i64%3E+@foo(%3C8+x+i64%3E+%250)+local_unnamed_addr+%7B%0AEntry:%0A++%251+%3D+and+%3C8+x+i64%3E+%250,+splat+(i64+1)%0A++%252+%3D+sub+nsw+%3C8+x+i64%3E+zeroinitializer,+%251%0A++ret+%3C8+x+i64%3E+%252%0A%7D%0A%0Adefine+dso_local+%3C8+x+i64%3E+@bar(%3C8+x+i64%3E+%250)+local_unnamed_addr+%7B%0AEntry:%0A++%251+%3D+tail+call+%3C8+x+i64%3E+asm+%22+vpsllq+$$63,+$%7B1%7D,+$%7B0%7D%5C0A+vpsraq+$$63,+$%7B0%7D,+$%7B0%7D%22,+%22%3Dx,x,~%7Bdirflag%7D,~%7Bfpsr%7D,~%7Bflags%7D%22(%3C8+x+i64%3E+%250)+%232%0A++ret+%3C8+x+i64%3E+%251%0A%7D%0A'),l:'5',n:'0',o:'LLVM+IR+source+%231',t:'0')),k:49.178082191780824,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:irclangtrunk,filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1',verboseDemangling:'0'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:1,lang:llvm,libs:!(),options:'-O3+-march%3Dznver5',overrides:!(),selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:'5',n:'0',o:'+clang+(trunk)+(Editor+%231)',t:'0')),k:50.82191780821918,l:'4',m:100,n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4)
```zig
export fn foo(vec: @Vector(8, u64)) @Vector(8, u64) {
return -%((vec << @splat(63)) >> @splat(63));
}
```
Gives:
```asm
.LCPI0_0:
.quad 1
foo:
vpandq zmm0, zmm0, qword ptr [rip + .LCPI0_0]{1to8}
vpxor xmm1, xmm1, xmm1
vpsubq zmm0, zmm1, zmm0
ret
```
Should be:
```asm
foo:
vpsllq zmm0, zmm0, 63
vpsraq zmm0, zmm0, 63
ret
```
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