| Issue |
131587
|
| Summary |
[x86-64 BMI1] Missed `blsi`emit when `& x` can be unnecessarily factored out of `(x & -x)`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Validark
|
This code: ([Zig Godbolt](https://zig.godbo.lt/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:zig,selection:(endColumn:1,endLineNumber:11,positionColumn:1,positionLineNumber:11,selectionStartColumn:1,selectionStartLineNumber:11,startColumn:1,startLineNumber:11),source:'export+fn+z(b:+bool,+x:+u64)+u64+%7B%0A++++const+y+%3D+x+%26+-%25x%3B+//+blsi%0A++++return+if+(b)+y+else+x%3B%0A%7D%0A%0Aexport+fn+z2(b:+bool,+x:+u64)+u64+%7B%0A++++const+y+%3D+blsi(x)%3B%0A++++return+if+(b)+y+else+x%3B%0A%7D%0A%0Afn+blsi(a:+u64)+u64+%7B%0A++++return+asm+(%22blsi+%25%5Ba%5D,+%25%5Bret%5D%22%0A++++++++:+%5Bret%5D+%22%3Dr%22+(-%3E+u64),%0A++++++++:+%5Ba%5D+%22r%22+(a),%0A++++)%3B%0A%7D'),l:'5',n:'0',o:'Zig+source+%231',t:'0')),k:50,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:14,fontUsePx:'0',j:2,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:50,l:'4',m:100,n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4)) ([LLVM Godbolt](https://llvm.godbo.lt/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:llvm,selection:(endColumn:1,endLineNumber:21,positionColumn:1,positionLineNumber:21,selectionStartColumn:1,selectionStartLineNumber:21,startColumn:1,startLineNumber:21),source:'define+dso_local+i64+@z(i1+zeroext+%250,+i64+%251)+local_unnamed_addr+%7B%0AEntry:%0A++%252+%3D+sub+i64+0,+%251%0A++%253+%3D+select+i1+%250,+i64+%252,+i64+-1%0A++%25.+%3D+and+i64+%253,+%251%0A++ret+i64+%25.%0A%7D%0A%0Adefine+dso_local+i64+@z2(i1+zeroext+%250,+i64+%251)+local_unnamed_addr+%7B%0AEntry:%0A++%252+%3D+tail+call+i64+asm+%22blsi+$%7B1%7D,+$%7B0%7D%22,+%22%3Dr,r,~%7Bdirflag%7D,~%7Bfpsr%7D,~%7Bflags%7D%22(i64+%251)+%232%0A++%25.+%3D+select+i1+%250,+i64+%252,+i64+%251%0A++ret+i64+%25.%0A%7D%0A%0Adefine+dso_local+i64+@blsi(i64+%250)+local_unnamed_addr+%7B%0AEntry:%0A++%251+%3D+tail+call+i64+asm+%22blsi+$%7B1%7D,+$%7B0%7D%22,+%22%3Dr,r,~%7Bdirflag%7D,~%7Bfpsr%7D,~%7Bflags%7D%22(i64+%250)+%232%0A++ret+i64+%251%0A%7D%0A'),l:'5',n:'0',o:'LLVM+IR+source+%231',t:'0')),k:48.76712328767123,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:51.23287671232877,l:'4',m:100,n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4))
```zig
export fn z(b: bool, x: u64) u64 {
const y = x & -%x; // blsi
return if (b) y else x;
}
```
Gives:
```asm
mov rcx, rsi
neg rcx
test edi, edi
mov rax, -1
cmovne rax, rcx
and rax, rsi
```
It should be:
```asm
blsi rax, rsi
test edi, edi
cmove rax, rsi
```
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