[AVX-512] `vpternlog` can be used even when a subexpression is consumed

[Validark]

This code: Zig Godbolt LLVM Godbolt

export fn foo(a: @Vector(8, u64), b: @Vector(8, u64), c: @Vector(8, u64)) @Vector(8, u64) {
    const x = a & b;
    const y = a & b & c;
    return x *% y;
}

define dso_local <8 x i64> @foo(<8 x i64> %0, <8 x i64> %1, <8 x i64> %2) local_unnamed_addr {
Entry:
  %3 = and <8 x i64> %1, %0
  %4 = and <8 x i64> %3, %2
  %5 = mul <8 x i64> %4, %3
  ret <8 x i64> %5
}

Compiles to:

        vpandq  zmm0, zmm1, zmm0
        vpandq  zmm1, zmm0, zmm2
        vpmullq zmm0, zmm1, zmm0

Should be:

        vpandq     zmm3, zmm1, zmm0
        vpternlogq zmm2, zmm1, zmm0, 128
        vpmullq    zmm0, zmm2, zmm3

In the current assembly, the second vpandq relies on the input of the first one. vpternlogq, on the other hand, can be computed in parallel to vpandq.

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Niles Salter (Validark)

This code: [Zig Godbolt](https://zig.godbo.lt/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAMzwBtMA7AQwFtMQByARg9KtQYEAysib0QXAMx8BBAKoBnTAAUAHpwAMvAFYTStJg1AAvPMFJL6yAngGVG6AMKpaAVxYM9DgDJ4GmADl3ACNMYhAATmkAB1QFQlsGZzcPPVj4mwFffyCWUPCoi0wrTIYhAiZiAmT3Ty4iksTyyoJswJCwyOkFCqqa1Pqelrbc/K6ASgtUV2Jkdg40Bh6Aah70ZYBSSQARZYABPBZYqogNgCYztfOz8a2AIQ2NAEFHp8xVY4JlqgZv1FQIEwQPsAGqYawkCAADlIy1cADYACyTZbBYF7MEQ4jQ2EI5Gw5DozFEbEwuFI8bjUHgkk48nIzYAdgez2WbOWixWqk2O2WTE2Z3hqPur3ZHIEKwAnjzdvzzkLggKhcgRaz2cRMAQZr9uQAqc4AVmWktVL0Z21er3en2%2Bv2ClUBRJpkLJeJRaOpWLpboJTq9ropVIxztJuIpTJZTzFnK%2B3K2sqVwskkejEq%2B0vjywIYQYgNhwQJsOucsFqMTKout2TovVmu1yz1huNpo25stzx%2BywAbtFs8QGLRUMBHZ7aQH8ai/WOwxPCaOXTOUWgjjY2MtDiwocDXFCg8SF/Sqa2U7Wtf3VgRiK5rBGa2K2e8%2B79O3trrRaF2WAA6VRQ%2BFfpgu1UA0uDOL9exzQdgC/ABHL8QLOa4IGDf1F1hFDp0PdD91DLD10kG551wt1TTFVtti/V8LnfT8fz/ACgIQ8Cnyg2D4NApCmHzQt1xYTcq0jcj2yeAB6MTlgAFSYABrTAFHXBholcL4uxDeSNnhDQmA0jQi004IdNhQx1h0lVNL5Bh1n5Zde0OTAL2IPxgGWa0NQUeIBGWVAqGWBBUAAdyzVBxTyPx7IIBBMBYZYIFceIjGWaJKkYCK5LweTjKzSKlC86IwiYEkFGBDYDQeQVW0cErsAAPxK7Zxi/V4xJE5YACU637DLuwg/soLzVEeIASQAWWG3dln8yKNWWEaxvXeTUr5aJomIVAVrwArwqvCKsyYYJ6D%2BYgsvs4A8FU34ekchLXLkjyGEa55muWbAv2grMcwgVRYUlWFjCLC5qpLIUIEVCqOVuSt7mWcSdO0zS9I0Az4YskzNLMjQ%2BWmxakuIVhNTCeT/Ps60aQU46HKc5YGGClgCr7CaEAK%2BbEqYdzMHWPw%2BQy4hgHcFKFAep5OyfEcMIPH1JyI70KV9KXxyXVAVzslyPnCTZSrqmM4XGsXiPDY87xC2y1y7SpeM3bcoRlZYNFI9kbNXeyDbVe9DpijQvy/caKrwMHnajV37y1hwAH10gJNMLPU3kbLoTA7kIYbDDwaIAAlijy7FdJt2FXIFMq7gFRCDUcVQNFti50MvVwGFEbMIDwHlsC2bBlhuKur1rzaG6blvli4FE9mrrv68blu%2B40Sk7cD9k8B8iBQ/SZYwDATNXK/egGCDWP6GwYhVuxNYvyoFgCC/B27OUK6CFOC5sFV27EmWfB1mpr4d/stB95pWhJWKi587nELnnIBQCi63nNBAi0ldliNWZC5SyYc4i51VhvRgTJ6oCUNjPDcVsKqZj2KzWKZJDAKCPJISqFD1zT3vEJF2GDDYajPL8HsLEhz9QLByWEuCsHPDoS8R64kow2AYNKYIhAAC0tMGApxVitR%2BnkP7EEFk9K%2BhxKh0GlGwQwXwiConsnFdmXkWFiDwOsG67lEgKCMrQCK0xgAIFWIrYm%2B8SAckisgaSlN0rPwEJgV4nYP4JwIEnGRacM5hAgPIuYllGBzG3EiWE6QQ7bniMYTAKCVrFQ1gabYWsdxGW3PUSWrhilzlKVSS614vjHjhGkjJcIuAYNvPQ02R0l6ZmSTQyaccYquRKncdIdUZSZjABwZeHAqQdLOA8XkXAWz0K1vQKgBAQ7IAQEdNeqsBlDNyTQ8O3YzbLJqbyBQ/lCDrJisctZGyjzMmweyMZ1UxkjMkK3IJidk7hNoJnCAiIklxHzv3TJZA%2BTcXBqQB5bIxlMBefGPucDC7TMLsUuU5pIX0LFGM4IcKdgItqci4FZZyIYoDq7MZyBcUWjebAglgKwFlIwaSmeYyIBUr7h8kJXz04/MidnQlxTXJGXBcgSYUKXK0ByvCmlNcNRMHWXtegzL2RCWrHw%2BhZyLmOIgNc9ZxA7knnJRwZ54zpWt2OdbaqxzlVGrZaavFNL/YzzFHPPp2zSq7N2CvUZkyxlUllZgeVjN9r%2BLVWS51yLMzzLDTPEl4rihSoda3A26LDb8MNj0g6EBq6YANeKzN9kF7usGXEYZ0qvXjL9YlelMyo0LPDamJYXw1rW36R60teyY2By1mtMOGo5hYFrk7XkhCFCxUSasc5BBLkQDWnmzFgcMZmpzuKrFvr7XUtbrpVdjyODynZTS6QO7oV7oNNgA9rczg2udWMiqF7gXHolYmzdcIGByoVSG69ZFzS8IEQ22e89okODicO5uvJe1AcHXMKkwQ5XSXrTPA5WtHIOJObsTV07tVzpaf%2Bo1%2B6N0csVtEOOwTQkpx5b86Q1b1IzKJUKsFA0IWPtvWe%2B9nKyPfN%2BVe6jQLBWq2FYx0VX7A63sZI4NjRGSOfLCRRyJxSBUgoE5woTj6E3DpfQGoNiqMnitVYJBdbILWZgwzO7DTrnUnvw6881mAVmJhQwgAgwm8OsYIzSozZ7lgOac8xvdYn71GbE15swjnnP3jU9Z1977g1Kt022LtbJ030KYfWRF1HYSBepYJNszxJn6E4AaXgngOBaFIKgTgAAtMwTiZhzAFJIHgpACCaEmZMaSIAQJfgawRKEUJEQaANBoREBpGQRHhPljgiIistbK5wXgRVdLNZK3luAsAkBKPIJQJRIBjDD2knwOgfYiogxm%2BI5gxA/7cF4GdyokoADywRtA0k4I15cbBBB3YHJd0rWBgiuGAI4MQkqXu8CwNI4A4hlukHwP2mwqkipQ/eOCZS8xGt%2BGzLQGbtA8Cwdu84LAM3LyHBB6QVSxBghxEwNsKKhgIdORa5MKgBhgAKBBHgTA/k7t5WK41/gggRBiHYFIGQghFAqHUFD3Q0gDBGB22YfQOOiqQEmGtUoCOJF3basUQNSgABirMvgSN6MATUDY/whyRBI7HDBXDcikcgJS8ZjAMDJ4VsrZPHJYCVxASYlgaSJHsJZfodRSA%2BDCqMTo9R0gJAEMHtIcQY8MBGB0cIgxtfWCaL0aoLhah6D9xngQzQqjJ7yJHiwWe4%2BDCzyXsYA8pi1aF5MTHHA3fFdK%2BV8ZphnJ7ZirgQgbjzgNfGLwJbWhKSkEikwLA4QfekHa4iKEX54R/kZFwLgBoIiIgiAaREldm9TdICwCQ5dSBt94B3%2BbIBFsM6b5wM402ocX6azf0nBMA%2BIiAA%3D%3D) [LLVM Godbolt](https://llvm.godbolt.org/#z:OYLghAFBqd5QCxAYwPYBMCmBRdBLAF1QCcAaPECAMzwBtMA7AQwFtMQByARg9KtQYEAysib0QXACx8BBAKoBnTAAUAHpwAMvAFYTStJg1C1aANxakl9ZATwDKjdAGFUtAK4sGexwBk8DTAA5DwAjTGIJAA5SAAdUBUI7Bhd3Tz04hNsBPwDgljCIrmirTBskoQImYgIUjy8uS0xrLIYKqoIcoNDwqMtK6tq0hoV%2Bjv8u/J6igEpLVDdiZHYOLBoAgGp0BVQAfVpUUVp1gFIAZidI9dV1vAA2STPsdYABflQIM4urm/vHk4AmACsGlIJ3Ol2udwepyexyBDTBX0hvxhAMB/2m632hx2bgYzDY6B2THQ6GIJwA7AAhY4aACC2EExAAniBaXT1mjTmCACLrQzoREQn7Q2Hw0Fw4HszmSyS8/kMQWfYVQv6S04SoH/aVowHylhuI7K76q1GyzWA0464iYAhCk0osWAwHs44Unmu%2BmrcabbZ7A5ie3I0UvEJVD7gh0hyUgoMitXiuOmp0YrEB2i4/GsTBEklkyk0%2BmMggstn0mVA7lnPkCpOOtEImM62Xyyp0daHI2R4N/Z4mcwAOlUkVuA6YplUgK4/wHMQI4QY%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%2BOMeQFBIIIZIkAgkyAZOxPE9MMJ0VNTCC%2BMtG0AyuHUTMajz5SjBz3SFNzoyM8zIztOLkyS3j8yLM99GMWZLUcRwHY/esEAhQw8mYhAuCECQklcNM0kHQpIDAgO2m6fpWk6Xp0TGaZpBLVwGggixbHa1ZNmkHZWjTOrHD/JrgeWaHtukKtCT2JIQA%3D)

export fn foo(a: @<!-- -->Vector(8, u64), b: @<!-- -->Vector(8, u64), c: @<!-- -->Vector(8, u64)) @<!-- -->Vector(8, u64) {
    const x = a &amp; b;
    const y = a &amp; b &amp; c;
    return x *% y;
}

define dso_local &lt;8 x i64&gt; @<!-- -->foo(&lt;8 x i64&gt; %0, &lt;8 x i64&gt; %1, &lt;8 x i64&gt; %2) local_unnamed_addr {
Entry:
  %3 = and &lt;8 x i64&gt; %1, %0
  %4 = and &lt;8 x i64&gt; %3, %2
  %5 = mul &lt;8 x i64&gt; %4, %3
  ret &lt;8 x i64&gt; %5
}

Compiles to:

        vpandq  zmm0, zmm1, zmm0
        vpandq  zmm1, zmm0, zmm2
        vpmullq zmm0, zmm1, zmm0

Should be:

        vpandq     zmm3, zmm1, zmm0
        vpternlogq zmm2, zmm1, zmm0, 128
        vpmullq    zmm0, zmm2, zmm3

In the current assembly, the second vpandq relies on the input of the first one. vpternlogq, on the other hand, can be computed in parallel to vpandq.