[llvm] [InstCombine][X86] Fold add(vpmadd52(0, a, b), x) -> vpmadd52(x, a, b) (PR #195937)

[Simon Pilgrim via llvm-commits]

================
@@ -0,0 +1,165 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=instcombine -mtriple=x86_64-- -mattr=+avx512ifma -S | FileCheck %s
+
+declare <2 x i64> @llvm.x86.avx512.vpmadd52h.uq.128(<2 x i64>, <2 x i64>, <2 x i64>)
+declare <2 x i64> @llvm.x86.avx512.vpmadd52l.uq.128(<2 x i64>, <2 x i64>, <2 x i64>)
+declare <4 x i64> @llvm.x86.avx512.vpmadd52h.uq.256(<4 x i64>, <4 x i64>, <4 x i64>)
+declare <4 x i64> @llvm.x86.avx512.vpmadd52l.uq.256(<4 x i64>, <4 x i64>, <4 x i64>)
+declare <8 x i64> @llvm.x86.avx512.vpmadd52h.uq.512(<8 x i64>, <8 x i64>, <8 x i64>)
+declare <8 x i64> @llvm.x86.avx512.vpmadd52l.uq.512(<8 x i64>, <8 x i64>, <8 x i64>)
----------------
RKSimon wrote:

these declarations should be unnecessary?

https://github.com/llvm/llvm-project/pull/195937