[llvm] [AArch64] Make use of byte FPR stores for bytes extracted from vectors (PR #134117)

[Paul Walker via llvm-commits]

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@@ -4589,6 +4589,18 @@ def : Pat<(truncstorei16 GPR64:$Rt, (am_unscaled16 GPR64sp:$Rn, simm9:$offset)),
 def : Pat<(truncstorei8 GPR64:$Rt, (am_unscaled8 GPR64sp:$Rn, simm9:$offset)),
   (STURBBi (EXTRACT_SUBREG GPR64:$Rt, sub_32), GPR64sp:$Rn, simm9:$offset)>;
 
+// v1i64 -> bsub truncating stores
+// Supporting pattern lower f32/64 -> v8i8
+def : Pat<(v8i8 (vector_insert (v8i8 (undef)), (i32 FPR32:$src), 0)),
+          (INSERT_SUBREG (v8i8 (IMPLICIT_DEF)), FPR32:$src, ssub)>;
+def : Pat<(v8i8 (vector_insert (v8i8 (undef)), (i64 FPR64:$src), 0)),
+          (v8i8 (EXTRACT_SUBREG (INSERT_SUBREG (v16i8 (IMPLICIT_DEF)), FPR64:$src, dsub), dsub))>;
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paulwalker-arm wrote:

My hope is that with the combine rewrite these can be removed.

https://github.com/llvm/llvm-project/pull/134117