[llvm] [RISCV] Bitcast fixed length bf16/f16 build_vector to i16 with Zvfbfmin/Zvfhmin+Zfbfmin/Zfhmin. (PR #106637)

[Philip Reames via llvm-commits]

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@@ -0,0 +1,175 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -target-abi=ilp32d -mattr=+v,+zvfbfmin,+f,+d -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV32,RV32ZVFBFMIN,RV32-NO-ZFBFMIN
+; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zvfbfmin,+f,+d -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64,RV64ZVFBFMIN,RV64-NO-ZFBFMIN
+; RUN: llc -mtriple=riscv32 -target-abi=ilp32d -mattr=+v,+zfbfmin,+zvfbfmin,+f,+d -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV32,RV32ZVFBFMIN,RV32-ZFBFMIN
+; RUN: llc -mtriple=riscv64 -target-abi=lp64d -mattr=+v,+zfbfmin,+zvfbfmin,+f,+d -verify-machineinstrs < %s | FileCheck %s --check-prefixes=CHECK,RV64,RV64ZVFBFMIN,RV64-ZFBFMIN
+
+define <4 x bfloat> @splat_idx_v4bf16(<4 x bfloat> %v, i64 %idx) {
+; RV32-NO-ZFBFMIN-LABEL: splat_idx_v4bf16:
+; RV32-NO-ZFBFMIN:       # %bb.0:
+; RV32-NO-ZFBFMIN-NEXT:    vsetivli zero, 4, e16, mf2, ta, ma
+; RV32-NO-ZFBFMIN-NEXT:    vrgather.vx v9, v8, a0
+; RV32-NO-ZFBFMIN-NEXT:    vmv1r.v v8, v9
+; RV32-NO-ZFBFMIN-NEXT:    ret
+;
+; RV64-NO-ZFBFMIN-LABEL: splat_idx_v4bf16:
+; RV64-NO-ZFBFMIN:       # %bb.0:
+; RV64-NO-ZFBFMIN-NEXT:    vsetivli zero, 4, e16, mf2, ta, ma
+; RV64-NO-ZFBFMIN-NEXT:    vrgather.vx v9, v8, a0
+; RV64-NO-ZFBFMIN-NEXT:    vmv1r.v v8, v9
+; RV64-NO-ZFBFMIN-NEXT:    ret
+;
+; RV32-ZFBFMIN-LABEL: splat_idx_v4bf16:
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preames wrote:

The fact that the version *with* the extension generates worse code than the one *without* seems not ideal.

https://github.com/llvm/llvm-project/pull/106637