ac/llvm: implement nir_op_unpack_32_4x8

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19399>

src/amd/llvm/ac_llvm_build.c

@@ -85,6 +85,7 @@ void ac_llvm_context_init(struct ac_llvm_context *ctx, struct ac_llvm_compiler *
    ctx->f16 = LLVMHalfTypeInContext(ctx->context);
    ctx->f32 = LLVMFloatTypeInContext(ctx->context);
    ctx->f64 = LLVMDoubleTypeInContext(ctx->context);
+   ctx->v4i8 = LLVMVectorType(ctx->i8, 4);
    ctx->v2i16 = LLVMVectorType(ctx->i16, 2);
    ctx->v4i16 = LLVMVectorType(ctx->i16, 4);
    ctx->v2f16 = LLVMVectorType(ctx->f16, 2);

src/amd/llvm/ac_llvm_build.h

@@ -96,6 +96,7 @@ struct ac_llvm_context {
    LLVMTypeRef f16;
    LLVMTypeRef f32;
    LLVMTypeRef f64;
+   LLVMTypeRef v4i8;
    LLVMTypeRef v2i16;
    LLVMTypeRef v4i16;
    LLVMTypeRef v2f16;

src/amd/llvm/ac_nir_to_llvm.c

@@ -543,6 +543,7 @@ static bool visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
    case nir_op_vec5:
    case nir_op_vec8:
    case nir_op_vec16:
+   case nir_op_unpack_32_4x8:
    case nir_op_unpack_32_2x16:
    case nir_op_unpack_64_2x32:
    case nir_op_unpack_64_4x16:
@@ -1223,6 +1224,9 @@ static bool visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
       break;
    }
 
+   case nir_op_unpack_32_4x8:
+      result = LLVMBuildBitCast(ctx->ac.builder, src[0], ctx->ac.v4i8, "");
+      break;
    case nir_op_unpack_32_2x16: {
       result = LLVMBuildBitCast(ctx->ac.builder, src[0],
             ctx->ac.v2i16, "");