ac: add ac_build_bifield_reverse() helper

Are we missing 64-bit support?

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/common/ac_llvm_build.c

@@ -2135,6 +2135,28 @@ LLVMValueRef ac_build_bit_count(struct ac_llvm_context *ctx, LLVMValueRef src0)
 	return result;
 }
 
+LLVMValueRef ac_build_bitfield_reverse(struct ac_llvm_context *ctx,
+				       LLVMValueRef src0)
+{
+	LLVMValueRef result;
+	unsigned bitsize;
+
+	bitsize = ac_get_elem_bits(ctx, LLVMTypeOf(src0));
+
+	switch (bitsize) {
+	case 32:
+		result = ac_build_intrinsic(ctx, "llvm.bitreverse.i32", ctx->i32,
+					    (LLVMValueRef []) { src0 }, 1,
+					    AC_FUNC_ATTR_READNONE);
+		break;
+	default:
+		unreachable(!"invalid bitsize");
+		break;
+	}
+
+	return result;
+}
+
 #define AC_EXP_TARGET		0
 #define AC_EXP_ENABLED_CHANNELS 1
 #define AC_EXP_OUT0		2

src/amd/common/ac_llvm_build.h

@@ -426,6 +426,9 @@ LLVMValueRef ac_build_fsign(struct ac_llvm_context *ctx, LLVMValueRef src0,
 
 LLVMValueRef ac_build_bit_count(struct ac_llvm_context *ctx, LLVMValueRef src0);
 
+LLVMValueRef ac_build_bitfield_reverse(struct ac_llvm_context *ctx,
+				       LLVMValueRef src0);
+
 void ac_optimize_vs_outputs(struct ac_llvm_context *ac,
 			    LLVMValueRef main_fn,
 			    uint8_t *vs_output_param_offset,

src/amd/common/ac_nir_to_llvm.c

@@ -836,7 +836,7 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 		result = emit_bitfield_insert(&ctx->ac, src[0], src[1], src[2], src[3]);
 		break;
 	case nir_op_bitfield_reverse:
-		result = ac_build_intrinsic(&ctx->ac, "llvm.bitreverse.i32", ctx->ac.i32, src, 1, AC_FUNC_ATTR_READNONE);
+		result = ac_build_bitfield_reverse(&ctx->ac, src[0]);
 		break;
 	case nir_op_bit_count:
 		result = ac_build_bit_count(&ctx->ac, src[0]);