From d6067db06267e37dec65202667741bc1b63fe980 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Fri, 29 Oct 2021 17:48:34 -0700
Subject: stage2: implement `@popCount` for non-vectors

---
 src/codegen/llvm.zig | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'src/codegen/llvm.zig')

diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 572e23ff28..683ee9b95b 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -1777,6 +1777,7 @@ pub const FuncGen = struct {
                 .get_union_tag  => try self.airGetUnionTag(inst),
                 .clz            => try self.airClzCtz(inst, "ctlz"),
                 .ctz            => try self.airClzCtz(inst, "cttz"),
+                .popcount       => try self.airPopCount(inst, "ctpop"),
 
                 .atomic_store_unordered => try self.airAtomicStore(inst, .Unordered),
                 .atomic_store_monotonic => try self.airAtomicStore(inst, .Monotonic),
@@ -3679,6 +3680,40 @@ pub const FuncGen = struct {
         }
     }
 
+    fn airPopCount(self: *FuncGen, inst: Air.Inst.Index, prefix: [*:0]const u8) !?*const llvm.Value {
+        if (self.liveness.isUnused(inst)) return null;
+
+        const ty_op = self.air.instructions.items(.data)[inst].ty_op;
+        const operand_ty = self.air.typeOf(ty_op.operand);
+        const operand = try self.resolveInst(ty_op.operand);
+        const target = self.dg.module.getTarget();
+        const bits = operand_ty.intInfo(target).bits;
+
+        var fn_name_buf: [100]u8 = undefined;
+        const llvm_fn_name = std.fmt.bufPrintZ(&fn_name_buf, "llvm.{s}.i{d}", .{
+            prefix, bits,
+        }) catch unreachable;
+        const fn_val = self.dg.object.llvm_module.getNamedFunction(llvm_fn_name) orelse blk: {
+            const operand_llvm_ty = try self.dg.llvmType(operand_ty);
+            const param_types = [_]*const llvm.Type{operand_llvm_ty};
+            const fn_type = llvm.functionType(operand_llvm_ty, &param_types, param_types.len, .False);
+            break :blk self.dg.object.llvm_module.addFunction(llvm_fn_name, fn_type);
+        };
+
+        const params = [_]*const llvm.Value{operand};
+        const wrong_size_result = self.builder.buildCall(fn_val, &params, params.len, .C, .Auto, "");
+        const result_ty = self.air.typeOfIndex(inst);
+        const result_llvm_ty = try self.dg.llvmType(result_ty);
+        const result_bits = result_ty.intInfo(target).bits;
+        if (bits > result_bits) {
+            return self.builder.buildTrunc(wrong_size_result, result_llvm_ty, "");
+        } else if (bits < result_bits) {
+            return self.builder.buildZExt(wrong_size_result, result_llvm_ty, "");
+        } else {
+            return wrong_size_result;
+        }
+    }
+
     fn callFloor(self: *FuncGen, arg: *const llvm.Value, ty: Type) !*const llvm.Value {
         return self.callFloatUnary(arg, ty, "floor");
     }
-- 
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