From e569245e1f4bc79fea1334db8649cb6f087fb3c5 Mon Sep 17 00:00:00 2001
From: Henri Verbeet <hverbeet@locutus.nl>
Date: Wed, 3 Sep 2025 20:51:21 +0200
Subject: [PATCH] vkd3d-shader/hlsl: Implement constant folding of 'round'
 expressions.

---
 libs/vkd3d-shader/hlsl_constant_ops.c | 33 +++++++++++++++++++++++++++
 tests/hlsl/round.shader_test          |  2 +-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/libs/vkd3d-shader/hlsl_constant_ops.c b/libs/vkd3d-shader/hlsl_constant_ops.c
index 492969ec6..252ed51a4 100644
--- a/libs/vkd3d-shader/hlsl_constant_ops.c
+++ b/libs/vkd3d-shader/hlsl_constant_ops.c
@@ -521,6 +521,35 @@ static bool fold_reinterpret(struct hlsl_ctx *ctx, struct hlsl_constant_value *d
     return true;
 }
 
+static bool fold_round(struct hlsl_ctx *ctx, struct hlsl_constant_value *dst,
+        const struct hlsl_type *dst_type, const struct hlsl_ir_constant *src)
+{
+    enum hlsl_base_type type = dst_type->e.numeric.type;
+    unsigned int k;
+
+    VKD3D_ASSERT(type == src->node.data_type->e.numeric.type);
+
+    for (k = 0; k < dst_type->e.numeric.dimx; ++k)
+    {
+        switch (type)
+        {
+            case HLSL_TYPE_FLOAT:
+            case HLSL_TYPE_HALF:
+                /* Somewhat unfortunately, constant folded round() rounds
+                 * halfway cases towards positive infinity, as opposed to
+                 * nearest even like vsir/TPF round_ne. */
+                dst->u[k].f = floorf(src->value.u[k].f + 0.5f);
+                break;
+
+            default:
+                FIXME("Fold 'round' for type %s.\n", debug_hlsl_type(ctx, dst_type));
+                return false;
+        }
+    }
+
+    return true;
+}
+
 static bool fold_rsq(struct hlsl_ctx *ctx, struct hlsl_constant_value *dst, const struct hlsl_type *dst_type,
         const struct hlsl_ir_constant *src, const struct vkd3d_shader_location *loc)
 {
@@ -1410,6 +1439,10 @@ bool hlsl_fold_constant_exprs(struct hlsl_ctx *ctx, struct hlsl_ir_node *instr,
             success = fold_reinterpret(ctx, &res, instr->data_type, arg1);
             break;
 
+        case HLSL_OP1_ROUND:
+            success = fold_round(ctx, &res, instr->data_type, arg1);
+            break;
+
         case HLSL_OP1_RSQ:
             success = fold_rsq(ctx, &res, instr->data_type, arg1, &instr->loc);
             break;
diff --git a/tests/hlsl/round.shader_test b/tests/hlsl/round.shader_test
index 9fb087974..785354da3 100644
--- a/tests/hlsl/round.shader_test
+++ b/tests/hlsl/round.shader_test
@@ -53,5 +53,5 @@ float4 main() : sv_target
 
 [test]
 draw quad
-if(sm<6)  todo(sm>=4) probe (0, 0) f32(-1.0,  0.0, 1.0, 2.0)
+if(sm<6)  probe (0, 0) f32(-1.0,  0.0, 1.0, 2.0)
 if(sm>=6) probe (0, 0) f32(-2.0, -0.0, 0.0, 2.0)