[PATCH 0/1] MR338: vkd3d-shader/hlsl: Correctly fold casts from float.

[PATCH 1/1] vkd3d-shader/hlsl: Correctly fold casts from float.

[Giovanni Mascellani]

From: Giovanni Mascellani

I.e., without invoking undefined behavior in the compiler. The rules
are desumed from the the MSDN documentation for ftoi and ftou.
---
 libs/vkd3d-shader/hlsl_constant_ops.c | 29 +++++++++++++++++++++++++--
 tests/hlsl/cast-to-uint.shader_test   |  2 +-
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/libs/vkd3d-shader/hlsl_constant_ops.c b/libs/vkd3d-shader/hlsl_constant_ops.c
index 41a72ab6c..0057b525b 100644
--- a/libs/vkd3d-shader/hlsl_constant_ops.c
+++ b/libs/vkd3d-shader/hlsl_constant_ops.c
@@ -63,6 +63,31 @@ static bool fold_abs(struct hlsl_ctx *ctx, struct hlsl_constant_value *dst,
     return true;
 }

+static uint32_t fold_float_to_unsigned(float x)
+{
+    if (isnan(x) || x <= 0)
+        return 0;
+
+    if (x >= 4294967296.0f)
+        return UINT32_MAX;
+
+    return (uint32_t)x;
+}
+
+static int32_t fold_float_to_int(float x)
+{
+    if (isnan(x))
+        return 0;
+
+    if (x <= -2147483648.0f)
+        return INT32_MIN;
+
+    if (x >= 2147483648.0f)
+        return INT32_MAX;
+
+    return (int32_t)x;
+}
+
 static bool fold_cast(struct hlsl_ctx *ctx, struct hlsl_constant_value *dst,
         const struct hlsl_type *dst_type, const struct hlsl_ir_constant *src)
 {
@@ -86,8 +111,8 @@ static bool fold_cast(struct hlsl_ctx *ctx, struct hlsl_constant_value *dst,
         {
             case HLSL_TYPE_FLOAT:
             case HLSL_TYPE_HALF:
-                u = src->value.u[k].f;
-                i = src->value.u[k].f;
+                u = fold_float_to_unsigned(src->value.u[k].f);
+                i = fold_float_to_int(src->value.u[k].f);
                 f = src->value.u[k].f;
                 d = src->value.u[k].f;
                 break;
diff --git a/tests/hlsl/cast-to-uint.shader_test b/tests/hlsl/cast-to-uint.shader_test
index 4ffc041ad..93862a36f 100644
--- a/tests/hlsl/cast-to-uint.shader_test
+++ b/tests/hlsl/cast-to-uint.shader_test
@@ -41,4 +41,4 @@ float4 main() : sv_target

[test]
 draw quad
-todo probe all rgba (0.5, 0.5, 0.5, 0.5)
+probe all rgba (0.5, 0.5, 0.5, 0.5)

[Zebediah Figura (＠zfigura)]

Oof, I wrote these too, but you beat me to it :x

I'd remove the "fold" from the function names, since they're not folding anything by themselves. (Also, "float_to_uint" instead of "float_to_unsigned"?)

This doesn't deal with double comparisons. I think you can reuse the same functions by changing their arguments to doubles.

The explicit casts seem superfluous.