[PATCH v4 1/3] vkd3d-shader/hlsl: Avoid infinite loop in copy propagation.

[Francisco Casas]

From: Francisco Casas

Co-authored-by: Giovanni Mascellani

copy_propagation_transform_object_load() currently retrieves true, which
indicates that there was progress, even if the input dereference remains
the same.

This can happen repeatedly if an uninitialized object is copied onto
itself, as in the tests added in this patch. This results on the
compilation getting stuck on an endless loop.

This patch preempts this by only propagating object loads when the
variable is a real object (i.e., a uniform variable) which cannot have a
replacement, since they cannot be stored to.
---
 libs/vkd3d-shader/hlsl_codegen.c    |  6 +++++
 tests/object-references.shader_test | 37 +++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/libs/vkd3d-shader/hlsl_codegen.c b/libs/vkd3d-shader/hlsl_codegen.c
index 6e4168fc..037c241c 100644
--- a/libs/vkd3d-shader/hlsl_codegen.c
+++ b/libs/vkd3d-shader/hlsl_codegen.c
@@ -773,6 +773,12 @@ static bool copy_propagation_transform_object_load(struct hlsl_ctx *ctx,
     /* Only HLSL_IR_LOAD can produce an object. */
     load = hlsl_ir_load(instr);

+    if (!load->src.var->is_uniform)
+    {
+        TRACE("Ignoring load from non-uniform object variable %s\n", load->src.var->name);
+        return false;
+    }
+
     hlsl_cleanup_deref(deref);
     hlsl_copy_deref(ctx, deref, &load->src);

diff --git a/tests/object-references.shader_test b/tests/object-references.shader_test
index 12f745e6..78fabd79 100644
--- a/tests/object-references.shader_test
+++ b/tests/object-references.shader_test
@@ -1,3 +1,15 @@
+[pixel shader fail todo]
+sampler sam;
+
+float4 main() : sv_target
+{
+    Texture2D tex;
+
+    tex = tex; // Uninitialized assignment to self.
+    return tex.Sample(sam, float2(0, 0));
+}
+
+
 [require]
 shader model >= 4.0

@@ -155,3 +167,28 @@ float4 main() : sv_target
 uniform 0 float 10.0
 todo draw quad
 todo probe (0, 0) rgba (11.0, 12.0, 13.0, 11.0)
+
+
+[require]
+shader model >= 5.0
+
+
+[texture 0]
+size (1, 1)
+1.0 2.0 3.0 4.0
+
+[pixel shader todo]
+struct apple {
+    Texture2D tex;
+    float4 fo : COLOR;
+};
+
+float4 main(struct apple input) : sv_target
+{
+    input.tex = input.tex; // Assignment to self.
+    return input.tex.Load(int3(0, 0, 0));
+}
+
+[test]
+todo draw quad
+todo probe (0, 0) rgba (1.0, 2.0, 3.0, 4.0)