Detect and deduplicate read-only resource access. (#2680)

* Detect and deduplicate read-only resource access.

* Fix tests.

* Fix tests.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

2 files changed, 48 insertions, 0 deletions

diff --git a/tests/autodiff/global-param-hoisting.slang b/tests/autodiff/global-param-hoisting.slang
new file mode 100644
index 000000000..72a9494fe
--- /dev/null
+++ b/tests/autodiff/global-param-hoisting.slang
@@ -0,0 +1,42 @@
+// Test that the compiler can hoist the texture sample out of the loop.
+// We currently have no way to verify the hoist actually take place, but this test
+// allows us to manually inspect the generated code to see that happen.
+// TODO: use a pattern checker on the resulting code to make sure there is only
+// one call to `SampleLevel`.
+
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX:-cpu -compute -output-using-type -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+struct Params : IDifferentiable
+{
+    Texture2D tex;
+    SamplerState sampler;
+}
+
+//TEST_INPUT:set gParams = new Params{Texture2D(size=4, content=one), Sampler}
+ParameterBlock<Params> gParams;
+
+[BackwardDifferentiable]
+float f(float x)
+{
+    float sum = 0.0;
+    for (int i = 0; i < 3; i++)
+    {
+        float t = (no_diff gParams.tex.SampleLevel(gParams.sampler, float2(0.0), 0)).x;
+        sum += t * x * x;
+    }
+    return sum;
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    var dpa = diffPair(3.0);
+
+    __bwd_diff(f)(dpa, 1.0);
+    outputBuffer[0] = dpa.d.x; // Expect: 18
+}
diff --git a/tests/autodiff/global-param-hoisting.slang.expected.txt b/tests/autodiff/global-param-hoisting.slang.expected.txt
new file mode 100644
index 000000000..05d0a2ffd
--- /dev/null
+++ b/tests/autodiff/global-param-hoisting.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+18.000000
+0.000000
+0.000000
+0.000000
+0.000000