Allow loop counters to be used as constexpr arguments. (#3139)

* Allow loop counters to be used as constexpr arguments.

* Fix.

* Fix.

* Fix.

* Fix.

---------

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

6 files changed, 35 insertions, 0 deletions

diff --git a/tests/diagnostics/autodiff-data-flow-2.slang b/tests/diagnostics/autodiff-data-flow-2.slang
index 3148c6a41..42aee0d01 100644
--- a/tests/diagnostics/autodiff-data-flow-2.slang
+++ b/tests/diagnostics/autodiff-data-flow-2.slang
@@ -28,6 +28,7 @@ float h(float x)
     // error: dynamic loop without [MaxIters] or [ForceUnroll]
     for (int i = 0; i < (int)x; i++)
     {
+        no_diff debugBreak();
     }
 
     return val;
diff --git a/tests/diagnostics/autodiff-data-flow.slang b/tests/diagnostics/autodiff-data-flow.slang
index e8d9502e4..bbade0e0a 100644
--- a/tests/diagnostics/autodiff-data-flow.slang
+++ b/tests/diagnostics/autodiff-data-flow.slang
@@ -28,6 +28,7 @@ void g(float x)
     for (int i = 0; i < 5; i++) // Not ok, we can't infer the loop iterations because the body modifies induction var.
     {
         i = (int)x;
+        no_diff debugBreak();
     }
     return;
 }
diff --git a/tests/diagnostics/constexpr-error.slang.expected b/tests/diagnostics/constexpr-error.slang.expected
index f6c27b006..6f124fe34 100644
--- a/tests/diagnostics/constexpr-error.slang.expected
+++ b/tests/diagnostics/constexpr-error.slang.expected
@@ -6,9 +6,15 @@ tests/diagnostics/constexpr-error.slang(27): error 40006: expected a compile-tim
 tests/diagnostics/constexpr-error.slang(35): error 40006: expected a compile-time constant
     result += t.Sample(s, uv, int2(ii));
                                   ^
+tests/diagnostics/constexpr-error.slang(39): error 40006: expected a compile-time constant
+    for(uint jj = 0; jj < uv.y; jj++)
+                     ^~
 tests/diagnostics/constexpr-error.slang(41): error 40006: expected a compile-time constant
         result += t.Sample(s, uv, int2(jj));
                                       ^
+tests/diagnostics/constexpr-error.slang(39): error 40006: expected a compile-time constant
+    for(uint jj = 0; jj < uv.y; jj++)
+                                  ^~
 }
 standard output = {
 }
diff --git a/tests/expected-failure.txt b/tests/expected-failure.txt
index f40435ec1..98cf36724 100644
--- a/tests/expected-failure.txt
+++ b/tests/expected-failure.txt
@@ -152,6 +152,7 @@ tests/hlsl-intrinsic/wave-mask/wave-vector.slang.3 (vk)
 tests/hlsl-intrinsic/wave-mask/wave.slang.3 (vk)
 tests/ir/loop-unroll-0.slang.1 (vk)
 tests/ir/string-literal-hash.slang.1 (vk)
+tests/language-feature/constants/constexpr-loop.slang.1 (vk)
 tests/language-feature/general-inline.slang.1 (vk)
 tests/language-feature/simple-inline.slang.1 (vk)
 tests/language-feature/initializer-lists/default-init-16bit-types.slang (vk)
diff --git a/tests/language-feature/constants/constexpr-loop.slang b/tests/language-feature/constants/constexpr-loop.slang
new file mode 100644
index 000000000..31b4294a5
--- /dev/null
+++ b/tests/language-feature/constants/constexpr-loop.slang
@@ -0,0 +1,24 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+
+//TEST_INPUT: set g_texture = Texture2D(size=8, content = one)
+//TEST_INPUT: set g_sampler = Sampler
+//TEST_INPUT:ubuffer(data=[0], stride=4):out,name=outputBuffer
+
+Texture2D g_texture;
+SamplerState g_sampler;
+RWStructuredBuffer<float> outputBuffer;
+
+float4 sample(float2 uv, constexpr int2 ofs )
+{
+    return g_texture.SampleLevel(g_sampler, uv, 0.0, ofs); 
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(int3 dispatchThreadID: SV_DispatchThreadID)
+{
+    float4 result = 0;
+    for (int i = 0; i < 3; i++)
+        result += sample(float2(1.0), int2(i, i));
+    outputBuffer[dispatchThreadID.x] = result.x;
+}
diff --git a/tests/language-feature/constants/constexpr-loop.slang.expected.txt b/tests/language-feature/constants/constexpr-loop.slang.expected.txt
new file mode 100644
index 000000000..a6122d7ce
--- /dev/null
+++ b/tests/language-feature/constants/constexpr-loop.slang.expected.txt
@@ -0,0 +1,2 @@
+type: float
+3.000000