Extend `countbits` intrinsic for vector types (#4499)

* Extend `countbits` intrinsic for vector types

This commit implements the overloading function for `countbits` function.
Because HLSL has following overloadings,
```
uint count_bits(uint value);
uint2 count_bits(uint2 value);
uint3 count_bits(uint3 value);
uint4 count_bits(uint4 value);
```
https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/countbits

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/hlsl-intrinsic/countbits.slang b/tests/hlsl-intrinsic/countbits.slang
new file mode 100644
index 000000000..da6828e87
--- /dev/null
+++ b/tests/hlsl-intrinsic/countbits.slang
@@ -0,0 +1,27 @@
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -compute -cpu
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -compute -dx11
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -compute -dx12
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -vk -compute
+//DISABLE_TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -cuda -compute
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHK):-slang -mtl -compute
+
+//CHK:1
+
+//TEST_INPUT:ubuffer(data=[0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    uint r1 = countbits(0b1);
+    uint2 r2 = countbits(uint2(0b0, 0b1));
+    uint3 r3 = countbits(uint3(0b0, 0b1, 0b11));
+    uint4 r4 = countbits(uint4(0b0, 0b1, 0b11, 0b111));
+
+    outputBuffer[0] = true
+        && (r1 == 1)
+        && (r2.x == 0 && r2.y == 1)
+        && (r3.x == 0 && r3.y == 1 && r3.z == 2)
+        && (r4.x == 0 && r4.y == 1 && r4.z == 2 && r4.w == 3)
+        ;
+}