msvc style bitfield packing (#7963)

Closes https://github.com/shader-slang/slang/issues/3646

New tests rather than just adding another TEST line to existing tests so
that we get the msvc- prefix in the output of slang-test

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/language-feature/bitfield/msvc-simple.slang b/tests/language-feature/bitfield/msvc-simple.slang
new file mode 100644
index 000000000..4651626b8
--- /dev/null
+++ b/tests/language-feature/bitfield/msvc-simple.slang
@@ -0,0 +1,31 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK):-cpu -output-using-type -compile-arg -msvc-style-bitfield-packing
+
+// With MSVC packing, bitfields are packed from MSB to LSB
+// and new backing fields start when type sizes change
+// CHECK:      123
+// CHECK-NEXT: 4567
+// CHECK-NEXT: 0
+// CHECK-NEXT: 0
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<uint> outputBuffer;
+
+struct S {
+    int foo : 8;   // Packed in bits 31-24
+    uint bar : 24; // Packed in bits 23-0
+};
+
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    S s;
+    s.foo = 123;
+    s.bar = 4567;
+    outputBuffer[0] = s.foo;
+    outputBuffer[1] = s.bar;
+    s.foo = 0;
+    s.bar = 0;
+    outputBuffer[2] = s.foo;
+    outputBuffer[3] = s.bar;
+}
+