Print warning when operator<< shifting too much (#4255)

* Print warning when operator<< shifting too much

Closes #3944

For the given type of the left side operand to `operator<<` is not big
enough for the right side operand, print a warning that the result will
be always zero.

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/diagnostics/warning_operator_left_shift_overflow.slang b/tests/diagnostics/warning_operator_left_shift_overflow.slang
new file mode 100644
index 000000000..5c156a9b9
--- /dev/null
+++ b/tests/diagnostics/warning_operator_left_shift_overflow.slang
@@ -0,0 +1,27 @@
+//TEST:SIMPLE(filecheck=CHECK): -stage compute -entry computeMain -target hlsl
+
+RWStructuredBuffer<int> inputBuffer;
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(int3 dispatchThreadID: SV_DispatchThreadID)
+{
+    uint8_t u8 = uint8_t(inputBuffer[0]);
+
+    uint result = (u8 << 0)
+        + (u8 << 1)
+        + (u8 << 2)
+        + (u8 << 3)
+        + (u8 << 4)
+        + (u8 << 5)
+        + (u8 << 6)
+        + (u8 << 7)
+        // CHECK-NOT: warning 41030:
+        // CHECK: ([[#@LINE+1]]): warning 41030: {{.*}}uint8{{.*}}8
+        + (u8 << 8)
+        // CHECK: ([[#@LINE+1]]): warning 41030: {{.*}}uint8{{.*}}9
+        + (u8 << 9)
+        ;
+
+    outputBuffer[0] = int(result);
+}