Fix a bug in IR linking (#777)

The IR linking logic was recently rewritten to use the (optional) `IRLinkageDecoration`s instead of assuming `IRGlobalVals` always have a mangled name field, and in that process a bug seems to have crept in where in the case that an instruction that would usually quality as a "global value" does *not* have linkage, we were failing to register the instruction we create in the output module as a replacement for the original instruction.

This problem affects `static` variables inside of functions, leading to them potentially getting emitted multiple times.

2 files changed, 26 insertions, 0 deletions

diff --git a/tests/bugs/static-var.slang b/tests/bugs/static-var.slang
new file mode 100644
index 000000000..f060586ad
--- /dev/null
+++ b/tests/bugs/static-var.slang
@@ -0,0 +1,22 @@
+// gh-775-ext.slang
+//TEST(compute):COMPARE_COMPUTE:
+
+int test(int inVal)
+{
+    static int kVal = 16;
+    return inVal + kVal;
+}
+
+//TEST_INPUT:ubuffer(data=[9 9 9 9], stride=4):dxbinding(0),glbinding(0),out
+RWStructuredBuffer<int> outputBuffer : register(u0);
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+	uint tid = dispatchThreadID.x;
+
+	int inVal = int(tid);
+	int outVal = test(inVal);
+
+	outputBuffer[tid] = outVal;
+}
\ No newline at end of file
diff --git a/tests/bugs/static-var.slang.expected.txt b/tests/bugs/static-var.slang.expected.txt
new file mode 100644
index 000000000..a0d427709
--- /dev/null
+++ b/tests/bugs/static-var.slang.expected.txt
@@ -0,0 +1,4 @@
+10
+11
+12
+13