Precompiled SPIR-V import support (#5048)

* Precompiled SPIR-V import support

Adds appropriate linkage and function declaration syntax
for SPIR-V functions that are declared, to be imported
from another SPIR-V module.

Unlike DXIL, stripping the Slang IR for a function down
to a declaration requires retaining a block of parameters,
as the function declaration must be emitted to SPIR-V
with the same parameters as a definition. Because that
thwarts the logic in Slang to tell the difference between
a declaration and definition, and explicit decoration is
introduced to explicitly mark functions which need to be
treated as declarations during emit phase.

Fixes #4992

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/library/export-library-generics.slang b/tests/library/export-library-generics.slang
index f88541da3..3f17e0664 100644
--- a/tests/library/export-library-generics.slang
+++ b/tests/library/export-library-generics.slang
@@ -33,7 +33,7 @@ public int normalFuncUsesGeneric(int a)
     return genericFunc(obj);
 }
 
-public int normalFunc(int a)
+public int normalFunc(int a, float b)
 {
-    return a - 2;
+    return a - floor(b);
 }