Implement throw & catch statements (#6916)

* Implement throw statement

It already existed in the IR, so only parsing, checking and lowering was
missing.

* Initial catch implementation

Likely very broken.

* Error out when catch() isn't last in scope

* Prevent accessing variables from scope preceding catch

As those may actually not be available at that point.

* Add IError and use it in Result type lowering

* Add diagnostic tests

* Allow caught throws in non-throw functions

* Fix catch propagating between functions & SPIR-V merge issue

* Add test for non-trivial error types

* Fix MSVC build

* Fix invalid value type from Result lowering

* Also lower error handling in templates

* Lower result types only after specialization

* Attempt to disambiguate error enums by witness table

* Revert matching by witness, types should be distinct too

* Don't assert valueField when getting Result's error value

It may not exist if the function returns void, but getting the error
value is still legitimate.

* Update tests for new error numbers & get rid of expected.txt

* Change catch lowering to resemble breaking a loop

... To make SPIR-V happy.

* Fix dead catch blocks and invalid cached dominator tree

* More SPIR-V adjustment

* Lower catch as two nested loops

* Add defer interaction test and revert broken defer changes

* Fix enum type when throwing literals

* Cleanup and bikeshedding

* Document error handling mechanism

* Fix table of contents

* Use boolean tag in Result<T, E>

* Use anyValue storage for Result<T,E>

* Remove IError

* Fix formatting

* Eradicate success values from docs and tests

* Use parseModernParamDecl for catch parameter

* Implement do-catch syntax

* Implement catch-all

* Fix formatting

* Fix marshalling native calls that throw

---------

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

1 files changed, 91 insertions, 0 deletions

diff --git a/tests/language-feature/error-handling/basic.slang b/tests/language-feature/error-handling/basic.slang
new file mode 100644
index 000000000..4cb270cb8
--- /dev/null
+++ b/tests/language-feature/error-handling/basic.slang
@@ -0,0 +1,91 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -vk -shaderobj
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -cpu -shaderobj
+
+// CHECK: 2
+// CHECK-NEXT: 0
+// CHECK-NEXT: 11
+// CHECK-NEXT: 12
+// CHECK-NEXT: 6
+// CHECK-NEXT: 1
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+enum MyError1
+{
+    Fail
+};
+
+enum MyError2
+{
+    Fail1,
+    Fail2 = 0x12
+};
+
+void throwingFunc() throws MyError1
+{
+    throw MyError1.Fail;
+}
+
+int maybeBadFunc1(int n) throws MyError1
+{
+    if (n == 1) throw MyError1.Fail;
+    return n;
+}
+
+int maybeBadFunc2(int n) throws MyError2
+{
+    if (n == 2) throw MyError2.Fail2;
+    return n;
+}
+
+int multiCatchFunc(int n)
+{
+    do
+    {
+        let a = try maybeBadFunc1(n);
+        let b = try maybeBadFunc2(n);
+        return a+b;
+    }
+    catch(err: MyError1)
+    {
+        return 0x11;
+    }
+    catch(err: MyError2)
+    {
+        return reinterpret<int>(err);
+    }
+}
+
+int containedThrow()
+{
+    do
+    {
+        throw MyError1.Fail;
+    }
+    catch(err: MyError1)
+    {
+        return 1;
+    }
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(int3 dispatchThreadID: SV_DispatchThreadID)
+{
+    do
+    {
+        try throwingFunc();
+        outputBuffer[0] = 1;
+    }
+    catch(err: MyError1)
+    {
+        outputBuffer[0] = 2;
+    }
+
+    outputBuffer[1] = multiCatchFunc(0);
+    outputBuffer[2] = multiCatchFunc(1);
+    outputBuffer[3] = multiCatchFunc(2);
+    outputBuffer[4] = multiCatchFunc(3);
+    outputBuffer[5] = containedThrow();
+}