Register LLVM passes with the correct LLVM pass manager.

LLVM was upgraded to a new version in this commit:

f9d4149c29

which was part of this pull request:

https://github.com/rust-lang/rust/issues/26025

Consider the following two lines from that commit:

f9d4149c29 (diff-a3b24dbe2ea7c1981f9ac79f9745f40aL462)

f9d4149c29 (diff-a3b24dbe2ea7c1981f9ac79f9745f40aL469)

The purpose of these lines is to register LLVM passes. Prior to the that
commit, the passes being handled were assumed to be ModulePasses (a
specific type of LLVM pass) since they were being added to a ModulePass
manager. After that commit, both lines were refactored (presumably in an
attempt to DRY out the code), but the ModulePasses were changed to be
registered to a FunctionPass manager. This change resulted in
ModulePasses being run, but a Function object was being passed as a
parameter to the pass instead of a Module, which resulted in
segmentation faults.

In this commit, I changed relevant sections of the code to check the
type of the passes being added and register them to the appropriate pass
manager.

Closes https://github.com/rust-lang/rust/issues/31067

src/rustllvm/PassWrapper.cpp

@@ -58,19 +58,43 @@ LLVMInitializePasses() {
   initializeTarget(Registry);
 }
 
-extern "C" bool
-LLVMRustAddPass(LLVMPassManagerRef PM, const char *PassName) {
-    PassManagerBase *pm = unwrap(PM);
 
+enum class SupportedPassKind {
+  Function,
+  Module,
+  Unsupported
+};
+
+extern "C" Pass*
+LLVMRustFindAndCreatePass(const char *PassName) {
     StringRef SR(PassName);
     PassRegistry *PR = PassRegistry::getPassRegistry();
 
     const PassInfo *PI = PR->getPassInfo(SR);
     if (PI) {
-        pm->add(PI->createPass());
-        return true;
+        return PI->createPass();
     }
-    return false;
+    return NULL;
+}
+
+extern "C" SupportedPassKind
+LLVMRustPassKind(Pass *pass) {
+    assert(pass);
+    PassKind passKind = pass->getPassKind();
+    if (passKind == PT_Module) {
+        return SupportedPassKind::Module;
+    } else if (passKind == PT_Function) {
+        return SupportedPassKind::Function;
+    } else {
+        return SupportedPassKind::Unsupported;
+    }
+}
+
+extern "C" void
+LLVMRustAddPass(LLVMPassManagerRef PM, Pass *pass) {
+    assert(pass);
+    PassManagerBase *pm = unwrap(PM);
+    pm->add(pass);
 }
 
 extern "C" LLVMTargetMachineRef