GC poses hazards to the inliner. Consider:

define void @f() {
            ...
            call i32 @g()
            ...
    }

    define void @g() {
            ...
    }

The hazards are:

  - @f and @g have GC, but they differ GC. Inlining is invalid. This
    may never occur.
  - @f has no GC, but @g does. g's GC must be propagated to @f.

The other scenarios are safe:

  - @f and @g have the same GC.
  - @f and @g have no GC.
  - @g has no GC.

This patch adds inliner checks for the former two scenarios.

llvm-svn: 45351

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -201,6 +201,19 @@ bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) {
   BasicBlock *OrigBB = TheCall->getParent();
   Function *Caller = OrigBB->getParent();
 
+  
+  // GC poses two hazards to inlining, which only occur when the callee has GC:
+  //  1. If the caller has no GC, then the callee's GC must be propagated to the
+  //     caller.
+  //  2. If the caller has a differing GC, it is invalid to inline.
+  if (CalledFunc->hasCollector()) {
+    if (!Caller->hasCollector())
+      Caller->setCollector(CalledFunc->getCollector());
+    else if (CalledFunc->getCollector() != Caller->getCollector())
+      return false;
+  }
+  
+  
   // Get an iterator to the last basic block in the function, which will have
   // the new function inlined after it.
   //

llvm/test/CodeGen/Generic/GC/inline.ll

@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | opt -inline | llvm-dis | grep example
+
+	%IntArray = type { i32, [0 x i32*] }
+
+declare void @llvm.gcroot(i8**, i8*) nounwind 
+
+define i32 @f() {
+	%x = call i32 @g( )		; <i32> [#uses=1]
+	ret i32 %x
+}
+
+define internal i32 @g() gc "example" {
+	%root = alloca i8*		; <i8**> [#uses=2]
+	call void @llvm.gcroot( i8** %root, i8* null )
+	%obj = call %IntArray* @h( )		; <%IntArray*> [#uses=2]
+	%obj.2 = bitcast %IntArray* %obj to i8*		; <i8*> [#uses=1]
+	store i8* %obj.2, i8** %root
+	%Length.ptr = getelementptr %IntArray* %obj, i32 0, i32 0		; <i32*> [#uses=1]
+	%Length = load i32* %Length.ptr		; <i32> [#uses=1]
+	ret i32 %Length
+}
+
+declare %IntArray* @h()

llvm/test/CodeGen/Generic/GC/inline2.ll

@@ -0,0 +1,24 @@
+; RUN: llvm-as < %s | opt -inline | llvm-dis | grep sample
+; RUN: llvm-as < %s | opt -inline | llvm-dis | grep example
+
+	%IntArray = type { i32, [0 x i32*] }
+
+declare void @llvm.gcroot(i8**, i8*) nounwind 
+
+define i32 @f() gc "sample" {
+	%x = call i32 @g( )		; <i32> [#uses=1]
+	ret i32 %x
+}
+
+define internal i32 @g() gc "example" {
+	%root = alloca i8*		; <i8**> [#uses=2]
+	call void @llvm.gcroot( i8** %root, i8* null )
+	%obj = call %IntArray* @h( )		; <%IntArray*> [#uses=2]
+	%obj.2 = bitcast %IntArray* %obj to i8*		; <i8*> [#uses=1]
+	store i8* %obj.2, i8** %root
+	%Length.ptr = getelementptr %IntArray* %obj, i32 0, i32 0		; <i32*> [#uses=1]
+	%Length = load i32* %Length.ptr		; <i32> [#uses=1]
+	ret i32 %Length
+}
+
+declare %IntArray* @h()