Build is broken when optimization is turned off

[marijnh]

While building stage1/lib/libstd.so:

rustc: /home/marijn/prog/llvm/include/llvm/Support/Casting.h:194: typename llvm::cast_retty<To, From>::ret_type llvm::cast(const Y&) [with X = llvm::FrameIndexSDNode, Y = llvm::SDNode*, typename llvm::cast_retty<To, From>::ret_type = llvm::FrameIndexSDNode*]: Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
Stack dump:
0.  Running pass 'Function Pass Manager' on module 'rust_out'.
1.  Running pass 'X86 DAG->DAG Instruction Selection' on function '@_ZN3int6to_strE'
Aborted
make: *** [stage1/lib/libstd.so] Error 134
make: Target `all' not remade because of errors.
make: Leaving directory `/home/marijn/src/rust'

[msullivan]

Bisecting.

[msullivan]

117d21d is the commit that broke it.

[pcwalton]

Taking this; I believe I have an LLVM fix for it.

[pcwalton]

LLVM patch:

Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp    (revision 137913)
+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp    (working copy)
@@ -4957,11 +4957,16 @@
   }
   case Intrinsic::gcroot:
     if (GFI) {
-      const Value *Alloca = I.getArgOperand(0);
-      const Constant *TypeMap = cast<Constant>(I.getArgOperand(1));
+      const Value *Alloca = I.getArgOperand(0)->stripPointerCasts();
+      assert(isa<AllocaInst>(Alloca) && "First argument to gcroot() must be "
+             "an alloca or a bitcast of one!");

+      const Value *TypeMap = I.getArgOperand(1);
+      assert(isa<Constant>(TypeMap) && "Second argument to gcroot() must be "
+             "a constant!");
+
       FrameIndexSDNode *FI = cast<FrameIndexSDNode>(getValue(Alloca).getNode());
-      GFI->addStackRoot(FI->getIndex(), TypeMap);
+      GFI->addStackRoot(FI->getIndex(), cast<Constant>(TypeMap));
     }
     return 0;
   case Intrinsic::gcread:

[pcwalton]

Fix has been sent to espindola; leaving this open until it's upstreamed, but this isn't breaking the build any longer.

[marijnh]

This seems to have landed (I removed the patch when updating LLVM this week, and I can still build without optimize)