Running opt -indvars on the attached LLVM code (once compiled to assembly)
aborts with the following message:

PHI nodes not grouped at top of basic block!
        %doinner.1.i = phi int [ 0, %then.3.i ], [ 0, %endif.0.i ]             
; <int> [#uses=0]
label %endif.3.i
Broken module found, compilation aborted!
opt[0x85bc2c2]
opt[0x85bc4e2]
opt[0x42029188]
opt(abort+0x16e)[0x4202a8c2]
opt((anonymous namespace)::Verifier::abortIfBroken() const+0x31)[0x85b1eef]
opt((anonymous namespace)::Verifier::runOnFunction(llvm::Function&)+0x4a)[0x85b1282]
opt(llvm::PassManagerTraits<llvm::Function>::runPass(llvm::FunctionPass*,
llvm::Function*)+0x1f)[0x8595577]
opt(llvm::PassManagerT<llvm::Function>::runOnUnit(llvm::Function*)+0x5c9)[0x858b9af]
opt(llvm::PassManagerTraits<llvm::Function>::runOnFunction(llvm::Function&)+0x1f)[0x858c589]
opt(llvm::FunctionPass::run(llvm::Module&)+0xa7)[0x854aa2b]
opt(llvm::PassManagerTraits<llvm::Module>::runPass(llvm::Pass*,
llvm::Module*)+0x1f)[0x859560d]
opt(llvm::PassManagerT<llvm::Module>::runOnUnit(llvm::Module*)+0x5c9)[0x8589b21]
opt(llvm::PassManagerTraits<llvm::Module>::run(llvm::Module&)+0x1f)[0x858b1c9]
opt(llvm::PassManager::run(llvm::Module&)+0x23)[0x8549eef]
opt(main+0x7c9)[0x8377da9]
opt(__libc_start_main+0x95)[0x42017589]
opt(dlopen+0x41)[0x8377531]
Abort (core dumped)

Created an attachment (id=96) [details]
LLVM assembly code that reproduces the problem

This was reduced by bugpoint from mi_arc.c from the GNU plotutils.

Fixed.  Patch here:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040308/012948.html

Testcase here:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040308/012947.html

Thanks for finding this John!

-Chris