irgen: don't emit debug metadata for locals

[axw]

Summary

The debug metadata we generate is wrong, and is
now causing build failures. This revision disables
the only llvm.dbg.declare calls we make.

(There is also a drive-by fix to CMakeLists.txt,
adding in a missing .go dependency.)

Fixes http://llvm.org/bugs/show_bug.cgi?id=22330

[pcc]

LGTM

[dblaikie]

(might be useful to include [llgo] or something similar in the subject line
in the future to help reviewers filter/prioritize appropriately - took me a
moment to realize this wasn't something I needed to worry about)

[axw]

In D7222#114766, @dblaikie wrote:

(might be useful to include [llgo] or something similar in the subject line
in the future to help reviewers filter/prioritize appropriately - took me a
moment to realize this wasn't something I needed to worry about)

Will do, sorry for the noise.

CMakeLists.txt

llvm_add_go_executable(llgo llvm.org/llgo/cmd/gllgo ALL DEPENDS
   irgen/interfaces.go
   irgen/maps.go
   irgen/predicates.go
   irgen/println.go
   irgen/runtime.go
   irgen/slice.go
   irgen/ssa.go
   irgen/strings.go
+  irgen/switches.go
   irgen/targets.go
   irgen/typemap.go
   irgen/types.go
   irgen/utils.go
   irgen/value.go
   irgen/version.go
   ssaopt/esc.go
 )

irgen/ssa.go

for i, block := range f.Blocks {
     fr.blocks[i] = llvm.AddBasicBlock(fr.function, fmt.Sprintf(".%d.%s", i, block.Comment))
   }
   fr.builder.SetInsertPointAtEnd(fr.blocks[0])
   fr.transformSwitches(f)
 
   prologueBlock := llvm.InsertBasicBlock(fr.blocks[0], "prologue")
   fr.builder.SetInsertPointAtEnd(prologueBlock)
 
-  // Map parameter positions to indices. We use this
-  // when processing locals to map back to parameters
-  // when generating debug metadata.
-  paramPos := make(map[token.Pos]int)
   for i, param := range f.Params {
-    paramPos[param.Pos()] = i
     llparam := fti.argInfos[i].decode(llvm.GlobalContext(), fr.builder, fr.builder)
     if isMethod && i == 0 {
       if _, ok := param.Type().Underlying().(*types.Pointer); !ok {
         llparam = fr.builder.CreateBitCast(llparam, llvm.PointerType(fr.types.ToLLVM(param.Type()), 0), "")
         llparam = fr.builder.CreateLoad(llparam, "")
       }
     }
     fr.env[param] = newValue(llparam, param.Type())
func (u *unit) defineFunction(f *ssa.Function) {
   // Allocate stack space for locals in the prologue block.
   for _, local := range f.Locals {
     typ := fr.llvmtypes.ToLLVM(deref(local.Type()))
     alloca := fr.builder.CreateAlloca(typ, local.Comment)
     fr.memsetZero(alloca, llvm.SizeOf(typ))
     bcalloca := fr.builder.CreateBitCast(alloca, llvm.PointerType(llvm.Int8Type(), 0), "")
     value := newValue(bcalloca, local.Type())
     fr.env[local] = value
-    if fr.GenerateDebug {
-      paramIndex, ok := paramPos[local.Pos()]
-      if !ok {
-        paramIndex = -1
-      }
-      fr.debug.Declare(fr.builder, local, alloca, paramIndex)
-    }
   }
 
   // If the function contains any defers, we must first create
   // an unwind block. We can short-circuit the check for defers with
   // f.Recover != nil.
   if f.Recover != nil || hasDefer(f) {
     fr.unwindBlock = llvm.AddBasicBlock(fr.function, "")
     fr.frameptr = fr.builder.CreateAlloca(llvm.Int8Type(), "")