[IR] Abstract away ArgNo+1 attribute indexing as much as possible

Summary:
Do three things to help with that:
- Add AttributeList::FirstArgIndex, which is an enumerator currently set
  to 1. It allows us to change the indexing scheme with fewer changes.
- Add addParamAttr/removeParamAttr. This just shortens addAttribute call
  sites that would otherwise need to spell out FirstArgIndex.
- Remove some attribute-specific getters and setters from Function that
  take attribute list indices.  Most of these were only used from
  BuildLibCalls, and doesNotAlias was only used to test or set if the
  return value is malloc-like.

I'm happy to split the patch, but I think they are probably easier to
review when taken together.

This patch should be NFC, but it sets the stage to change the indexing
scheme to this, which is more convenient when indexing into an array:
  0: func attrs
  1: retattrs
  2...: arg attrs

Reviewers: chandlerc, pete, javed.absar

Subscribers: david2050, llvm-commits

Differential Revision: https://reviews.llvm.org/D32811

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302060 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGObjCGNU.cpp b/lib/CodeGen/CGObjCGNU.cpp
index 9f6ccb4b5d2660539b25628d2da4332a127fd092..821629c50d4a1e00d8c796c2e42c0b8d7c0751e4 100644 (file)
--- a/lib/CodeGen/CGObjCGNU.cpp
+++ b/lib/CodeGen/CGObjCGNU.cpp
@@ -663,7 +663,7 @@ class CGObjCGNUstep : public CGObjCGNU {
       }
 
       // The lookup function is guaranteed not to capture the receiver pointer.
-      LookupFn->setDoesNotCapture(1);
+      LookupFn->addParamAttr(0, llvm::Attribute::NoCapture);
 
       llvm::Value *args[] = {
               EnforceType(Builder, ReceiverPtr.getPointer(), PtrToIdTy),