From 93a4a7fe0d7f25ccd66b64f7cc0c9dc746a0908f Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Wed, 6 May 2015 02:36:31 +0000
Subject: [PATCH] [Statepoint] Clean up StatepointLowering: symbolic constants.

For accessors in the `Statepoint` class, use symbolic constants for
offsets into the argument vector instead of literals.  This makes the
code intent clearer and simpler to change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236566 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/IR/Statepoint.h                  | 45 +++++++++----------
 .../SelectionDAG/StatepointLowering.cpp       |  5 ++-
 2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/include/llvm/IR/Statepoint.h b/include/llvm/IR/Statepoint.h
index ee9f7b9f1cd..a337222e08e 100644
--- a/include/llvm/IR/Statepoint.h
+++ b/include/llvm/IR/Statepoint.h
@@ -63,11 +63,19 @@ protected:
 public:
   typedef typename CallSiteTy::arg_iterator arg_iterator;
 
+  enum {
+    ActualCalleePos = 0,
+    NumCallArgsPos = 1,
+    CallArgsBeginPos = 3,
+  };
+
   /// Return the underlying CallSite.
   CallSiteTy getCallSite() { return StatepointCS; }
 
   /// Return the value actually being called or invoked.
-  ValueTy *getActualCallee() { return StatepointCS.getArgument(0); }
+  ValueTy *getActualCallee() {
+    return StatepointCS.getArgument(ActualCalleePos);
+  }
 
   /// Return the type of the value returned by the call underlying the
   /// statepoint.
@@ -79,26 +87,16 @@ public:
 
   /// Number of arguments to be passed to the actual callee.
   int getNumCallArgs() {
-    return cast<ConstantInt>(StatepointCS.getArgument(1))->getZExtValue();
+    const Value *NumCallArgsVal = StatepointCS.getArgument(NumCallArgsPos);
+    return cast<ConstantInt>(NumCallArgsVal)->getZExtValue();
   }
 
-  /// Number of additional arguments excluding those intended
-  /// for garbage collection.
-  int getNumTotalVMSArgs() {
-    const Value *NumVMSArgs = StatepointCS.getArgument(3 + getNumCallArgs());
-    return cast<ConstantInt>(NumVMSArgs)->getZExtValue();
-  }
-
-  int callArgsBeginOffset() { return 3; }
-
   typename CallSiteTy::arg_iterator call_args_begin() {
-    // 3 = callTarget, #callArgs, flag
-    int Offset = callArgsBeginOffset();
-    assert(Offset <= (int)StatepointCS.arg_size());
-    return StatepointCS.arg_begin() + Offset;
+    assert(CallArgsBeginPos <= (int)StatepointCS.arg_size());
+    return StatepointCS.arg_begin() + CallArgsBeginPos;
   }
   typename CallSiteTy::arg_iterator call_args_end() {
-    int Offset = callArgsBeginOffset() + getNumCallArgs();
+    int Offset = CallArgsBeginPos + getNumCallArgs();
     assert(Offset <= (int)StatepointCS.arg_size());
     return StatepointCS.arg_begin() + Offset;
   }
@@ -108,9 +106,16 @@ public:
     return iterator_range<arg_iterator>(call_args_begin(), call_args_end());
   }
 
+  /// Number of additional arguments excluding those intended
+  /// for garbage collection.
+  int getNumTotalVMSArgs() {
+    Value *NumVMSArgs = *call_args_end();
+    return cast<ConstantInt>(NumVMSArgs)->getZExtValue();
+  }
+
   typename CallSiteTy::arg_iterator vm_state_begin() { return call_args_end(); }
   typename CallSiteTy::arg_iterator vm_state_end() {
-    int Offset = 3 + getNumCallArgs() + 1 + getNumTotalVMSArgs();
+    int Offset = CallArgsBeginPos + getNumCallArgs() + 1 + getNumTotalVMSArgs();
     assert(Offset <= (int)StatepointCS.arg_size());
     return StatepointCS.arg_begin() + Offset;
   }
@@ -120,12 +125,6 @@ public:
     return iterator_range<arg_iterator>(vm_state_begin(), vm_state_end());
   }
 
-  typename CallSiteTy::arg_iterator first_vm_state_stack_begin() {
-    // 6 = numTotalVMSArgs, 1st_objectID, 1st_bci,
-    //     1st_#stack, 1st_#local, 1st_#monitor
-    return vm_state_begin() + 6;
-  }
-
   typename CallSiteTy::arg_iterator gc_args_begin() { return vm_state_end(); }
   typename CallSiteTy::arg_iterator gc_args_end() {
     return StatepointCS.arg_end();
diff --git a/lib/CodeGen/SelectionDAG/StatepointLowering.cpp b/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
index 521e27334ff..49c08d977bc 100644
--- a/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
@@ -250,8 +250,9 @@ lowerCallFromStatepoint(ImmutableStatepoint ISP, MachineBasicBlock *LandingPad,
 
   SDValue ReturnValue, CallEndVal;
   std::tie(ReturnValue, CallEndVal) = Builder.lowerCallOperands(
-      ISP.getCallSite(), ISP.callArgsBeginOffset(), ISP.getNumCallArgs(),
-      ActualCallee, DefTy, LandingPad, false /* IsPatchPoint */);
+      ISP.getCallSite(), ImmutableStatepoint::CallArgsBeginPos,
+      ISP.getNumCallArgs(), ActualCallee, DefTy, LandingPad,
+      false /* IsPatchPoint */);
 
   SDNode *CallEnd = CallEndVal.getNode();