From c6132508b1e11a76d24cbb744b452775a686fdae Mon Sep 17 00:00:00 2001
From: Martin <noone@nowhere.com>
Date: Sun, 11 Feb 2018 15:14:18 +0100
Subject: [PATCH] Don't waste an alloca for the nested context argument

And so get rid of all loads too; just use the untouched pointer argument
directly.
---
 gen/functions.cpp |  5 -----
 gen/nested.cpp    |  9 +++------
 gen/toir.cpp      | 11 +++++------
 3 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/gen/functions.cpp b/gen/functions.cpp
index be326938af..ad56713401 100644
--- a/gen/functions.cpp
+++ b/gen/functions.cpp
@@ -1098,11 +1098,6 @@ void DtoDefineFunction(FuncDeclaration *fd, bool linkageAvailableExternally) {
     gIR->DBuilder.EmitLocalVariable(thismem, fd->vthis, nullptr, true);
   }
 
-  // give the 'nestArg' parameter (an lvalue) storage
-  if (irFty.arg_nest) {
-    irFunc->nestArg = DtoAllocaDump(irFunc->nestArg, 0, "nestedFrame");
-  }
-
   // define all explicit parameters
   if (fd->parameters)
     defineParameters(irFty, *fd->parameters);
diff --git a/gen/nested.cpp b/gen/nested.cpp
index 9cd813fc86..ae6116347f 100644
--- a/gen/nested.cpp
+++ b/gen/nested.cpp
@@ -75,9 +75,8 @@ DValue *DtoNestedVariable(Loc &loc, Type *astype, VarDeclaration *vd,
     ctx = DtoLoad(DtoGEPi(val, 0, getVthisIdx(cd), ".vthis"));
     skipDIDeclaration = true;
   } else {
-    Logger::println("Regular nested function, loading context arg");
-
-    ctx = DtoLoad(irfunc->nestArg);
+    Logger::println("Regular nested function, using context arg");
+    ctx = irfunc->nestArg;
   }
 
   assert(ctx);
@@ -224,7 +223,7 @@ LLValue *DtoNestedContext(Loc &loc, Dsymbol *sym) {
     fromParent = false;
   } else if (irFunc.nestArg) {
     // otherwise, it may have gotten a context from the caller
-    val = DtoLoad(irFunc.nestArg);
+    val = irFunc.nestArg;
   } else if (irFunc.thisArg) {
     // or just have a this argument
     AggregateDeclaration *ad = irFunc.decl->isMember2();
@@ -456,8 +455,6 @@ void DtoCreateNestedContext(FuncGenState &funcGen) {
         } else {
           src = DtoLoad(DtoGEPi(thisval, 0, getVthisIdx(cd), ".vthis"));
         }
-      } else {
-        src = DtoLoad(src);
       }
       if (depth > 1) {
         src = DtoBitCast(src, getVoidPtrType());
diff --git a/gen/toir.cpp b/gen/toir.cpp
index 60dd2fd490..de42d91f5d 100644
--- a/gen/toir.cpp
+++ b/gen/toir.cpp
@@ -1021,20 +1021,19 @@ public:
     assert(!isSpecialRefVar(vd) && "Code not expected to handle special ref "
                                    "vars, although it can easily be made to.");
 
-    LLValue *v;
     const auto ident = p->func()->decl->ident;
     if (ident == Id::ensure || ident == Id::require) {
       Logger::println("contract this exp");
-      v = DtoBitCast(p->func()->nestArg, DtoType(e->type)->getPointerTo());
+      LLValue *v = DtoBitCast(p->func()->nestArg, DtoType(e->type));
+      result = new DImValue(e->type, v);
     } else if (vd->toParent2() != p->func()->decl) {
       Logger::println("nested this exp");
       result = DtoNestedVariable(e->loc, e->type, vd, e->type->ty == Tstruct);
-      return;
     } else {
       Logger::println("normal this exp");
-      v = p->func()->thisArg;
+      LLValue *v = p->func()->thisArg;
+      result = new DLValue(e->type, DtoBitCast(v, DtoPtrToType(e->type)));
     }
-    result = new DLValue(e->type, DtoBitCast(v, DtoPtrToType(e->type)));
   }
 
   //////////////////////////////////////////////////////////////////////////////
@@ -2184,7 +2183,7 @@ public:
         // function. Happens with anonymous functions.
         cval = funcGen.nestedVar;
       } else if (irfn.nestArg) {
-        cval = DtoLoad(irfn.nestArg);
+        cval = irfn.nestArg;
       } else if (irfn.thisArg) {
         AggregateDeclaration *ad = irfn.decl->isMember2();
         if (!ad || !ad->vthis) {