From: Alex Bradbury <asb@lowrisc.org>
Date: Wed, 11 Oct 2017 13:48:45 +0000 (+0000)
Subject: [TargetLowering] Correctly track NumFixedArgs field of CallLoweringInfo
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a951eff6275ed7f66448d265de5abcc1ca669e29;p=llvm

[TargetLowering] Correctly track NumFixedArgs field of CallLoweringInfo

The NumFixedArgs field of CallLoweringInfo is used by
TargetLowering::LowerCallTo to determine whether a given argument is passed
using the vararg calling convention or not (specifically, to set IsFixed for
each ISD::OutputArg).

Firstly, CallLoweringInfo::setLibCallee and CallLoweringInfo::setCallee both
incorrectly set NumFixedArgs based on the _previous_ args list. Secondly,
TargetLowering::LowerCallTo failed to increment NumFixedArgs when modifying
the argument list so a pointer is passed for the return value.

If your backend uses the IsFixed property or directly accesses NumFixedArgs,
it is _possible_ this change could result in codegen changes (although the
previous behaviour would have been incorrect). No such cases have been
identified during code review for any in-tree architecture.

Differential Revision: https://reviews.llvm.org/D37898


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315457 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index ea3e3f7b049..d35acdfc92e 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -2907,7 +2907,7 @@ public:
       RetTy = ResultType;
       Callee = Target;
       CallConv = CC;
-      NumFixedArgs = Args.size();
+      NumFixedArgs = ArgsList.size();
       Args = std::move(ArgsList);
 
       DAG.getTargetLoweringInfo().markLibCallAttributes(
@@ -2920,7 +2920,7 @@ public:
       RetTy = ResultType;
       Callee = Target;
       CallConv = CC;
-      NumFixedArgs = Args.size();
+      NumFixedArgs = ArgsList.size();
       Args = std::move(ArgsList);
       return *this;
     }
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index df49b0474f3..75641e05648 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -8077,6 +8077,7 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
     Entry.IsSwiftError = false;
     Entry.Alignment = Align;
     CLI.getArgs().insert(CLI.getArgs().begin(), Entry);
+    CLI.NumFixedArgs += 1;
     CLI.RetTy = Type::getVoidTy(CLI.RetTy->getContext());
 
     // sret demotion isn't compatible with tail-calls, since the sret argument