[FastISel][AArch64 and X86] Don't emit stores for UNDEF arguments during function call lowering.

UNDEF arguments are not ment to be touched - especially for the webkit_js
calling convention. This fix reproduces the already existing behavior of
SelectionDAG in FastISel.

llvm-svn: 214366

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index 52e65670a50..0938eda9dad 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -2831,6 +2831,11 @@ bool X86FastISel::FastLowerCall(CallLoweringInfo &CLI) {
       OutRegs.push_back(VA.getLocReg());
     } else {
       assert(VA.isMemLoc());
+
+      // Don't emit stores for undef values.
+      if (isa<UndefValue>(ArgVal))
+        continue;
+
       unsigned LocMemOffset = VA.getLocMemOffset();
       X86AddressMode AM;
       AM.Base.Reg = RegInfo->getStackRegister();