[X86] Support cleaning more than 2**16 bytes of stack

The x86 ret instruction has a 16 bit immediate indicating how many bytes
to pop off of the stack beyond the return address.

There is a problem when extremely large structs are passed by value: we
might not be able to fit the number of bytes to pop into the return
instruction.

To fix this, expand RET_FLAG a little later and use a special sequence
to clean the stack:

pop  %ecx     ; return address is now in %ecx
add  $n, %esp ; clean the stack
push %ecx     ; bring the return address back on the stack
ret           ; pop the return address and jmp to it's value

llvm-svn: 262755

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 2a11eddaf15..65b8fb88b6d 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -2211,7 +2211,7 @@ X86TargetLowering::LowerReturn(SDValue Chain,
   RetOps.push_back(Chain); // Operand #0 = Chain (updated below)
   // Operand #1 = Bytes To Pop
   RetOps.push_back(DAG.getTargetConstant(FuncInfo->getBytesToPopOnReturn(), dl,
-                   MVT::i16));
+                   MVT::i32));
 
   // Copy the result values into the output registers.
   for (unsigned i = 0, e = RVLocs.size(); i != e; ++i) {