[ARM] GlobalISel: Load i1, i8 and i16 args from stack

Add support for loading i1, i8 and i16 arguments from the stack, with or without
the ABI extension flags.

When the ABI extension flags are present, we load a 4-byte value, otherwise we
preserve the size of the load and let the instruction selector replace it with a
LDRB/LDRH. This generates the same thing as DAGISel.

Differential Revision: https://reviews.llvm.org/D27803

llvm-svn: 293163

1 files changed, 12 insertions, 11 deletions

diff --git a/llvm/lib/Target/ARM/ARMCallLowering.cpp b/llvm/lib/Target/ARM/ARMCallLowering.cpp
index dcd26341db0..5a2ded2e4b7 100644
--- a/llvm/lib/Target/ARM/ARMCallLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMCallLowering.cpp
@@ -122,7 +122,7 @@ struct FormalArgHandler : public CallLowering::ValueHandler {
 
   unsigned getStackAddress(uint64_t Size, int64_t Offset,
                            MachinePointerInfo &MPO) override {
-    assert(Size == 4 && "Unsupported size");
+    assert((Size == 1 || Size == 2 || Size == 4) && "Unsupported size");
 
     auto &MFI = MIRBuilder.getMF().getFrameInfo();
 
@@ -138,7 +138,16 @@ struct FormalArgHandler : public CallLowering::ValueHandler {
 
   void assignValueToAddress(unsigned ValVReg, unsigned Addr, uint64_t Size,
                             MachinePointerInfo &MPO, CCValAssign &VA) override {
-    assert(Size == 4 && "Unsupported size");
+    assert((Size == 1 || Size == 2 || Size == 4) && "Unsupported size");
+
+    if (VA.getLocInfo() == CCValAssign::SExt ||
+        VA.getLocInfo() == CCValAssign::ZExt) {
+      // If the argument is zero- or sign-extended by the caller, its size
+      // becomes 4 bytes, so that's what we should load.
+      Size = 4;
+      assert(MRI.getType(ValVReg).isScalar() && "Only scalars supported atm");
+      MRI.setType(ValVReg, LLT::scalar(32));
+    }
 
     auto MMO = MIRBuilder.getMF().getMachineMemOperand(
         MPO, MachineMemOperand::MOLoad, Size, /* Alignment */ 0);
@@ -177,18 +186,10 @@ bool ARMCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
     return false;
 
   auto &Args = F.getArgumentList();
-  unsigned ArgIdx = 0;
-  for (auto &Arg : Args) {
-    ArgIdx++;
+  for (auto &Arg : Args)
     if (!isSupportedType(DL, TLI, Arg.getType()))
       return false;
 
-    // FIXME: This check as well as ArgIdx are going away as soon as we support
-    // loading values < 32 bits.
-    if (ArgIdx > 4 && Arg.getType()->getIntegerBitWidth() != 32)
-      return false;
-  }
-
   CCAssignFn *AssignFn =
       TLI.CCAssignFnForCall(F.getCallingConv(), F.isVarArg());