[llvm] [Xtensa] Implement base CallConvention. (PR #83280)

[Sergei Barannikov via llvm-commits]

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@@ -41,10 +41,273 @@ XtensaTargetLowering::XtensaTargetLowering(const TargetMachine &TM,
 
   setMinFunctionAlignment(Align(4));
 
+  setBooleanContents(ZeroOrOneBooleanContent);
+
+  // No sign extend instructions for i1
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setLoadExtAction(ISD::SEXTLOAD, VT, MVT::i1, Promote);
+    setLoadExtAction(ISD::ZEXTLOAD, VT, MVT::i1, Promote);
+    setLoadExtAction(ISD::EXTLOAD, VT, MVT::i1, Promote);
+  }
+
   // Compute derived properties from the register classes
   computeRegisterProperties(STI.getRegisterInfo());
 }
 
+//===----------------------------------------------------------------------===//
+// Calling conventions
+//===----------------------------------------------------------------------===//
+
+#include "XtensaGenCallingConv.inc"
+
+static bool CC_Xtensa_Custom(unsigned ValNo, MVT ValVT, MVT LocVT,
+                             CCValAssign::LocInfo LocInfo,
+                             ISD::ArgFlagsTy ArgFlags, CCState &State) {
+  static const MCPhysReg IntRegs[] = {Xtensa::A2, Xtensa::A3, Xtensa::A4,
+                                      Xtensa::A5, Xtensa::A6, Xtensa::A7};
+
+  if (ArgFlags.isByVal()) {
+    Align ByValAlign = ArgFlags.getNonZeroByValAlign();
+    unsigned ByValSize = ArgFlags.getByValSize();
+    if (ByValSize < 4) {
+      ByValSize = 4;
+    }
+    if (ByValAlign < Align(4)) {
+      ByValAlign = Align(4);
+    }
+    unsigned Offset = State.AllocateStack(ByValSize, ByValAlign);
+    State.addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
+    // Mark all unused registers as allocated to avoid misuse
+    // of such registers.
+    while (State.AllocateReg(IntRegs))
+      ;
+    return false;
+  }
+
+  // Promote i8 and i16
+  if (LocVT == MVT::i8 || LocVT == MVT::i16) {
+    LocVT = MVT::i32;
+    if (ArgFlags.isSExt())
+      LocInfo = CCValAssign::SExt;
+    else if (ArgFlags.isZExt())
+      LocInfo = CCValAssign::ZExt;
+    else
+      LocInfo = CCValAssign::AExt;
+  }
+
+  unsigned Reg;
+
+  Align OrigAlign = ArgFlags.getNonZeroOrigAlign();
+  bool needs64BitAlign = (ValVT == MVT::i32 && OrigAlign == Align(8));
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s-barannikov wrote:

Variables start with a capital letter.

https://github.com/llvm/llvm-project/pull/83280