[AMDGPU][AsmParser] Refine SMRD offset definitions.

- Fixes the type of default 8-bit offset operands.
- Adds a test for optional offsets.

This is effectively an NFC.

Reviewed By: dp

Differential Revision: https://reviews.llvm.org/D142231

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -1758,7 +1758,6 @@ class AMDGPUAsmParser : public MCTargetAsmParser {
   AMDGPUOperand::Ptr defaultSMRDOffset8() const;
   AMDGPUOperand::Ptr defaultSMEMOffset() const;
   AMDGPUOperand::Ptr defaultSMEMOffsetMod() const;
-  AMDGPUOperand::Ptr defaultSMRDLiteralOffset() const;
   AMDGPUOperand::Ptr defaultFlatOffset() const;
 
   OperandMatchResultTy parseOModOperand(OperandVector &Operands);
@@ -7970,7 +7969,7 @@ bool AMDGPUOperand::isSMRDLiteralOffset() const {
 }
 
 AMDGPUOperand::Ptr AMDGPUAsmParser::defaultSMRDOffset8() const {
-  return AMDGPUOperand::CreateImm(this, 0, SMLoc(), AMDGPUOperand::ImmTyOffset);
+  return AMDGPUOperand::CreateImm(this, 0, SMLoc(), AMDGPUOperand::ImmTyNone);
 }
 
 AMDGPUOperand::Ptr AMDGPUAsmParser::defaultSMEMOffset() const {
@@ -7982,10 +7981,6 @@ AMDGPUOperand::Ptr AMDGPUAsmParser::defaultSMEMOffsetMod() const {
                                   AMDGPUOperand::ImmTySMEMOffsetMod);
 }
 
-AMDGPUOperand::Ptr AMDGPUAsmParser::defaultSMRDLiteralOffset() const {
-  return AMDGPUOperand::CreateImm(this, 0, SMLoc(), AMDGPUOperand::ImmTyOffset);
-}
-
 AMDGPUOperand::Ptr AMDGPUAsmParser::defaultFlatOffset() const {
   return AMDGPUOperand::CreateImm(this, 0, SMLoc(), AMDGPUOperand::ImmTyOffset);
 }

llvm/test/MC/AMDGPU/smrd.s

@@ -11,6 +11,12 @@
 // Offset Handling
 //===----------------------------------------------------------------------===//
 
+// SP3 requires the immediate offset, but we allow to drop it for
+// compatibility reasons.
+s_load_dword s1, s[2:3]
+// GCN: s_load_dword s1, s[2:3], 0x0 ; encoding: [0x00,0x83,0x00,0xc0]
+// VI: s_load_dword s1, s[2:3], 0x0 ; encoding: [0x41,0x00,0x02,0xc0,0x00,0x00,0x00,0x00]
+
 s_load_dword s1, s[2:3], 0xfc
 // GCN: s_load_dword s1, s[2:3], 0xfc ; encoding: [0xfc,0x83,0x00,0xc0]
 // VI:	s_load_dword s1, s[2:3], 0xfc   ; encoding: [0x41,0x00,0x02,0xc0,0xfc,0x00,0x00,0x00]