[AMDGPU] Truncate packed inline constant

[rampitec]

Summary

If a packed inline constant is sign extended it must be truncated
after the shift. I.e. a constant (0xH0000, 0xHBC00), will be represented
as 0xFFFFFFFFBC000000 in the IR because the immediate is sign extended
to 64 bit. After the value shifted right by 16 to use it in a low part
with op_sel_hi it becomes 0xFFFFFFFFBC00 and does not qualify as inline
constant any longer.

Fixed the error and added verification code. Without the fix and with
the verification bug is causing pk_max_f16_literal.ll to fail.

[kzhuravl]

LGTM.

lib/Target/AMDGPU/SIFoldOperands.cpp

if (MI->getDesc().TSFlags & SIInstrFlags::IsPacked) {
       unsigned Val = Mod.getImm();
       if ((Val & SISrcMods::OP_SEL_0) || !(Val & SISrcMods::OP_SEL_1))
         return false;
       // If upper part is all zero we do not need op_sel_hi.
       if (!isUInt<16>(Fold.ImmToFold)) {
         if (!(Fold.ImmToFold & 0xffff)) {
           Mod.setImm(Mod.getImm() | SISrcMods::OP_SEL_0);
           Mod.setImm(Mod.getImm() & ~SISrcMods::OP_SEL_1);
-          Old.ChangeToImmediate(Fold.ImmToFold >> 16);
+          Old.ChangeToImmediate((Fold.ImmToFold >> 16) & 0xffff);
           return true;
         }
         Mod.setImm(Mod.getImm() & ~SISrcMods::OP_SEL_1);
       }
     }
     Old.ChangeToImmediate(Fold.ImmToFold);
     return true;
   }

lib/Target/AMDGPU/SIInstrInfo.cpp

bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
   if (Desc.getOpcode() != AMDGPU::V_WRITELANE_B32
       && (isVOP1(MI) || isVOP2(MI) || isVOP3(MI) || isVOPC(MI) || isSDWA(MI))) {
     // Only look at the true operands. Only a real operand can use the constant
     // bus, and we don't want to check pseudo-operands like the source modifier
     // flags.
     const int OpIndices[] = { Src0Idx, Src1Idx, Src2Idx };
 
     unsigned ConstantBusCount = 0;
+    unsigned LiteralCount = 0;
 
     if (AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::imm) != -1)
       ++ConstantBusCount;
 
     unsigned SGPRUsed = findImplicitSGPRRead(MI);
     if (SGPRUsed != AMDGPU::NoRegister)
       ++ConstantBusCount;
 
     for (int OpIdx : OpIndices) {
       if (OpIdx == -1)
         break;
       const MachineOperand &MO = MI.getOperand(OpIdx);
       if (usesConstantBus(MRI, MO, MI.getDesc().OpInfo[OpIdx])) {
         if (MO.isReg()) {
           if (MO.getReg() != SGPRUsed)
             ++ConstantBusCount;
           SGPRUsed = MO.getReg();
         } else {
           ++ConstantBusCount;
+          ++LiteralCount;
         }
       }
     }
     if (ConstantBusCount > 1) {
       ErrInfo = "VOP* instruction uses the constant bus more than once";
       return false;
     }
+
+    if (isVOP3(MI) && LiteralCount) {
+      ErrInfo = "VOP3 instruction uses literal";
+      return false;
+    }
   }
 
   // Verify misc. restrictions on specific instructions.
   if (Desc.getOpcode() == AMDGPU::V_DIV_SCALE_F32 ||
       Desc.getOpcode() == AMDGPU::V_DIV_SCALE_F64) {
     const MachineOperand &Src0 = MI.getOperand(Src0Idx);
     const MachineOperand &Src1 = MI.getOperand(Src1Idx);
     const MachineOperand &Src2 = MI.getOperand(Src2Idx);

test/CodeGen/AMDGPU/pk_max_f16_literal.ll

bb:
   %tmp2 = getelementptr inbounds <2 x half>, <2 x half> addrspace(1)* %arg, i64 %tmp1
   %tmp3 = load <2 x half>, <2 x half> addrspace(1)* %tmp2, align 4
   %tmp4 = tail call <2 x half> @llvm.maxnum.v2f16(<2 x half> %tmp3, <2 x half> <half 0xH3C00, half 0xH3C00>)
   store <2 x half> %tmp4, <2 x half> addrspace(1)* %tmp2, align 4
   ret void
 }
 
 ; GCN-LABEL: {{^}}test_pk_max_f16_literal_0_m1:
-; GFX9: v_pk_max_f16 v{{[0-9]+}}, -1.0, v{{[0-9]+}} op_sel:[1,0] op_sel_hi:[0,1]{{$}}
+; GFX9: v_pk_max_f16 v{{[0-9]+}}, v{{[0-9]+}}, -1.0 op_sel:[0,1] op_sel_hi:[1,0]{{$}}
 define amdgpu_kernel void @test_pk_max_f16_literal_0_m1(<2 x half> addrspace(1)* nocapture %arg) {
 bb:
   %tmp = tail call i32 @llvm.amdgcn.workitem.id.x()
   %tmp1 = zext i32 %tmp to i64
   %tmp2 = getelementptr inbounds <2 x half>, <2 x half> addrspace(1)* %arg, i64 %tmp1
   %tmp3 = load <2 x half>, <2 x half> addrspace(1)* %tmp2, align 4
   %tmp4 = tail call <2 x half> @llvm.maxnum.v2f16(<2 x half> %tmp3, <2 x half> <half 0xH0000, half 0xHBC00>)
   store <2 x half> %tmp4, <2 x half> addrspace(1)* %tmp2, align 4