[RISCV][GlobalISel] Select constant operands as immediates

2 files changed, 24 insertions, 7 deletions

diff --git a/backend/lib/CodeGen/GlobalISel/InstructionSelect.cpp b/backend/lib/CodeGen/GlobalISel/InstructionSelect.cpp
index 642e26f..31d880e 100644
--- a/backend/lib/CodeGen/GlobalISel/InstructionSelect.cpp
+++ b/backend/lib/CodeGen/GlobalISel/InstructionSelect.cpp
@@ -2,6 +2,7 @@
 
 #include "rcc/CodeGen/GlobalISel/InstructionSelect.h"
 
+#include "rcc/CodeGen/GlobalISel/Utils.h"
 #include "rcc/CodeGen/MachineBasicBlock.h"
 #include "rcc/CodeGen/MachineFunction.h"
 #include "rcc/CodeGen/MachineFunctionCloner.h"
@@ -240,8 +241,16 @@ Expected<MachinePassResult> InstructionSelect::runImplementation(MachineFunction
 
   for (std::size_t Index = 0; Index < Worklist.size(); ++Index) {
     MachineInstr *Instruction = Worklist[Index];
-    if (Instruction->parent() == nullptr)
-      return std::unexpected(passFailure("instruction selector lost its input instruction"));
+    if (Instruction == nullptr || Instruction->parent() == nullptr)
+      continue;
+    if (isTriviallyDead(*Instruction, Function.registerInfo(), Target)) {
+      auto Removed = eraseInstr(*Instruction, Function.registerInfo(), Target);
+      if (!Removed)
+        return std::unexpected(Removed.error());
+      Result.Changed = true;
+      Result.Changes.add(MachinePassChange::Instructions);
+      continue;
+    }
     const InstructionDescriptor *CurrentDescriptor =
         Target.instructionDescriptor(Instruction->opcode());
     if (CurrentDescriptor == nullptr)
diff --git a/backend/lib/CodeGen/MachineVerifier.cpp b/backend/lib/CodeGen/MachineVerifier.cpp
index 5a040b9..abccc56 100644
--- a/backend/lib/CodeGen/MachineVerifier.cpp
+++ b/backend/lib/CodeGen/MachineVerifier.cpp
@@ -838,7 +838,9 @@ private:
         return fail("reserved-register list contains invalid or duplicate entries");
     }
 
-    for (const VirtualRegisterInfo &Info : RegInfo.virtualRegisters()) {
+    const auto VirtualRegisters = RegInfo.virtualRegisters();
+    for (std::size_t Index = 0; Index < VirtualRegisters.size(); ++Index) {
+      const VirtualRegisterInfo &Info = VirtualRegisters[Index];
       if (Info.IsTombstone) {
         if (Info.Type || Info.Bank || Info.RegClass || !Info.AllocationHints.empty() ||
             Info.TargetFlags != 0) {
@@ -846,10 +848,16 @@ private:
         }
         continue;
       }
-      HasLiveVirtualRegister = true;
-      MissingVirtualType |= !Info.Type;
-      MissingVirtualBank |= !Info.Bank;
-      MissingVirtualClass |= !Info.RegClass;
+      auto Reg = Register::makeVirtual(Index);
+      if (!Reg)
+        return failWith("virtual register", Reg.error());
+      const auto Operands = RegInfo.regOperands(*Reg);
+      if (Operands.begin() != Operands.end()) {
+        HasLiveVirtualRegister = true;
+        MissingVirtualType |= !Info.Type;
+        MissingVirtualBank |= !Info.Bank;
+        MissingVirtualClass |= !Info.RegClass;
+      }
       if (Info.Type && !Info.Type->isValid())
         return fail("virtual register has an invalid LowLevelType");