GlobalISel: combine extracts & sequences created for legalization

Legalization ends up creating many G_SEQUENCE/G_EXTRACT pairs which leads to
inefficient codegen (even for -O0), so add a quick pass over the function to
remove them again.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280155 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 7 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h b/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
index 24ab286b51f..aa08d4530cb 100644
--- a/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ b/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -293,6 +293,7 @@ public:
   /// Idxs[0] + N)` of \p Src and similarly for subsequent bit-indexes.
   ///
   /// \pre setBasicBlock or setMI must have been called.
+  /// \pre \p Indices must be in ascending order of bit position.
   ///
   /// \return a MachineInstrBuilder for the newly created instruction.
   MachineInstrBuilder buildExtract(ArrayRef<LLT> ResTys,
@@ -311,7 +312,7 @@ public:
   ///      destination register.
   /// \pre The bits defined by each Op (derived from index and scalar size) must
   ///      not overlap.
-  /// \pre Each source operand must have a
+  /// \pre \p Indices must be in ascending order of bit position.
   ///
   /// \return a MachineInstrBuilder for the newly created instruction.
   MachineInstrBuilder buildSequence(LLT ResTy, unsigned Res,
diff --git a/include/llvm/CodeGen/GlobalISel/MachineLegalizePass.h b/include/llvm/CodeGen/GlobalISel/MachineLegalizePass.h
index ccdc05a9623..eca06f4612b 100644
--- a/include/llvm/CodeGen/GlobalISel/MachineLegalizePass.h
+++ b/include/llvm/CodeGen/GlobalISel/MachineLegalizePass.h
@@ -26,6 +26,8 @@
 
 namespace llvm {
 
+class MachineRegisterInfo;
+
 class MachineLegalizePass : public MachineFunctionPass {
 public:
   static char ID;
@@ -55,6 +57,9 @@ public:
         MachineFunctionProperties::Property::Legalized);
   }
 
+  bool combineExtracts(MachineInstr &MI, MachineRegisterInfo &MRI,
+                       const TargetInstrInfo &TII);
+
   bool runOnMachineFunction(MachineFunction &MF) override;
 };
 } // End namespace llvm.