[MIPS GlobalISel] Combine extending loads

Use CombinerHelper to combine extending load instructions.
G_LOAD combined with G_ZEXT, G_SEXT or G_ANYEXT gives G_ZEXTLOAD,
G_SEXTLOAD or G_LOAD with same type as def of extending instruction
respectively.
Similarly G_ZEXTLOAD combined with G_ZEXT gives G_ZEXTLOAD and
G_SEXTLOAD combined with G_SEXT gives G_SEXTLOAD with same type
as def of extending instruction.

Differential Revision: https://reviews.llvm.org/D56914

llvm-svn: 352037

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsPreLegalizerCombiner.cpp b/llvm/lib/Target/Mips/MipsPreLegalizerCombiner.cpp
index 243a0dae944..85076590d40 100644
--- a/llvm/lib/Target/Mips/MipsPreLegalizerCombiner.cpp
+++ b/llvm/lib/Target/Mips/MipsPreLegalizerCombiner.cpp
@@ -13,6 +13,7 @@
 
 #include "MipsTargetMachine.h"
 #include "llvm/CodeGen/GlobalISel/Combiner.h"
+#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
 #include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
 #include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
@@ -34,6 +35,16 @@ public:
 bool MipsPreLegalizerCombinerInfo::combine(GISelChangeObserver &Observer,
                                            MachineInstr &MI,
                                            MachineIRBuilder &B) const {
+  CombinerHelper Helper(Observer, B);
+
+  switch (MI.getOpcode()) {
+  default:
+    return false;
+  case TargetOpcode::G_LOAD:
+  case TargetOpcode::G_SEXTLOAD:
+  case TargetOpcode::G_ZEXTLOAD:
+    return Helper.tryCombineExtendingLoads(MI);
+  }
   return false;
 }