[MIPS MSA] Avoid some DAG combines for vector shifts

DAG combiner combines two shifts into shift + and with bitmask.
Avoid such combines for vectors since leaving two vector shifts
as they are produces better end results.

Differential Revision: https://reviews.llvm.org/D58225

llvm-svn: 354461

2 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index 103d1fcb44b..d69effb6224 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -1190,6 +1190,13 @@ bool MipsTargetLowering::isCheapToSpeculateCtlz() const {
   return Subtarget.hasMips32();
 }
 
+bool MipsTargetLowering::shouldFoldShiftPairToMask(const SDNode *N,
+                                                   CombineLevel Level) const {
+  if (N->getOperand(0).getValueType().isVector())
+    return false;
+  return true;
+}
+
 void
 MipsTargetLowering::LowerOperationWrapper(SDNode *N,
                                           SmallVectorImpl<SDValue> &Results,
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.h b/llvm/lib/Target/Mips/MipsISelLowering.h
index e25810c8741..3a9e61b97b4 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.h
+++ b/llvm/lib/Target/Mips/MipsISelLowering.h
@@ -284,6 +284,8 @@ class TargetRegisterClass;
 
     bool isCheapToSpeculateCttz() const override;
     bool isCheapToSpeculateCtlz() const override;
+    bool shouldFoldShiftPairToMask(const SDNode *N,
+                                   CombineLevel Level) const override;
 
     /// Return the register type for a given MVT, ensuring vectors are treated
     /// as a series of gpr sized integers.