Avoid copies of std::strings and APInt/APFloats where we only read from it

As suggested by clang-tidy's performance-unnecessary-copy-initialization.
This can easily hit lifetime issues, so I audited every change and ran the
tests under asan, which came back clean.

llvm-svn: 272126

2 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ddb85db34b6..af96316e4b1 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -4764,7 +4764,7 @@ static bool getTargetShuffleMaskIndices(SDValue MaskNode,
     if (VT.getScalarSizeInBits() != MaskEltSizeInBits)
       return false;
     if (auto *CN = dyn_cast<ConstantSDNode>(MaskNode.getOperand(0))) {
-      APInt MaskElement = CN->getAPIntValue();
+      const APInt &MaskElement = CN->getAPIntValue();
       for (unsigned i = 0, e = VT.getVectorNumElements(); i != e; ++i) {
         APInt RawElt = MaskElement.getLoBits(MaskEltSizeInBits);
         RawMask.push_back(RawElt.getZExtValue());
@@ -26928,7 +26928,7 @@ static SDValue combineShiftLeft(SDNode *N, SelectionDAG &DAG) {
       N0.getOperand(1).getOpcode() == ISD::Constant) {
     SDValue N00 = N0.getOperand(0);
     APInt Mask = cast<ConstantSDNode>(N0.getOperand(1))->getAPIntValue();
-    APInt ShAmt = N1C->getAPIntValue();
+    const APInt &ShAmt = N1C->getAPIntValue();
     Mask = Mask.shl(ShAmt);
     bool MaskOK = false;
     // We can handle cases concerning bit-widening nodes containing setcc_c if
@@ -27044,7 +27044,7 @@ static SDValue performShiftToAllZeros(SDNode *N, SelectionDAG &DAG,
   SDLoc DL(N);
   if (auto *AmtBV = dyn_cast<BuildVectorSDNode>(Amt))
     if (auto *AmtSplat = AmtBV->getConstantSplatNode()) {
-      APInt ShiftAmt = AmtSplat->getAPIntValue();
+      const APInt &ShiftAmt = AmtSplat->getAPIntValue();
       unsigned MaxAmount =
         VT.getSimpleVT().getVectorElementType().getSizeInBits();
 
@@ -30330,7 +30330,7 @@ static bool clobbersFlagRegisters(const SmallVector<StringRef, 4> &AsmPieces) {
 bool X86TargetLowering::ExpandInlineAsm(CallInst *CI) const {
   InlineAsm *IA = cast<InlineAsm>(CI->getCalledValue());
 
-  std::string AsmStr = IA->getAsmString();
+  const std::string &AsmStr = IA->getAsmString();
 
   IntegerType *Ty = dyn_cast<IntegerType>(CI->getType());
   if (!Ty || Ty->getBitWidth() % 16 != 0)
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 00debd849cd..86bae3e08db 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1543,7 +1543,7 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
               CS << CI->getZExtValue();
             } else {
               // print multi-word constant as (w0,w1)
-              auto Val = CI->getValue();
+              const auto &Val = CI->getValue();
               CS << "(";
               for (int i = 0, N = Val.getNumWords(); i < N; ++i) {
                 if (i > 0)