[APInt] Add APInt::insertBits() method to insert an APInt into a larger APInt

We currently have to insert bits via a temporary variable of the same size as the target with various shift/mask stages, resulting in further temporary variables, all of which require the allocation of memory for large APInts (MaskSizeInBits > 64).

This is another of the compile time issues identified in PR32037 (see also D30265).

This patch adds the APInt::insertBits() helper method which avoids the temporary memory allocation and masks/inserts the raw bits directly into the target.

Differential Revision: https://reviews.llvm.org/D30780

llvm-svn: 297458

1 files changed, 3 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 533ee7c6a43..872f3d5d12a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -5318,12 +5318,11 @@ static bool getTargetConstantBitsFromNode(SDValue Op, unsigned EltSizeInBits,
       return true;
     }
     if (auto *CInt = dyn_cast<ConstantInt>(Cst)) {
-      Mask |= CInt->getValue().zextOrTrunc(SizeInBits).shl(BitOffset);
+      Mask.insertBits(CInt->getValue(), BitOffset);
       return true;
     }
     if (auto *CFP = dyn_cast<ConstantFP>(Cst)) {
-      APInt CstBits = CFP->getValueAPF().bitcastToAPInt();
-      Mask |= CstBits.zextOrTrunc(SizeInBits).shl(BitOffset);
+      Mask.insertBits(CFP->getValueAPF().bitcastToAPInt(), BitOffset);
       return true;
     }
     return false;
@@ -5340,7 +5339,7 @@ static bool getTargetConstantBitsFromNode(SDValue Op, unsigned EltSizeInBits,
       }
       auto *Cst = cast<ConstantSDNode>(Src);
       APInt Bits = Cst->getAPIntValue().zextOrTrunc(SrcEltSizeInBits);
-      MaskBits |= Bits.zext(SizeInBits).shl(BitOffset);
+      MaskBits.insertBits(Bits, BitOffset);
     }
     return SplitBitData();
   }