[PATCH] D88937: [KnownBits] Add a sextOrTrunc method

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet created this revision.
qcolombet added reviewers: fhahn, nikic, aqjune, spatel, RKSimon, efriedma, lebedev.ri.
Herald added a project: LLVM.
qcolombet requested review of this revision.

We already offer zextOrTrunc and it seems natural to offer the
same capability for sign extension.

This patch is a preparatory addition useful for future computeKnownBits
developments.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D88937

Files:
  llvm/include/llvm/Support/KnownBits.h


Index: llvm/include/llvm/Support/KnownBits.h
===================================================================
--- llvm/include/llvm/Support/KnownBits.h
+++ llvm/include/llvm/Support/KnownBits.h
@@ -166,6 +166,16 @@
     return *this;
   }
 
+  /// Return known bits for a sign extension or truncation of the value we're
+  /// tracking.
+  KnownBits sextOrTrunc(unsigned BitWidth) const {
+    if (BitWidth > getBitWidth())
+      return sext(BitWidth);
+    if (BitWidth < getBitWidth())
+      return trunc(BitWidth);
+    return *this;
+  }
+
   /// Return a KnownBits with the extracted bits
   /// [bitPosition,bitPosition+numBits).
   KnownBits extractBits(unsigned NumBits, unsigned BitPosition) const {


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