[IR] Add nowrap flags for trunc instruction (#85592)

This patch adds the nuw (no unsigned wrap) and nsw (no signed wrap)
poison-generating flags to the trunc instruction.

Discourse thread:
https://discourse.llvm.org/t/rfc-add-nowrap-flags-to-trunc/77453

1 files changed, 13 insertions, 3 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 6ee93f1..aa6c9c9 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5022,9 +5022,19 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
           return error("Invalid cast");
         I = CastInst::Create(CastOp, Op, ResTy);
       }
-      if (OpNum < Record.size() && isa<PossiblyNonNegInst>(I) &&
-          (Record[OpNum] & (1 << bitc::PNNI_NON_NEG)))
-        I->setNonNeg(true);
+
+      if (OpNum < Record.size()) {
+        if (Opc == Instruction::ZExt) {
+          if (Record[OpNum] & (1 << bitc::PNNI_NON_NEG))
+            cast<PossiblyNonNegInst>(I)->setNonNeg(true);
+        } else if (Opc == Instruction::Trunc) {
+          if (Record[OpNum] & (1 << bitc::TIO_NO_UNSIGNED_WRAP))
+            cast<TruncInst>(I)->setHasNoUnsignedWrap(true);
+          if (Record[OpNum] & (1 << bitc::TIO_NO_SIGNED_WRAP))
+            cast<TruncInst>(I)->setHasNoSignedWrap(true);
+        }
+      }
+
       InstructionList.push_back(I);
       break;
     }