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

[via llvm-commits]

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@@ -27,6 +27,10 @@ bool Operator::hasPoisonGeneratingFlags() const {
     auto *OBO = cast<OverflowingBinaryOperator>(this);
     return OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap();
   }
+  case Instruction::Trunc: {
+    auto *TI = dyn_cast<TruncInst>(this);
+    return TI->hasNoUnsignedWrap() || TI->hasNoSignedWrap();
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elhewaty wrote:

Can you think of a small test for this?
```
define i32 @unittest_data_add() {
entry:
  %add = add i32 trunc (i64 sub (i64 0, i64 ptrtoint (ptr @__dtbo_testcases_begin to i64)) to i32), 1
  %conv = sext i32 %add to i64
  %call1 = call ptr @kmalloc(i64 %conv, ptr null) ; I tried to replace this with call i32 @use(i64 %conv) and remove all the other functions, but It works fine
  ret i32 0
}
```

https://github.com/llvm/llvm-project/pull/85592