[clang] [Clang] Add missing __ob_trap check for sign change (PR #188340)

[Justin Stitt via cfe-commits]

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@@ -1663,6 +1667,20 @@ Value *ScalarExprEmitter::EmitScalarConversion(Value *Src, QualType SrcType,
 
   llvm::Type *DstTy = ConvertType(DstType);
 
+  // Determine whether an overflow behavior of 'trap' has been specified for
+  // either the destination or the source types. If so, we can elide sanitizer
+  // capability checks as this overflow behavior kind is also capable of
+  // emitting traps without runtime sanitizer support.
+  // Also skip instrumentation if either source or destination has 'wrap'
+  // behavior - the user has explicitly indicated they accept wrapping
+  // semantics. Use non-canonical types to preserve OBT annotations.
+  const auto *DstOBT = NoncanonicalDstType->getAs<OverflowBehaviorType>();
+  const auto *SrcOBT = NoncanonicalSrcType->getAs<OverflowBehaviorType>();
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JustinStitt wrote:

I decided to use these types

```c
  QualType NoncanonicalSrcType = SrcType;
  QualType NoncanonicalDstType = DstType;
```

as `SrcType` and `DstType` undergo various assignments and potential transformations in the function prologue I decided to use the types that I knew were OBTs.

Anyways, I'm sure using `SrcType` and `DstType` would have been fine but during development I debug-printed `Noncanonical...` and they had the right shape :)

https://github.com/llvm/llvm-project/pull/188340