[clang][UBSan] Sanitization for alignment assumptions.
Summary:
UB isn't nice. It's cool and powerful, but not nice.
Having a way to detect it is nice though.
[[ https://wg21.link/p1007r3 | P1007R3: std::assume_aligned ]] / http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1007r2.pdf says:
```
We propose to add this functionality via a library function instead of a core language attribute.
...
If the pointer passed in is not aligned to at least N bytes, calling assume_aligned results in undefined behaviour.
```
This differential teaches clang to sanitize all the various variants of this assume-aligned attribute.
Requires D54588 for LLVM IRBuilder changes.
The compiler-rt part is D54590.
This is a second commit, the original one was r351105,
which was mass-reverted in r351159 because 2 compiler-rt tests were failing.
Reviewers: ABataev, craig.topper, vsk, rsmith, rnk, #sanitizers, erichkeane, filcab, rjmccall
Reviewed By: rjmccall
Subscribers: chandlerc, ldionne, EricWF, mclow.lists, cfe-commits, bkramer
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D54589
llvm-svn: 351177
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index f53bb33..1c14d4c 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -258,8 +258,11 @@
AVAttr = TTy->getDecl()->getAttr<AlignValueAttr>();
} else {
// Assumptions for function parameters are emitted at the start of the
- // function, so there is no need to repeat that here.
- if (isa<ParmVarDecl>(VD))
+ // function, so there is no need to repeat that here,
+ // unless the alignment-assumption sanitizer is enabled,
+ // then we prefer the assumption over alignment attribute
+ // on IR function param.
+ if (isa<ParmVarDecl>(VD) && !CGF.SanOpts.has(SanitizerKind::Alignment))
return;
AVAttr = VD->getAttr<AlignValueAttr>();
@@ -276,7 +279,8 @@
Value *AlignmentValue = CGF.EmitScalarExpr(AVAttr->getAlignment());
llvm::ConstantInt *AlignmentCI = cast<llvm::ConstantInt>(AlignmentValue);
- CGF.EmitAlignmentAssumption(V, AlignmentCI->getZExtValue());
+ CGF.EmitAlignmentAssumption(V, E, AVAttr->getLocation(),
+ AlignmentCI->getZExtValue());
}
/// EmitLoadOfLValue - Given an expression with complex type that represents a