Author: kparzysz
Date: Fri May 19 07:03:34 2017
New Revision: 303419
URL: http://llvm.org/viewvc/llvm-project?rev=303419&view=rev
Log:
Restore and update documentation comment for EmitPointerWithAlignment
Modified:
cfe/trunk/lib/CodeGen/CodeGenFunction.h
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=303419&r1=303418&r2=303419&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Fri May 19 07:03:34 2017
@@ -3746,12 +3746,23 @@ public:
unsigned ParamsToSkip = 0,
EvaluationOrder Order = EvaluationOrder::Default);
- /// EmitPointerWithAlignment - Given an expression with a pointer
- /// type, emit the value and compute our best estimate of the
- /// alignment of the pointee.
+ /// EmitPointerWithAlignment - Given an expression with a pointer type,
+ /// emit the value and compute our best estimate of the alignment of the
+ /// pointee.
///
- /// Note that this function will conservatively fall back on the type
- /// when it doesn't
+ /// \param BaseInfo - If non-null, this will be initialized with
+ /// information about the source of the alignment and the may-alias
+ /// attribute. Note that this function will conservatively fall back on
+ /// the type when it doesn't recognize the expression and may-alias will
+ /// be set to false.
+ ///
+ /// One reasonable way to use this information is when there's a language
+ /// guarantee that the pointer must be aligned to some stricter value, and
+ /// we're simply trying to ensure that sufficiently obvious uses of under-
+ /// aligned objects don't get miscompiled; for example, a placement new
+ /// into the address of a local variable. In such a case, it's quite
+ /// reasonable to just ignore the returned alignment when it isn't from an
+ /// explicit source.
Address EmitPointerWithAlignment(const Expr *Addr,
LValueBaseInfo *BaseInfo = nullptr);
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