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Diffstat (limited to 'docs/LangRef.html')
| -rw-r--r-- | docs/LangRef.html | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/docs/LangRef.html b/docs/LangRef.html index 1f9f80d6d4..adc5d9a143 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -2091,6 +2091,7 @@ Classifications</a> </div> instruction</a>.</dd> <dt><b><tt>getelementptr ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt> + <dt><b><tt>getelementptr inbounds ( CSTPTR, IDX0, IDX1, ... )</tt></b></dt> <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on constants. As with the <a href="#i_getelementptr">getelementptr</a> instruction, the index list may have zero or more indexes, which are @@ -3902,6 +3903,7 @@ Instruction</a> </div> <h5>Syntax:</h5> <pre> <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}* + <result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}* </pre> <h5>Overview:</h5> @@ -3990,6 +3992,20 @@ entry: } </pre> +<p>If the <tt>inbounds</tt> keyword is present, the result value of the + <tt>getelementptr</tt> is undefined if the base pointer is not pointing + into an allocated object, or if any of the addresses formed by successive + addition of the offsets implied by the indices to the base address is + outside of the allocated object into which the base pointer points.</p> + +<p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to + the base address with silently-wrapping two's complement arithmetic, and + the result value of the <tt>getelementptr</tt> may be outside the object + pointed to by the base pointer. The result value may not necessarily be + used to access memory though, even if it happens to point into allocated + storage. See the <a href="#pointeraliasing">Pointer Aliasing Rules</a> + section for more information.</p> + <p>The getelementptr instruction is often confusing. For some more insight into how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p> |