http://llvm.org/bugs/show_bug.cgi?id=16380
Bug ID: 16380
Summary: Missed optimization opportunities for pointer
comparisons
Product: clang
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Given "p" as an object of type pointer-to-T and "x" as a complete object of
type T, the C++ standard defines the following expressions must either yield
"false" or an unspecified result:
p < nullptr
nullptr < p
p < &x
&x+1 < p
Thus, the compiler is free to constant fold these expressions to just "false",
and should do so. Similarly, if "a < b" folds to "false" by matching a pattern
above, "b > a" should also fold to "false", and "a >= b" and "b <= a" should
fold to "true".
Currently, Clang only constant folds the first pattern.
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