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This commit adds a new pass that can inject checks before indirect calls to make sure that these calls target known locations. It supports three types of checks and, at compile time, it can take the name of a custom function to call when an indirect call check fails. The default failure function ignores the error and continues. This pass incidentally moves the function JumpInstrTables::transformType from private to public and makes it static (with a new argument that specifies the table type to use); this is so that the CFI code can transform function types at call sites to determine which jump-instruction table to use for the check at that site. Also, this removes support for jumptables in ARM, pending further performance analysis and discussion. Review: http://reviews.llvm.org/D4167 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221708 91177308-0d34-0410-b5e6-96231b3b80d8
Analysis Opportunities:
//===---------------------------------------------------------------------===//
In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:
{1,+,3,+,2}<loop>
Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as
(-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))
In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.
//===---------------------------------------------------------------------===//
In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,
ScalarEvolution is forming this expression:
((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))
This could be folded to
(-1 * (trunc i64 undef to i32))
//===---------------------------------------------------------------------===//