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Floating point intrinsics in LLVM are generally not speculatively executed, since most of them are defined to behave the same as libm functions, which set errno. However, the only error that can happen when executing ceil, floor, nearbyint, rint and round libm functions per POSIX.1-2001 is -ERANGE, and that requires the maximum value of the exponent to be smaller than the number of mantissa bits, which is not the case with any of the floating point types supported by LLVM. The trunc and copysign functions never set errno per per POSIX.1-2001. Differential Revision: http://reviews.llvm.org/D18643 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265262 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))
//===---------------------------------------------------------------------===//