diff options
| -rw-r--r-- | lib/Target/README.txt | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index e000a9d396..4032c333f7 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -2247,10 +2247,15 @@ entry: ret double %mul } -We should be able to fold away this fmul to a constant, there is no 32-bit -integer which after sitofp will generate a NaN, inf, or -0.0. We should fold -this whenever the floating point type has enough exponent bits to represent -the largest integer value as < inf. +We should be able to fold away this fmul to 0.0. More generally, fmul(x,0.0) +can be folded to 0.0 if we can prove that the LHS is not -0.0, not a NaN, and +not an INF. The CannotBeNegativeZero predicate in value tracking should be +extended to support general "fpclassify" operations that can return +yes/no/unknown for each of these predicates. + +In this predicate, we know that [us]itofp is trivially never NaN or -0.0, and +we know that it isn't +/-Inf if the floating point type has enough exponent bits +to represent the largest integer value as < inf. //===---------------------------------------------------------------------===// |