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Diffstat (limited to 'tools/js-optimizer.js')
| -rw-r--r-- | tools/js-optimizer.js | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js index 7d72b7b8..e61317af 100644 --- a/tools/js-optimizer.js +++ b/tools/js-optimizer.js @@ -801,7 +801,10 @@ function simplifyExpressions(ast) { // HEAP[x >> 2] // very often. We can in some cases do the shift on the variable itself when it is set, // to greatly reduce the number of shift operations. -// TODO: when shifting a variable, if there are other uses, keep an unshifted version too, to prevent slowdowns? +// XXX this optimization is deprecated and currently invalid: does not handle overflows +// or non-aligned (round numbers, x >> 2 is a multiple of 4). Both are ok to assume +// for pointers (undefined behavior otherwise), but invalid in general, and we do +// no sufficiently-well distinguish the cases. function optimizeShiftsInternal(ast, conservative) { var MAX_SHIFTS = 3; traverseGeneratedFunctions(ast, function(fun) { |