[LLVMdev] Rounding Mode for fptrunc Instruction
dalej at apple.com
Tue Mar 11 14:49:52 PDT 2008
On Mar 11, 2008, at 2:25 PM, Jon Sargeant wrote:
> What is the rounding mode for the fptrunc instruction? Round to zero?
> Round to nearest? Or undefined?
Rounding mode handling is currently primitive. FPTRUNC is (de facto)
round to nearest, as is the corresponding BE node FP_ROUND.
FP_ROUND_IN_REG is round to nearest on X86 and round to zero on
PowerPC. Better would be to have the rounding mode attached to the
nodes (or multiple nodes), but nobody's done it yet. We are a long
ways from having FENV_ACCESS work.
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