On Thu, Sep 3, 2015 at 8:15 AM, Oded Gabbay <oded.gab...@gmail.com> wrote:
> round(val*dscale) produces a double result, as val and dscale are double.
> However, LLVMConstInt receives unsigned long long, so there is an
> implicit conversion from double to unsigned long long.
> This is an undefined behavior. Therefore, we need to first explicitly
> convert the round result to long long, and then let the compiler handle
> conversion from that to unsigned long long.
>
> This bug manifests itself in POWER, where all IMM values of -1 are being
> converted to 0 implicitly, causing a wrong LLVM IR output.
>
> Signed-off-by: Oded Gabbay <oded.gab...@gmail.com>
> CC: "10.6" <mesa-sta...@lists.freedesktop.org>
> ---
> src/gallium/auxiliary/gallivm/lp_bld_const.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_const.c
> b/src/gallium/auxiliary/gallivm/lp_bld_const.c
> index 0f5a8f8..9cd7c55 100644
> --- a/src/gallium/auxiliary/gallivm/lp_bld_const.c
> +++ b/src/gallium/auxiliary/gallivm/lp_bld_const.c
> @@ -311,7 +311,7 @@ lp_build_const_elem(struct gallivm_state *gallivm,
> else {
> double dscale = lp_const_scale(type);
>
> - elem = LLVMConstInt(elem_type, round(val*dscale), 0);
> + elem = LLVMConstInt(elem_type, (long long) round(val*dscale), 0);
Looks like I'm late to the party, but shouldn't you just use llround()?
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