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Rollup merge of #49122 - scottmcm:z-align-attr, r=cramertj

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Add a -Z flag for LLVM align attributes on arguments

LLVM seems to still put the assume calls in when inlining, so this probably isn't in a place where it can be turned on by default, but it's interesting to experiment with.

For example, this makes `mem::swap::<u64x8>` be 8x `vmovaps	ymm` instead of 16x `vmovups	xmm`, on my cpu.
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kennytm 2018-03-25 01:26:30 +08:00 committed by GitHub
commit c892e68387
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2 changed files with 3 additions and 1 deletions
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2
src/librustc/session/config.rs
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@ -1208,6 +1208,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"set the MIR optimization level (0-3, default: 1)"),
mutable_noalias: bool = (false, parse_bool, [UNTRACKED],
"emit noalias metadata for mutable references"),
arg_align_attributes: bool = (false, parse_bool, [UNTRACKED],
"emit align metadata for reference arguments"),
dump_mir: Option<String> = (None, parse_opt_string, [UNTRACKED],
"dump MIR state at various points in translation"),
dump_mir_dir: String = (String::from("mir_dump"), parse_string, [UNTRACKED],

2
src/librustc_trans/abi.rs
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@ -779,7 +779,7 @@ impl<'a, 'tcx> FnType<'tcx> {
// HACK(eddyb) LLVM inserts `llvm.assume` calls when inlining functions
// with align attributes, and those calls later block optimizations.
if !is_return {
if !is_return && !cx.tcx.sess.opts.debugging_opts.arg_align_attributes {
attrs.pointee_align = None;
}