forked from OSchip/llvm-project
8a12cae862
This patch extends the available-value logic to detect loads
of pointer-selects that can be replaced by a value select.
For example, consider the code below:
loop:
%sel.phi = phi i32* [ %start, %ph ], [ %sel, %ph ]
%l = load %ptr
%l.sel = load %sel.phi
%sel = select cond, %ptr, %sel.phi
...
exit:
%res = load %sel
use(%res)
The load of the pointer phi can be replaced by a load of the start value
outside the loop and a new phi/select chain based on the loaded values,
as illustrated below
%l.start = load %start
loop:
sel.phi.prom = phi i32 [ %l.start, %ph ], [ %sel.prom, %ph ]
%l = load %ptr
%sel.prom = select cond, %l, %sel.phi.prom
...
exit:
use(%sel.prom)
This is a first step towards alllowing vectorizing loops using common libc++
library functions, like std::min_element (https://clang.godbolt.org/z/6czGzzqbs)
#include <vector>
#include <algorithm>
int foo(const std::vector<int> &V) {
return *std::min_element(V.begin(), V.end());
}
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D118143
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| .. | ||
| 2009-02-17-LoadPRECrash.ll | ||
| 2009-06-17-InvalidPRE.ll | ||
| 2011-06-01-NonLocalMemdepMiscompile.ll | ||
| 2017-06-28-pre-load-dbgloc.ll | ||
| 2017-10-16-LoadPRECrash.ll | ||
| 2018-06-08-pre-load-dbgloc-no-null-opt.ll | ||
| atomic.ll | ||
| invariant-load.ll | ||
| load-metadata.ll | ||
| load-pre-align.ll | ||
| load-pre-licm.ll | ||
| load-pre-metadata-accsess-group.ll | ||
| load-pre-nonlocal.ll | ||
| load-pre-split-backedge.ll | ||
| local-pre.ll | ||
| lpre-call-wrap-2.ll | ||
| lpre-call-wrap.ll | ||
| modified-status.ll | ||
| nonintegral.ll | ||
| phi-translate-2.ll | ||
| phi-translate.ll | ||
| pre-after-rle.ll | ||
| pre-aliasning-path.ll | ||
| pre-basic-add.ll | ||
| pre-gep-load.ll | ||
| pre-jt-add.ll | ||
| pre-load-guards.ll | ||
| pre-load-implicit-cf-updates.ll | ||
| pre-load-in-loop.ll | ||
| pre-load-through-select.ll | ||
| pre-load.ll | ||
| pre-loop-load-new-pm.ll | ||
| pre-loop-load-through-select.ll | ||
| pre-loop-load.ll | ||
| pre-no-cost-phi.ll | ||
| pre-poison-add.ll | ||
| pre-single-pred.ll | ||
| preserve-tbaa.ll | ||
| rle-addrspace-cast.ll | ||
| rle-phi-translate.ll | ||
| rle-semidominated.ll | ||
| rle.ll | ||
| volatile.ll | ||