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LoopVectorize: Add support for write-only loops when the write destination is a single pointer.

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Speedup SciMark by 1%

llvm-svn: 167035
This commit is contained in:
Nadav Rotem 2012-10-30 18:36:45 +00:00
parent 74fd05ff3f
commit 69e6bca813
2 changed files with 33 additions and 0 deletions
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7
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -1348,6 +1348,13 @@ bool LoopVectorizationLegality::canVectorizeMemory(BasicBlock &BB) {
Reads.push_back(Ptr);
}
// If we write (or read-write) to a single destination and there are no
// other reads in this loop then is it safe to vectorize.
if (ReadWrites.size() == 1 && Reads.size() == 0) {
DEBUG(dbgs() << "LV: Found a write-only loop!\n");
return true;
}
// Now that the pointers are in two lists (Reads and ReadWrites), we
// can check that there are no conflicts between each of the writes and
// between the writes to the reads.

26
test/Transforms/LoopVectorize/write-only.ll Normal file
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@ -0,0 +1,26 @@
; RUN: opt < %s -loop-vectorize -force-vector-width=4 -dce -instcombine -licm -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.8.0"
;CHECK: @read_mod_write_single_ptr
;CHECK: load <4 x float>
;CHECK: ret i32
define i32 @read_mod_write_single_ptr(float* nocapture %a, i32 %n) nounwind uwtable ssp {
%1 = icmp sgt i32 %n, 0
br i1 %1, label %.lr.ph, label %._crit_edge
.lr.ph: ; preds = %0, %.lr.ph
%indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ 0, %0 ]
%2 = getelementptr inbounds float* %a, i64 %indvars.iv
%3 = load float* %2, align 4
%4 = fmul float %3, 3.000000e+00
store float %4, float* %2, align 4
%indvars.iv.next = add i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp eq i32 %lftr.wideiv, %n
br i1 %exitcond, label %._crit_edge, label %.lr.ph
._crit_edge: ; preds = %.lr.ph, %0
ret i32 undef
}