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[LoopVectorizer] Count dependencies of consecutive pointers as uniforms

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For the purpose of calculating the cost of the loop at various vectorization
factors, we need to count dependencies of consecutive pointers as uniforms
(which means that the VF = 1 cost is used for all overall VF values).

For example, the TSVC benchmark function s173 has:
  ...
  %3 = add nsw i64 %indvars.iv, 16000
  %arrayidx8 = getelementptr inbounds %struct.GlobalData* @global_data, i64 0, i32 0, i64 %3
  ...
and we must realize that the add will be a scalar in order to correctly deduce
it to be profitable to vectorize this on PowerPC with VSX enabled. In fact, all
dependencies of a consecutive pointer must be a scalar (uniform), and so we
simply need to add all consecutive pointers to the worklist that currently
detects collects uniforms.

Fixes PR19296.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205387 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2014-04-02 02:34:49 +00:00
parent d486d104b5
commit 081e6fcd17
3 changed files with 65 additions and 0 deletions
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10
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -3656,6 +3656,16 @@ void LoopVectorizationLegality::collectLoopUniforms() {
// Start with the conditional branch and walk up the block.
Worklist.push_back(Latch->getTerminator()->getOperand(0));
// Also add all consecutive pointer values; these values will be uniform
// after vectorization (and subsequent cleanup) and, until revectorization is
// supported, all dependencies must also be uniform.
for (Loop::block_iterator B = TheLoop->block_begin(),
BE = TheLoop->block_end(); B != BE; ++B)
for (BasicBlock::iterator I = (*B)->begin(), IE = (*B)->end();
I != IE; ++I)
if (I->getType()->isPointerTy() && isConsecutivePtr(I))
Worklist.insert(Worklist.end(), I->op_begin(), I->op_end());
while (Worklist.size()) {
Instruction *I = dyn_cast<Instruction>(Worklist.back());
Worklist.pop_back();

4
test/Transforms/LoopVectorize/PowerPC/lit.local.cfg Normal file
View File

@ -0,0 +1,4 @@
targets = set(config.root.targets_to_build.split())
if not 'PowerPC' in targets:
config.unsupported = True

51
test/Transforms/LoopVectorize/PowerPC/vsx-tsvc-s173.ll Normal file
View File

@ -0,0 +1,51 @@
; RUN: opt < %s -mcpu=pwr7 -mattr=+vsx -loop-vectorize -instcombine -S | FileCheck %s
target datalayout = "E-m:e-i64:64-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
%struct.GlobalData = type { [32000 x float], [3 x i32], [4 x i8], [32000 x float], [5 x i32], [12 x i8], [32000 x float], [7 x i32], [4 x i8], [32000 x float], [11 x i32], [4 x i8], [32000 x float], [13 x i32], [12 x i8], [256 x [256 x float]], [17 x i32], [12 x i8], [256 x [256 x float]], [19 x i32], [4 x i8], [256 x [256 x float]], [23 x i32], [4 x i8], [256 x [256 x float]] }
@global_data = external global %struct.GlobalData, align 16
@ntimes = external hidden unnamed_addr global i32, align 4
define signext i32 @s173() #0 {
entry:
%0 = load i32* @ntimes, align 4
%cmp21 = icmp sgt i32 %0, 0
br i1 %cmp21, label %for.cond1.preheader, label %for.end12
for.cond1.preheader: ; preds = %for.end, %entry
%nl.022 = phi i32 [ %inc11, %for.end ], [ 0, %entry ]
br label %for.body3
for.body3: ; preds = %for.body3, %for.cond1.preheader
%indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.body3 ]
%arrayidx = getelementptr inbounds %struct.GlobalData* @global_data, i64 0, i32 0, i64 %indvars.iv
%1 = load float* %arrayidx, align 4
%arrayidx5 = getelementptr inbounds %struct.GlobalData* @global_data, i64 0, i32 3, i64 %indvars.iv
%2 = load float* %arrayidx5, align 4
%add = fadd float %1, %2
%3 = add nsw i64 %indvars.iv, 16000
%arrayidx8 = getelementptr inbounds %struct.GlobalData* @global_data, i64 0, i32 0, i64 %3
store float %add, float* %arrayidx8, align 4
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 16000
br i1 %exitcond, label %for.end, label %for.body3
for.end: ; preds = %for.body3
%inc11 = add nsw i32 %nl.022, 1
%4 = load i32* @ntimes, align 4
%mul = mul nsw i32 %4, 10
%cmp = icmp slt i32 %inc11, %mul
br i1 %cmp, label %for.cond1.preheader, label %for.end12
for.end12: ; preds = %for.end, %entry
ret i32 0
; CHECK-LABEL: @s173
; CHECK: load <4 x float>*
; CHECK: add i64 %index, 16000
; CHECK: ret i32 0
}
attributes #0 = { nounwind }