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[LV] Model if-converted phi node costs

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Phi nodes in non-header blocks are converted to select instructions after
if-conversion. This patch updates the cost model to account for the selects.

Differential Revision: https://reviews.llvm.org/D31906

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300980 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthew Simpson 2017-04-21 14:14:54 +00:00
parent 9eb6db17b6
commit 915a4bc0f9
2 changed files with 96 additions and 2 deletions
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12
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -7324,8 +7324,16 @@ unsigned LoopVectorizationCostModel::getInstructionCost(Instruction *I,
return TTI.getShuffleCost(TargetTransformInfo::SK_ExtractSubvector,
VectorTy, VF - 1, VectorTy);
// TODO: IF-converted IFs become selects.
return 0;
// Phi nodes in non-header blocks (not inductions, reductions, etc.) are
// converted into select instructions. We require N - 1 selects per phi
// node, where N is the number of incoming values.
if (VF > 1 && Phi->getParent() != TheLoop->getHeader())
return (Phi->getNumIncomingValues() - 1) *
TTI.getCmpSelInstrCost(
Instruction::Select, ToVectorTy(Phi->getType(), VF),
ToVectorTy(Type::getInt1Ty(Phi->getContext()), VF));
return TTI.getCFInstrCost(Instruction::PHI);
}
case Instruction::UDiv:
case Instruction::SDiv:

86
test/Transforms/LoopVectorize/phi-cost.ll Normal file
View File

@ -0,0 +1,86 @@
; REQUIRES: asserts
; RUN: opt < %s -loop-vectorize -force-vector-width=2 -force-vector-interleave=1 -instcombine -debug-only=loop-vectorize -disable-output -print-after=instcombine 2>&1 | FileCheck %s
target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
; CHECK-LABEL: phi_two_incoming_values
; CHECK: LV: Found an estimated cost of 1 for VF 2 For instruction: %i = phi i64 [ %i.next, %if.end ], [ 0, %entry ]
; CHECK: LV: Found an estimated cost of 1 for VF 2 For instruction: %tmp5 = phi i32 [ %tmp1, %for.body ], [ %tmp4, %if.then ]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %vector.body ]
; CHECK: [[WIDE_LOAD:%.*]] = load <2 x i32>, <2 x i32>* {{.*}}
; CHECK: [[TMP5:%.*]] = icmp sgt <2 x i32> [[WIDE_LOAD]], zeroinitializer
; CHECK-NEXT: [[TMP6:%.*]] = add <2 x i32> [[WIDE_LOAD]], <i32 1, i32 1>
; CHECK-NEXT: [[PREDPHI:%.*]] = select <2 x i1> [[TMP5]], <2 x i32> [[TMP6]], <2 x i32> [[WIDE_LOAD]]
; CHECK: store <2 x i32> [[PREDPHI]], <2 x i32>* {{.*}}
; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[INDEX]], 2
;
define void @phi_two_incoming_values(i32* %a, i32* %b, i64 %n) {
entry:
br label %for.body
for.body:
%i = phi i64 [ %i.next, %if.end ], [ 0, %entry ]
%tmp0 = getelementptr inbounds i32, i32* %a, i64 %i
%tmp1 = load i32, i32* %tmp0, align 4
%tmp2 = getelementptr inbounds i32, i32* %b, i64 %i
%tmp3 = icmp sgt i32 %tmp1, 0
br i1 %tmp3, label %if.then, label %if.end
if.then:
%tmp4 = add i32 %tmp1, 1
br label %if.end
if.end:
%tmp5 = phi i32 [ %tmp1, %for.body ], [ %tmp4, %if.then ]
store i32 %tmp5, i32* %tmp2, align 4
%i.next = add i64 %i, 1
%cond = icmp eq i64 %i, %n
br i1 %cond, label %for.end, label %for.body
for.end:
ret void
}
; CHECK-LABEL: phi_three_incoming_values
; CHECK: LV: Found an estimated cost of 1 for VF 2 For instruction: %i = phi i64 [ %i.next, %if.end ], [ 0, %entry ]
; CHECK: LV: Found an estimated cost of 2 for VF 2 For instruction: %tmp8 = phi i32 [ 9, %for.body ], [ 3, %if.then ], [ %tmp7, %if.else ]
; CHECK: vector.body:
; CHECK-NEXT: [[INDEX:%.*]] = phi i64 [ 0, %vector.ph ], [ [[INDEX_NEXT:%.*]], %vector.body ]
; CHECK: [[PREDPHI:%.*]] = select <2 x i1> {{.*}}, <2 x i32> <i32 3, i32 3>, <2 x i32> <i32 9, i32 9>
; CHECK: [[PREDPHI7:%.*]] = select <2 x i1> {{.*}}, <2 x i32> {{.*}}, <2 x i32> [[PREDPHI]]
; CHECK: store <2 x i32> [[PREDPHI7]], <2 x i32>* {{.*}}
; CHECK-NEXT: [[INDEX_NEXT]] = add i64 [[INDEX]], 2
;
define void @phi_three_incoming_values(i32* %a, i32* %b, i64 %n) {
entry:
br label %for.body
for.body:
%i = phi i64 [ %i.next, %if.end ], [ 0, %entry ]
%tmp0 = getelementptr inbounds i32, i32* %a, i64 %i
%tmp1 = load i32, i32* %tmp0, align 4
%tmp2 = getelementptr inbounds i32, i32* %b, i64 %i
%tmp3 = load i32, i32* %tmp2, align 4
%tmp4 = icmp sgt i32 %tmp1, %tmp3
br i1 %tmp4, label %if.then, label %if.end
if.then:
%tmp5 = icmp sgt i32 %tmp1, 19
br i1 %tmp5, label %if.end, label %if.else
if.else:
%tmp6 = icmp slt i32 %tmp3, 4
%tmp7 = select i1 %tmp6, i32 4, i32 5
br label %if.end
if.end:
%tmp8 = phi i32 [ 9, %for.body ], [ 3, %if.then ], [ %tmp7, %if.else ]
store i32 %tmp8, i32* %tmp0, align 4
%i.next = add i64 %i, 1
%cond = icmp eq i64 %i, %n
br i1 %cond, label %for.end, label %for.body
for.end:
ret void
}