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iLoopVectorize: Non commutative operators can be used as reduction variables as long as the reduction chain is used in the LHS.

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PR14803.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171583 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2013-01-05 01:15:47 +00:00
parent f7737b5baa
commit d5b92c3891
3 changed files with 44 additions and 7 deletions
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17
lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@ -1912,10 +1912,6 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
if (Iter->use_empty())
return false;
// Any reduction instr must be of one of the allowed kinds.
if (!isReductionInstr(Iter, Kind))
return false;
// Did we find a user inside this loop already ?
bool FoundInBlockUser = false;
// Did we reach the initial PHI node already ?
@ -1953,6 +1949,16 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi,
if (FoundInBlockUser)
return false;
FoundInBlockUser = true;
// Any reduction instr must be of one of the allowed kinds.
if (!isReductionInstr(U, Kind))
return false;
// Reductions of instructions such as Div, and Sub is only
// possible if the LHS is the reduction variable.
if (!U->isCommutative() && U->getOperand(0) != Iter)
return false;
Iter = U;
}
@ -1985,8 +1991,11 @@ LoopVectorizationLegality::isReductionInstr(Instruction *I,
case Instruction::PHI:
// possibly.
return true;
case Instruction::Sub:
case Instruction::Add:
return Kind == IntegerAdd;
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::Mul:
return Kind == IntegerMult;
case Instruction::And:

2
test/Transforms/LoopVectorize/gcc-examples.ll
View File

@ -241,7 +241,7 @@ define void @example8(i32 %x) nounwind uwtable ssp {
}
;CHECK: @example9
;CHECK-NOT: phi <4 x i32>
;CHECK: phi <4 x i32>
;CHECK: ret i32
define i32 @example9() nounwind uwtable readonly ssp {
br label %1

32
test/Transforms/LoopVectorize/reduction.ll
View File

@ -296,11 +296,12 @@ for.end: ; preds = %for.body, %entry
ret i32 %x.0.lcssa
}
;CHECK: @reduction_sub_lhs
; In this code the subtracted variable is on the RHS and this is not an induction variable.
;CHECK: @reduction_sub_rhs
;CHECK-NOT: phi <4 x i32>
;CHECK-NOT: sub nsw <4 x i32>
;CHECK: ret i32
define i32 @reduction_sub_lhs(i32 %n, i32* noalias nocapture %A) nounwind uwtable readonly {
define i32 @reduction_sub_rhs(i32 %n, i32* noalias nocapture %A) nounwind uwtable readonly {
entry:
%cmp4 = icmp sgt i32 %n, 0
br i1 %cmp4, label %for.body, label %for.end
@ -320,3 +321,30 @@ for.end: ; preds = %for.body, %entry
%x.0.lcssa = phi i32 [ 0, %entry ], [ %sub, %for.body ]
ret i32 %x.0.lcssa
}
; In this test the reduction variable is on the LHS and we can vectorize it.
;CHECK: @reduction_sub_lhs
;CHECK: phi <4 x i32>
;CHECK: sub nsw <4 x i32>
;CHECK: ret i32
define i32 @reduction_sub_lhs(i32 %n, i32* noalias nocapture %A) nounwind uwtable readonly {
entry:
%cmp4 = icmp sgt i32 %n, 0
br i1 %cmp4, label %for.body, label %for.end
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
%x.05 = phi i32 [ %sub, %for.body ], [ 0, %entry ]
%arrayidx = getelementptr inbounds i32* %A, i64 %indvars.iv
%0 = load i32* %arrayidx, align 4
%sub = sub nsw i32 %x.05, %0
%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 %for.end, label %for.body
for.end: ; preds = %for.body, %entry
%x.0.lcssa = phi i32 [ 0, %entry ], [ %sub, %for.body ]
ret i32 %x.0.lcssa
}