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3da1a46d30
The fix for PR28705 will be committed consecutively.
In D12090, the ExprValueMap was added to reuse existing value during SCEV expansion.
However, const folding and sext/zext distribution can make the reuse still difficult.
A simplified case is: suppose we know S1 expands to V1 in ExprValueMap, and
S1 = S2 + C_a
S3 = S2 + C_b
where C_a and C_b are different SCEVConstants. Then we'd like to expand S3 as
V1 - C_a + C_b instead of expanding S2 literally. It is helpful when S2 is a
complex SCEV expr and S2 has no entry in ExprValueMap, which is usually caused
by the fact that S3 is generated from S1 after const folding.
In order to do that, we represent ExprValueMap as a mapping from SCEV to
ValueOffsetPair. We will save both S1->{V1, 0} and S2->{V1, C_a} into the
ExprValueMap when we create SCEV for V1. When S3 is expanded, it will first
expand S2 to V1 - C_a because of S2->{V1, C_a} in the map, then expand S3 to
V1 - C_a + C_b.
Differential Revision: https://reviews.llvm.org/D21313
llvm-svn: 278160
45 lines
1.8 KiB
LLVM
45 lines
1.8 KiB
LLVM
; RUN: opt < %s -loop-vectorize -force-vector-interleave=1 -force-vector-width=4 -S |FileCheck %s
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; SCEV expansion uses existing value or value + offset to reduce duplicate code expansion so foo should only generate one select inst after loop vectorization.
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; CHECK-LABEL: @foo(
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; CHECK: select
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; CHECK-NOT: select
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@ySrcL = common global i8* null, align 8
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@smL = common global i32 0, align 4
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define void @foo(i32 %rwL, i32 %kL, i32 %xfL) {
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entry:
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%sub = add nsw i32 %rwL, -1
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%shr = ashr i32 %xfL, 6
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%cmp.i = icmp slt i32 %sub, %shr
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%cond.i = select i1 %cmp.i, i32 %sub, i32 %shr
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%cmp6 = icmp sgt i32 %cond.i, %kL
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br i1 %cmp6, label %for.body.lr.ph, label %for.end
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for.body.lr.ph: ; preds = %entry
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%tmp = load i8*, i8** @ySrcL, align 8
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%tmp1 = sext i32 %kL to i64
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%tmp2 = sext i32 %cond.i to i64
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br label %for.body
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for.body: ; preds = %for.body, %for.body.lr.ph
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%indvars.iv = phi i64 [ %tmp1, %for.body.lr.ph ], [ %indvars.iv.next, %for.body ]
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%reduct.07 = phi i32 [ 0, %for.body.lr.ph ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds i8, i8* %tmp, i64 %indvars.iv
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%tmp3 = load i8, i8* %arrayidx, align 1
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%conv = zext i8 %tmp3 to i32
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%add = add nsw i32 %conv, %reduct.07
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%indvars.iv.next = add nsw i64 %indvars.iv, 1
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%cmp = icmp slt i64 %indvars.iv.next, %tmp2
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br i1 %cmp, label %for.body, label %for.end.loopexit
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for.end.loopexit: ; preds = %for.body
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%add.lcssa = phi i32 [ %add, %for.body ]
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br label %for.end
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for.end: ; preds = %for.end.loopexit, %entry
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%reduct.0.lcssa = phi i32 [ 0, %entry ], [ %add.lcssa, %for.end.loopexit ]
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store i32 %reduct.0.lcssa, i32* @smL, align 4
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ret void
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}
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