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c3dd7f4b12
This patch adds the ability to peel off iterations of the first loop in loop
fusion. This can allow for both loops to have the same trip count, making it
legal for them to be fused together.
Here is a simple scenario peeling can be used in loop fusion:
for (i = 0; i < 10; ++i)
a[i] = a[i] + 3;
for (j = 1; j < 10; ++j)
b[j] = b[j] + 5;
Here is we can make use of peeling, and then fuse the two loops together. We
can peel off the 0th iteration of the loop i, and then combine loop i and j for
i = 1 to 10.
a[0] = a[0] +3;
for (i = 1; i < 10; ++i) {
a[i] = a[i] + 3;
b[i] = b[i] + 5;
}
Currently peeling with loop fusion is only supported for loops with constant
trip counts and a single exit point. Both unguarded and guarded loops are
supported.
Reviewed By: bmahjour (Bardia Mahjour), MaskRay (Fangrui Song)
Differential Revision: https://reviews.llvm.org/D82927
85 lines
3.2 KiB
LLVM
85 lines
3.2 KiB
LLVM
; RUN: opt -S -loop-fusion -loop-fusion-peel-max-count=3 < %s | FileCheck %s
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; Tests if we are able to fuse two guarded loops which have constant but
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; different trip counts. The first two iterations of the first loop should be
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; peeled off, and then the loops should be fused together.
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@B = common global [1024 x i32] zeroinitializer, align 16
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; CHECK-LABEL: void @main(i32* noalias %A)
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; CHECK-NEXT: entry:
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; CHECK: br i1 %cmp4, label %for.first.entry, label %for.end
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; CHECK: for.first.entry
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; CHECK-NEXT: br label %for.first.peel.begin
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; CHECK: for.first.peel.begin:
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; CHECK-NEXT: br label %for.first.peel
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; CHECK: for.first.peel:
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; CHECK: br label %for.first.peel.next
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; CHECK: for.first.peel.next:
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; CHECK-NEXT: br label %for.first.peel2
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; CHECK: for.first.peel2:
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; CHECK: br label %for.first.peel.next1
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; CHECK: for.first.peel.next1:
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; CHECK-NEXT: br label %for.first.peel.next11
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; CHECK: for.first.peel.next11:
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; CHECK-NEXT: br label %for.first.entry.peel.newph
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; CHECK: for.first.entry.peel.newph:
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; CHECK: br label %for.first
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; CHECK: for.first:
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; CHECK: br i1 %cmp3, label %for.first, label %for.second.exit
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; CHECK: for.second.exit:
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; CHECK: br label %for.end
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; CHECK: for.end:
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; CHECK-NEXT: ret void
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define void @main(i32* noalias %A) {
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entry:
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%cmp4 = icmp slt i64 0, 45
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br i1 %cmp4, label %for.first.entry, label %for.second.guard
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for.first.entry: ; preds = %entry
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br label %for.first
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for.first: ; preds = %for.first.entry, %for.first
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%i.05 = phi i64 [ %inc, %for.first ], [ 0, %for.first.entry ]
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%sub = sub nsw i64 %i.05, 3
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%add = add nsw i64 %i.05, 3
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%mul = mul nsw i64 %sub, %add
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%rem = srem i64 %mul, %i.05
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%conv = trunc i64 %rem to i32
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%arrayidx = getelementptr inbounds i32, i32* %A, i64 %i.05
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store i32 %conv, i32* %arrayidx, align 4
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%inc = add nsw i64 %i.05, 1
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%cmp = icmp slt i64 %inc, 45
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br i1 %cmp, label %for.first, label %for.first.exit
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for.first.exit: ; preds = %for.first
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br label %for.second.guard
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for.second.guard: ; preds = %for.first.exit, %entry
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%cmp31 = icmp slt i64 2, 45
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br i1 %cmp31, label %for.second.entry, label %for.end
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for.second.entry: ; preds = %for.second.guard
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br label %for.second
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for.second: ; preds = %for.second.entry, %for.second
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%i1.02 = phi i64 [ %inc14, %for.second ], [ 2, %for.second.entry ]
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%sub7 = sub nsw i64 %i1.02, 3
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%add8 = add nsw i64 %i1.02, 3
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%mul9 = mul nsw i64 %sub7, %add8
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%rem10 = srem i64 %mul9, %i1.02
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%conv11 = trunc i64 %rem10 to i32
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%arrayidx12 = getelementptr inbounds [1024 x i32], [1024 x i32]* @B, i64 0, i64 %i1.02
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store i32 %conv11, i32* %arrayidx12, align 4
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%inc14 = add nsw i64 %i1.02, 1
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%cmp3 = icmp slt i64 %inc14, 45
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br i1 %cmp3, label %for.second, label %for.second.exit
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for.second.exit: ; preds = %for.second
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br label %for.end
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for.end: ; preds = %for.second.exit, %for.second.guard
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ret void
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}
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