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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
106 lines
4.0 KiB
LLVM
106 lines
4.0 KiB
LLVM
; RUN: opt -S -loop-fusion -loop-fusion-peel-max-count=3 < %s | FileCheck %s
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; Tests whether we can fuse two loops together if they have constant but a
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; different tripcount.
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; The first three iterations of the first loop should be peeled, and then the
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; two loops should be fused together in this example.
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; C Code
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;
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; int B[1024];
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;
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; void function(int *arg) {
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; for (int i = 0; i != 100; ++i)
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; arg[i] = ((i - 3)*(i+3)) % i;
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;
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; for (int i = 3; i != 100; ++i)
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; B[i] = ((i-6)*(i+3)) % i;
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; }
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; CHECK-LABEL: void @function(i32* noalias %arg)
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; CHECK-NEXT: for.first.preheader:
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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.latch.peel
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; CHECK: for.first.latch.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.latch.peel10
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; CHECK: for.first.latch.peel10:
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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.peel15
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; CHECK: for.first.peel15:
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; CHECK: br label %for.first.latch.peel23
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; CHECK: for.first.latch.peel23:
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; CHECK: br label %for.first.peel.next14
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; CHECK: for.first.peel.next14:
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; CHECK-NEXT: br label %for.first.peel.next27
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; CHECK: for.first.peel.next27:
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; CHECK-NEXT: br label %for.first.preheader.peel.newph
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; CHECK: for.first.preheader.peel.newph:
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; CHECK-NEXT: br label %for.first
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; CHECK: for.first:
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; CHECK: br label %for.first.latch
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; CHECK: for.first.latch:
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; CHECK: br label %for.second.latch
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; CHECK: for.second.latch:
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; CHECK: br i1 %exitcond, label %for.first, label %for.end
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; CHECK: for.end:
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; CHECK-NEXT: ret void
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@B = common global [1024 x i32] zeroinitializer, align 16
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define void @function(i32* noalias %arg) {
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for.first.preheader:
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br label %for.first
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for.first: ; preds = %for.first.preheader, %for.first.latch
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%.014 = phi i32 [ 0, %for.first.preheader ], [ %tmp15, %for.first.latch ]
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%indvars.iv23 = phi i64 [ 0, %for.first.preheader ], [ %indvars.iv.next3, %for.first.latch ]
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%tmp = add nsw i32 %.014, -3
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%tmp8 = add nuw nsw i64 %indvars.iv23, 3
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%tmp9 = trunc i64 %tmp8 to i32
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%tmp10 = mul nsw i32 %tmp, %tmp9
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%tmp11 = trunc i64 %indvars.iv23 to i32
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%tmp12 = srem i32 %tmp10, %tmp11
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%tmp13 = getelementptr inbounds i32, i32* %arg, i64 %indvars.iv23
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store i32 %tmp12, i32* %tmp13, align 4
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br label %for.first.latch
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for.first.latch: ; preds = %for.first
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%indvars.iv.next3 = add nuw nsw i64 %indvars.iv23, 1
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%tmp15 = add nuw nsw i32 %.014, 1
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%exitcond4 = icmp ne i64 %indvars.iv.next3, 100
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br i1 %exitcond4, label %for.first, label %for.second.preheader
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for.second.preheader: ; preds = %for.first.latch
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br label %for.second
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for.second: ; preds = %for.second.preheader, %for.second.latch
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%.02 = phi i32 [ 0, %for.second.preheader ], [ %tmp28, %for.second.latch ]
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%indvars.iv1 = phi i64 [ 3, %for.second.preheader ], [ %indvars.iv.next, %for.second.latch ]
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%tmp20 = add nsw i32 %.02, -3
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%tmp21 = add nuw nsw i64 %indvars.iv1, 3
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%tmp22 = trunc i64 %tmp21 to i32
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%tmp23 = mul nsw i32 %tmp20, %tmp22
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%tmp24 = trunc i64 %indvars.iv1 to i32
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%tmp25 = srem i32 %tmp23, %tmp24
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%tmp26 = getelementptr inbounds [1024 x i32], [1024 x i32]* @B, i64 0, i64 %indvars.iv1
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store i32 %tmp25, i32* %tmp26, align 4
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br label %for.second.latch
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for.second.latch: ; preds = %for.second
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%indvars.iv.next = add nuw nsw i64 %indvars.iv1, 1
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%tmp28 = add nuw nsw i32 %.02, 1
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%exitcond = icmp ne i64 %indvars.iv.next, 100
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br i1 %exitcond, label %for.second, label %for.end
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for.end: ; preds = %for.second.latch
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ret void
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}
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