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[LoopFusion] Update second loop guard non loop successor phis incoming 

blocks.

Summary: The current LoopFusion forget to update the incoming block of
the phis in second loop guard non loop successor from second loop guard
block to first loop guard block. A test case is provided to better
understand the problem.
Reviewed By: jdoerfert
Subscribers: hiraditya, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D81421
This commit is contained in:
Whitney Tsang 2020-06-09 21:12:51 +00:00
parent a27d385209
commit 01e64c9712
2 changed files with 60 additions and 0 deletions
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1
llvm/lib/Transforms/Scalar/LoopFuse.cpp
View File

@ -1385,6 +1385,7 @@ private:
// Thus, one path from the guard goes to the preheader for FC0 (and thus
// executes the new fused loop) and the other path goes to the NonLoopBlock
// for FC1 (where FC1 guard would have gone if FC1 was not executed).
FC1NonLoopBlock->replacePhiUsesWith(FC1GuardBlock, FC0GuardBlock);
FC0.GuardBranch->replaceUsesOfWith(FC0NonLoopBlock, FC1NonLoopBlock);
FC0.ExitBlock->getTerminator()->replaceUsesOfWith(FC1GuardBlock,
FC1.Header);

59
llvm/test/Transforms/LoopFusion/guarded.ll
View File

@ -232,3 +232,62 @@ for.second.exit:
for.end:
ret void
}
; Test that the incoming block of `%j.lcssa` is updated correctly
; from for.second.guard to for.first.guard, and the two loops for.first and
; for.second are fused.
; CHECK: i64 @updatephi_guardnonloopblock
; CHECK-LABEL: for.first.guard:
; CHECK-NEXT: %cmp.guard = icmp slt i64 0, %N
; CHECK: br i1 %cmp.guard, label %for.first.preheader, label %for.end
; CHECK-LABEL: for.first.preheader:
; CHECK-NEXT: br label %for.first
; CHECK-LABEL: for.first:
; CHECK: br i1 %cmp.j, label %for.first, label %for.second.exit
; CHECK-LABEL: for.second.exit:
; CHECK-NEXT: br label %for.end
; CHECK-LABEL: for.end:
; CHECK-NEXT: %j.lcssa = phi i64 [ 0, %for.first.guard ], [ %j.02, %for.second.exit ]
; CHECK-NEXT: ret i64 %j.lcssa
define i64 @updatephi_guardnonloopblock(i32* noalias %A, i32* noalias %B, i64 %N, i32 %x) {
for.first.guard:
%cmp.guard = icmp slt i64 0, %N
br i1 %cmp.guard, label %for.first.preheader, label %for.second.guard
for.first.preheader:
br label %for.first
for.first:
%i.04 = phi i64 [ %inc, %for.first ], [ 0, %for.first.preheader ]
%arrayidx = getelementptr inbounds i32, i32* %A, i64 %i.04
store i32 0, i32* %arrayidx, align 4
%inc = add nsw i64 %i.04, 1
%cmp = icmp slt i64 %inc, %N
br i1 %cmp, label %for.first, label %for.first.exit
for.first.exit:
br label %for.second.guard
for.second.guard:
br i1 %cmp.guard, label %for.second.preheader, label %for.end
for.second.preheader:
br label %for.second
for.second:
%j.02 = phi i64 [ %inc6, %for.second ], [ 0, %for.second.preheader ]
%arrayidx4 = getelementptr inbounds i32, i32* %B, i64 %j.02
store i32 0, i32* %arrayidx4, align 4
%inc6 = add nsw i64 %j.02, 1
%cmp.j = icmp slt i64 %inc6, %N
br i1 %cmp.j, label %for.second, label %for.second.exit
for.second.exit:
br label %for.end
for.end:
%j.lcssa = phi i64 [ 0, %for.second.guard ], [ %j.02, %for.second.exit ]
ret i64 %j.lcssa
}