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[LoopUnrollRuntime] Bailout when multiple exiting blocks to the unique latch exit block 

Currently, we do not support multiple exiting blocks to the
latch exit block. However, this bailout wasn't triggered when we had a
unique exit block (which is the latch exit), with multiple exiting
blocks to that unique exit.

Moved the bailout so that it's triggered in both cases and added
testcase.

llvm-svn: 307291
This commit is contained in:
Anna Thomas 2017-07-06 18:39:26 +00:00
parent 47c8f66997
commit eb6d5d1950
2 changed files with 35 additions and 4 deletions
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9
llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
View File

@ -504,10 +504,6 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// transformed. // transformed.
if (!PreserveLCSSA) if (!PreserveLCSSA)
return false; return false;
// TODO: Support multiple exiting blocks jumping to the `LatchExit`. This
// will need updating the logic in connectEpilog.
if (!LatchExit->getSinglePredecessor())
return false;
SmallVector<BasicBlock *, 4> Exits; SmallVector<BasicBlock *, 4> Exits;
L->getUniqueExitBlocks(Exits); L->getUniqueExitBlocks(Exits);
for (auto *BB : Exits) for (auto *BB : Exits)
@ -517,6 +513,11 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
assert(LatchExit && "Latch Exit should exist!"); assert(LatchExit && "Latch Exit should exist!");
// TODO: Support multiple exiting blocks jumping to the `LatchExit` when
// UnrollRuntimeMultiExit is true. This will need updating the logic in
// connectEpilog.
if (!LatchExit->getSinglePredecessor())
return false;
// Use Scalar Evolution to compute the trip count. This allows more loops to // Use Scalar Evolution to compute the trip count. This allows more loops to
// be unrolled than relying on induction var simplification. // be unrolled than relying on induction var simplification.
if (!SE) if (!SE)

30
llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
View File

@ -184,6 +184,36 @@ for.exit2:
ret i32 42 ret i32 42
} }
; FIXME: Support multiple exiting blocks to the unique exit block.
define void @unique_exit(i32 %arg) {
; CHECK-LABEL: unique_exit
; CHECK-NOT: .unr
; CHECK-NOT: .epil
entry:
%tmp = icmp sgt i32 undef, %arg
br i1 %tmp, label %preheader, label %returnblock
preheader: ; preds = %entry
br label %header
LoopExit: ; preds = %header, %latch
%tmp2.ph = phi i32 [ %tmp4, %header ], [ -1, %latch ]
br label %returnblock
returnblock: ; preds = %LoopExit, %entry
%tmp2 = phi i32 [ -1, %entry ], [ %tmp2.ph, %LoopExit ]
ret void
header: ; preds = %preheader, %latch
%tmp4 = phi i32 [ %inc, %latch ], [ %arg, %preheader ]
%inc = add nsw i32 %tmp4, 1
br i1 true, label %LoopExit, label %latch
latch: ; preds = %header
%cmp = icmp slt i32 %inc, undef
br i1 %cmp, label %header, label %LoopExit
}
; two exiting and two exit blocks. ; two exiting and two exit blocks.
; the non-latch exiting block has duplicate edges to the non-latch exit block. ; the non-latch exiting block has duplicate edges to the non-latch exit block.
define i64 @test5(i64 %trip, i64 %add, i1 %cond) { define i64 @test5(i64 %trip, i64 %add, i1 %cond) {