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[LoopSimplify] Fix updating LCSSA after separating nested loops.

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This fixes PR28825. The problem was that we only checked if a value from
a created inner loop is used in the outer loop, and fixed LCSSA for
them. But we missed to fixup LCSSA for values used in exits of the outer
loop.

llvm-svn: 277877
This commit is contained in:
Michael Zolotukhin 2016-08-05 21:52:58 +00:00
parent d023c59def
commit fa30ea5db2
2 changed files with 48 additions and 1 deletions
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15
lib/Transforms/Utils/LoopSimplify.cpp
View File

@ -376,6 +376,21 @@ static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
}
}
}
// We also need to check exit blocks of the outer loop - it might be using
// values from what now became an inner loop.
SmallVector<BasicBlock*, 8> ExitBlocks;
NewOuter->getExitBlocks(ExitBlocks);
for (BasicBlock *ExitBB: ExitBlocks) {
for (Instruction &I : *ExitBB) {
for (Value *Op : I.operands()) {
Instruction *OpI = dyn_cast<Instruction>(Op);
if (!OpI || !L->contains(OpI))
continue;
WorklistSet.insert(OpI);
}
}
}
SmallVector<Instruction *, 8> Worklist(WorklistSet.begin(),
WorklistSet.end());
formLCSSAForInstructions(Worklist, *DT, *LI);

34
test/Transforms/LoopSimplify/pr28272.ll
View File

@ -1,7 +1,7 @@
; RUN: opt < %s -lcssa -loop-unroll -S | FileCheck %s
target triple = "x86_64-unknown-linux-gnu"
; PR28272
; PR28272, PR28825
; When LoopSimplify separates nested loops, it might break LCSSA form: values
; from the original loop might be used in the outer loop. This test invokes
; loop-unroll, which calls loop-simplify before itself. If LCSSA is broken
@ -74,3 +74,35 @@ loop2.if.false:
bb:
br label %loop2
}
; When LoopSimplify separates nested loops, it might break LCSSA form: values
; from the original loop might be used in exit blocks of the outer loop.
; CHECK-LABEL: @foo3
define void @foo3() {
entry:
br label %bb1
bb1:
br i1 undef, label %bb2, label %bb1
bb2:
%a = phi i32 [ undef, %bb1 ], [ %a, %bb3 ], [ undef, %bb5 ]
br i1 undef, label %bb3, label %bb1
bb3:
%b = load i32*, i32** undef
br i1 undef, label %bb2, label %bb4
bb4:
br i1 undef, label %bb5, label %bb6
bb5:
br i1 undef, label %bb2, label %bb4
bb6:
br i1 undef, label %bb_end, label %bb1
bb_end:
%x = getelementptr i32, i32* %b
br label %bb_end
}