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[LoopSimplifyCFG] Form LCSSA when a parent loop becomes a sibling

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During the transforms in LoopSimplifyCFG, when we remove a dead exiting edge, the
parent loop may stop being reachable from the child loop, and therefore they become
siblings. If the former child loop had uses of some values from its former parent loop,
now such uses will require LCSSA Phis, even if they weren't needed before. So we must
form LCSSA for all loops that stopped being ancestors of the current loop in this case.

Differential Revision: https://reviews.llvm.org/D56144
Reviewed By: fedor.sergeev


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351434 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Max Kazantsev
2019-01-17 12:51:10 +00:00
parent 5865df5baa
commit a3ca8ce0e5
2 changed files with 27 additions and 3 deletions
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lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+9
View File
@@ -379,6 +379,15 @@ private:
StillReachable->addChildLoop(&L);
else
LI.addTopLevelLoop(&L);
// Some values from loops in [OuterLoop, StillReachable) could be used
// in the current loop. Now it is not their child anymore, so such uses
// require LCSSA Phis.
Loop *FixLCSSALoop = OuterLoop;
while (FixLCSSALoop->getParentLoop() != StillReachable)
FixLCSSALoop = FixLCSSALoop->getParentLoop();
assert(FixLCSSALoop && "Should be a loop!");
formLCSSARecursively(*FixLCSSALoop, DT, &LI, &SE);
}
}
}
test/Transforms/LoopSimplifyCFG/lcssa.ll
+18 -3
View File
@@ -3,9 +3,6 @@
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(simplify-cfg)' -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -enable-mssa-loop-dependency=true -verify-memoryssa -verify-loop-info -verify-dom-info -verify-loop-lcssa < %s | FileCheck %s
; XFAIL: *
; test_01 is currently failing because the loop is not in LCSSA form after the
; transform.
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
@@ -56,6 +53,24 @@ if.end.8: ; preds = %if.end.7
}
define void @test_01() {
; CHECK-LABEL: @test_01(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_COND:%.*]]
; CHECK: for.cond.loopexit:
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.cond:
; CHECK-NEXT: [[INC41_LCSSA3:%.*]] = phi i16 [ undef, [[FOR_COND_LOOPEXIT:%.*]] ], [ undef, [[ENTRY:%.*]] ]
; CHECK-NEXT: switch i32 0, label [[FOR_COND_SPLIT:%.*]] [
; CHECK-NEXT: i32 1, label [[FOR_COND_LOOPEXIT]]
; CHECK-NEXT: ]
; CHECK: for.cond-split:
; CHECK-NEXT: [[INC41_LCSSA3_LCSSA:%.*]] = phi i16 [ [[INC41_LCSSA3]], [[FOR_COND]] ]
; CHECK-NEXT: br label [[WHILE_COND:%.*]]
; CHECK: while.cond:
; CHECK-NEXT: [[INC41:%.*]] = phi i16 [ [[INC4:%.*]], [[WHILE_COND]] ], [ [[INC41_LCSSA3_LCSSA]], [[FOR_COND_SPLIT]] ]
; CHECK-NEXT: [[INC4]] = add nsw i16 [[INC41]], 1
; CHECK-NEXT: br label [[WHILE_COND]]
;
entry:
br label %for.cond