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[LoopSimplifyCFG] Fix corner case with duplicating successors

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It fixes a bug that doesn't update Phi inputs of the only live successor that
is in the list of block's successors more than once.

Thanks @uabelho for finding this.

Differential Revision: https://reviews.llvm.org/D54849
Reviewed By: anna

llvm-svn: 347640
This commit is contained in:
Max Kazantsev 2018-11-27 06:17:21 +00:00
parent cc3d32505c
commit eecd54872d
2 changed files with 25 additions and 4 deletions
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12
lib/Transforms/Scalar/LoopSimplifyCFG.cpp
View File

@ -249,6 +249,7 @@ private:
SmallPtrSet<BasicBlock *, 2> DeadSuccessors;
// Remove all BB's successors except for the live one.
unsigned TheOnlySuccDuplicates = 0;
for (auto *Succ : successors(BB))
if (Succ != TheOnlySucc) {
DeadSuccessors.insert(Succ);
@ -256,7 +257,16 @@ private:
// the one-input Phi because it is a LCSSA Phi.
bool PreserveLCSSAPhi = !L.contains(Succ);
Succ->removePredecessor(BB, PreserveLCSSAPhi);
}
} else
++TheOnlySuccDuplicates;
assert(TheOnlySuccDuplicates > 0 && "Should be!");
// If TheOnlySucc was BB's successor more than once, after transform it
// will be its successor only once. Remove redundant inputs from
// TheOnlySucc's Phis.
bool PreserveLCSSAPhi = !L.contains(TheOnlySucc);
for (unsigned Dup = 1; Dup < TheOnlySuccDuplicates; ++Dup)
TheOnlySucc->removePredecessor(BB, PreserveLCSSAPhi);
IRBuilder<> Builder(BB->getContext());
Instruction *Term = BB->getTerminator();

17
test/Transforms/LoopSimplifyCFG/phi_with_duplicating_inputs.ll
View File

@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; This is currently failing because of bug in LoopSimplifyCFG. It does not update
; duplicating Phi inputs properly.
; XFAIL: *
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -passes='require<domtree>,loop(simplify-cfg)' -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
; RUN: opt -S -enable-loop-simplifycfg-term-folding=true -loop-simplifycfg -enable-mssa-loop-dependency=true -verify-memoryssa -debug-only=loop-simplifycfg -verify-loop-info -verify-dom-info -verify-loop-lcssa 2>&1 < %s | FileCheck %s
@ -9,9 +9,20 @@ target datalayout = "P40"
@a = external global i16, align 1
; CHECK-LABEL: @f1(
define void @f1(i1 %cond) {
; CHECK-LABEL: @f1(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_COND:%.*]]
; CHECK: for.cond:
; CHECK-NEXT: br i1 [[COND:%.*]], label [[IF_THEN:%.*]], label [[FOR_INC:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[TMP0:%.*]] = load i16, i16* @a, align 1
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp ne i16 [[TMP0]], 0
; CHECK-NEXT: br label [[FOR_INC]]
; CHECK: for.inc:
; CHECK-NEXT: [[C_1:%.*]] = phi i16 [ 2, [[IF_THEN]] ], [ 1, [[FOR_COND]] ]
; CHECK-NEXT: br label [[FOR_COND]]
;
entry:
br label %for.cond