maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[SimpleLoopUnswitch] Skip trivial selects during trivial unswitching. 

Update the remaining places in unswitchTrivialBranch to properly skip
trivial selects.

Fixes #55526.
This commit is contained in:
Florian Hahn 2022-05-19 17:01:11 +01:00
parent d14f2a6359
commit 32d6ef36d6
No known key found for this signature in database
GPG Key ID: CF59919C6547A668
2 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
View File

@ -460,12 +460,12 @@ static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT,
// some input conditions to the branch.
bool FullUnswitch = false;
if (L.isLoopInvariant(BI.getCondition())) {
Invariants.push_back(BI.getCondition());
Value *Cond = skipTrivialSelect(BI.getCondition());
if (L.isLoopInvariant(Cond)) {
Invariants.push_back(Cond);
FullUnswitch = true;
} else {
if (auto *CondInst =
dyn_cast<Instruction>(skipTrivialSelect(BI.getCondition())))
if (auto *CondInst = dyn_cast<Instruction>(Cond))
Invariants = collectHomogenousInstGraphLoopInvariants(L, *CondInst, LI);
if (Invariants.empty()) {
LLVM_DEBUG(dbgs() << " Couldn't find invariant inputs!\n");
@ -499,7 +499,6 @@ static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT,
// is a graph of `or` operations, or the exit block is along the false edge
// and the condition is a graph of `and` operations.
if (!FullUnswitch) {
Value *Cond = skipTrivialSelect(BI.getCondition());
if (ExitDirection ? !match(Cond, m_LogicalOr())
: !match(Cond, m_LogicalAnd())) {
LLVM_DEBUG(dbgs() << " Branch condition is in improper form for "
@ -566,6 +565,7 @@ static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT,
// its successors.
OldPH->getInstList().splice(OldPH->end(), BI.getParent()->getInstList(),
BI);
BI.setCondition(Cond);
if (MSSAU) {
// Temporarily clone the terminator, to make MSSA update cheaper by
// separating "insert edge" updates from "remove edge" ones.
@ -1040,7 +1040,8 @@ static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT,
// Don't bother trying to unswitch past an unconditional branch or a branch
// with a constant value. These should be removed by simplifycfg prior to
// running this pass.
if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
if (!BI->isConditional() ||
isa<Constant>(skipTrivialSelect(BI->getCondition())))
return Changed;
// Found a trivial condition candidate: non-foldable conditional branch. If

26
llvm/test/Transforms/SimpleLoopUnswitch/trivial-unswitch-logical-and-or.ll
View File

@ -248,3 +248,29 @@ do_something:
loop_exit:
ret i32 0
}
; Test case for PR55526.
define void @test_pr55526(i16 %a) {
; CHECK-LABEL: @test_pr55526(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp ne i16 [[A:%.*]], 0
; CHECK-NEXT: br i1 [[TOBOOL]], label [[ENTRY_SPLIT:%.*]], label [[EXIT:%.*]]
; CHECK: entry.split:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[SEL:%.*]] = select i1 true, i1 true, i1 false
; CHECK-NEXT: br label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%tobool = icmp ne i16 %a, 0
br label %loop
loop:
%sel = select i1 %tobool, i1 true, i1 false
br i1 %sel, label %loop, label %exit
exit:
ret void
}