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[JumpThreading] Conditionally freeze its condition when unfolding select
This patch fixes pr45956 (https://bugs.llvm.org/show_bug.cgi?id=45956 ). To minimize its impact to the quality of generated code, I suggest enabling this only for LTO as a start (it has two JumpThreading passes registered). This patch contains a flag that makes JumpThreading enable it. Reviewed By: efriedma Differential Revision: https://reviews.llvm.org/D84940
This commit is contained in:
Juneyoung Lee
parent
5d89de28a1
commit
e4e3a3311e
@ -240,10 +240,12 @@ FunctionPass *createReassociatePass();
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//===----------------------------------------------------------------------===//
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//
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// JumpThreading - Thread control through mult-pred/multi-succ blocks where some
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// preds always go to some succ. Thresholds other than minus one override the
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// internal BB duplication default threshold.
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// preds always go to some succ. If FreezeSelectCond is true, unfold the
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// condition of a select that unfolds to branch. Thresholds other than minus one
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// override the internal BB duplication default threshold.
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//
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FunctionPass *createJumpThreadingPass(int Threshold = -1);
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FunctionPass *createJumpThreadingPass(bool FreezeSelectCond = false,
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int Threshold = -1);
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//===----------------------------------------------------------------------===//
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//
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@ -91,9 +91,10 @@ class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
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unsigned BBDupThreshold;
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unsigned DefaultBBDupThreshold;
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bool InsertFreezeWhenUnfoldingSelect;
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public:
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JumpThreadingPass(int T = -1);
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JumpThreadingPass(bool InsertFreezeWhenUnfoldingSelect = false, int T = -1);
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// Glue for old PM.
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bool runImpl(Function &F, TargetLibraryInfo *TLI_, LazyValueInfo *LVI_,
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@ -104,6 +104,11 @@ static cl::opt<bool> PrintLVIAfterJumpThreading(
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cl::desc("Print the LazyValueInfo cache after JumpThreading"), cl::init(false),
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cl::Hidden);
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static cl::opt<bool> JumpThreadingFreezeSelectCond(
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"jump-threading-freeze-select-cond",
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cl::desc("Freeze the condition when unfolding select"), cl::init(false),
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cl::Hidden);
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static cl::opt<bool> ThreadAcrossLoopHeaders(
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"jump-threading-across-loop-headers",
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cl::desc("Allow JumpThreading to thread across loop headers, for testing"),
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@ -133,7 +138,8 @@ namespace {
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public:
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static char ID; // Pass identification
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JumpThreading(int T = -1) : FunctionPass(ID), Impl(T) {
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JumpThreading(bool InsertFreezeWhenUnfoldingSelect = false, int T = -1)
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: FunctionPass(ID), Impl(InsertFreezeWhenUnfoldingSelect, T) {
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initializeJumpThreadingPass(*PassRegistry::getPassRegistry());
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}
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@ -166,11 +172,12 @@ INITIALIZE_PASS_END(JumpThreading, "jump-threading",
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"Jump Threading", false, false)
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// Public interface to the Jump Threading pass
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FunctionPass *llvm::createJumpThreadingPass(int Threshold) {
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return new JumpThreading(Threshold);
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FunctionPass *llvm::createJumpThreadingPass(bool InsertFr, int Threshold) {
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return new JumpThreading(InsertFr, Threshold);
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}
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JumpThreadingPass::JumpThreadingPass(int T) {
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JumpThreadingPass::JumpThreadingPass(bool InsertFr, int T) {
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InsertFreezeWhenUnfoldingSelect = JumpThreadingFreezeSelectCond | InsertFr;
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DefaultBBDupThreshold = (T == -1) ? BBDuplicateThreshold : unsigned(T);
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}
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@ -2798,13 +2805,8 @@ bool JumpThreadingPass::TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB) {
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/// select is not jump-threaded, it will be folded again in the later
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/// optimizations.
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bool JumpThreadingPass::TryToUnfoldSelectInCurrBB(BasicBlock *BB) {
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// This transform can introduce a UB (a conditional branch that depends on a
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// poison value) that was not present in the original program. See
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// @TryToUnfoldSelectInCurrBB test in test/Transforms/JumpThreading/select.ll.
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// This transform would reduce the quality of msan diagnostics.
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// Disable this transform under MemorySanitizer.
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// FIXME: either delete it or replace with a valid transform. This issue is
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// not limited to MemorySanitizer (but has only been observed as an MSan false
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// positive in practice so far).
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if (BB->getParent()->hasFnAttribute(Attribute::SanitizeMemory))
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return false;
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@ -2852,8 +2854,11 @@ bool JumpThreadingPass::TryToUnfoldSelectInCurrBB(BasicBlock *BB) {
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if (!SI)
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continue;
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// Expand the select.
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Instruction *Term =
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SplitBlockAndInsertIfThen(SI->getCondition(), SI, false);
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Value *Cond = SI->getCondition();
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if (InsertFreezeWhenUnfoldingSelect &&
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!isGuaranteedNotToBeUndefOrPoison(Cond, SI, &DTU->getDomTree()))
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Cond = new FreezeInst(Cond, "cond.fr", SI);
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Instruction *Term = SplitBlockAndInsertIfThen(Cond, SI, false);
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BasicBlock *SplitBB = SI->getParent();
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BasicBlock *NewBB = Term->getParent();
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PHINode *NewPN = PHINode::Create(SI->getType(), 2, "", SI);
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248
test/Transforms/JumpThreading/select-unfold-freeze.ll
Normal file
248
test/Transforms/JumpThreading/select-unfold-freeze.ll
Normal file
@ -0,0 +1,248 @@
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -S -jump-threading-freeze-select-cond -jump-threading < %s | FileCheck %s
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declare void @foo()
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declare void @bar()
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declare void @baz()
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declare void @quux()
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define void @test_switch_cmp(i1 %cond, i32 %val, i8 %value) nounwind {
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; CHECK-LABEL: @test_switch_cmp(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[COND:%.*]], label [[L0:%.*]], label [[L0_THREAD:%.*]]
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; CHECK: L0:
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; CHECK-NEXT: [[VAL_PHI:%.*]] = phi i32 [ [[VAL:%.*]], [[ENTRY:%.*]] ]
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[VAL_PHI]], 0
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; CHECK-NEXT: [[COND_FR:%.*]] = freeze i1 [[CMP]]
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; CHECK-NEXT: br i1 [[COND_FR]], label [[L1:%.*]], label [[TMP0:%.*]]
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; CHECK: 0:
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; CHECK-NEXT: [[TMP1:%.*]] = phi i8 [ [[VALUE:%.*]], [[L0]] ]
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; CHECK-NEXT: switch i8 [[TMP1]], label [[L3:%.*]] [
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; CHECK-NEXT: i8 1, label [[L1]]
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; CHECK-NEXT: i8 2, label [[L2:%.*]]
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; CHECK-NEXT: ]
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; CHECK: L1:
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; CHECK-NEXT: call void @foo()
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; CHECK-NEXT: ret void
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; CHECK: L2:
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; CHECK-NEXT: call void @bar()
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; CHECK-NEXT: ret void
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; CHECK: L3:
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; CHECK-NEXT: call void @baz()
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; CHECK-NEXT: ret void
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; CHECK: L0.thread:
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; CHECK-NEXT: call void @quux()
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; CHECK-NEXT: br label [[L1]]
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;
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entry:
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br i1 %cond, label %L0, label %L4
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L0:
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%val.phi = phi i32 [%val, %entry], [-1, %L4]
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%cmp = icmp slt i32 %val.phi, 0
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%expr = select i1 %cmp, i8 1, i8 %value
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switch i8 %expr, label %L3 [i8 1, label %L1 i8 2, label %L2]
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L1:
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call void @foo()
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ret void
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L2:
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call void @bar()
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ret void
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L3:
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call void @baz()
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ret void
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L4:
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call void @quux()
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br label %L0
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}
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define i32 @unfold3(i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z, i32 %j) nounwind {
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; CHECK-LABEL: @unfold3(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[ADD3:%.*]] = add nsw i32 [[J:%.*]], 2
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; CHECK-NEXT: [[CMP_I:%.*]] = icmp slt i32 [[U:%.*]], [[V:%.*]]
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; CHECK-NEXT: br i1 [[CMP_I]], label [[DOTEXIT_THREAD4:%.*]], label [[COND_FALSE_I:%.*]]
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; CHECK: cond.false.i:
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; CHECK-NEXT: [[CMP4_I:%.*]] = icmp sgt i32 [[U]], [[V]]
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; CHECK-NEXT: br i1 [[CMP4_I]], label [[DOTEXIT_THREAD:%.*]], label [[COND_FALSE_6_I:%.*]]
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; CHECK: cond.false.6.i:
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; CHECK-NEXT: [[CMP8_I:%.*]] = icmp slt i32 [[W:%.*]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP8_I]], label [[DOTEXIT_THREAD4]], label [[COND_FALSE_10_I:%.*]]
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; CHECK: cond.false.10.i:
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; CHECK-NEXT: [[CMP13_I:%.*]] = icmp sgt i32 [[W]], [[X]]
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; CHECK-NEXT: br i1 [[CMP13_I]], label [[DOTEXIT_THREAD]], label [[DOTEXIT:%.*]]
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; CHECK: .exit:
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; CHECK-NEXT: [[PHITMP:%.*]] = icmp sge i32 [[Y:%.*]], [[Z:%.*]]
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; CHECK-NEXT: [[COND_FR:%.*]] = freeze i1 [[PHITMP]]
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; CHECK-NEXT: br i1 [[COND_FR]], label [[DOTEXIT_THREAD]], label [[DOTEXIT_THREAD4]]
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; CHECK: .exit.thread:
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; CHECK-NEXT: br label [[DOTEXIT_THREAD4]]
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; CHECK: .exit.thread4:
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; CHECK-NEXT: [[TMP0:%.*]] = phi i32 [ [[J]], [[DOTEXIT_THREAD]] ], [ [[ADD3]], [[DOTEXIT]] ], [ [[ADD3]], [[ENTRY:%.*]] ], [ [[ADD3]], [[COND_FALSE_6_I]] ]
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; CHECK-NEXT: ret i32 [[TMP0]]
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;
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entry:
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%add3 = add nsw i32 %j, 2
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%cmp.i = icmp slt i32 %u, %v
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br i1 %cmp.i, label %.exit, label %cond.false.i
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cond.false.i: ; preds = %entry
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%cmp4.i = icmp sgt i32 %u, %v
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br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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cond.false.6.i: ; preds = %cond.false.i
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%cmp8.i = icmp slt i32 %w, %x
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br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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cond.false.10.i: ; preds = %cond.false.6.i
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%cmp13.i = icmp sgt i32 %w, %x
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br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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cond.false.15.i: ; preds = %cond.false.10.i
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%phitmp = icmp sge i32 %y, %z
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br label %.exit
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.exit: ; preds = %entry, %cond.false.i, %cond.false.6.i, %cond.false.10.i, %cond.false.15.i
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%cond23.i = phi i1 [ false, %entry ], [ true, %cond.false.i ], [ false, %cond.false.6.i ], [ %phitmp, %cond.false.15.i ], [ true, %cond.false.10.i ]
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%j.add3 = select i1 %cond23.i, i32 %j, i32 %add3
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ret i32 %j.add3
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}
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define i32 @unfold4(i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z, i32 %j) nounwind {
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; CHECK-LABEL: @unfold4(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[ADD3:%.*]] = add nsw i32 [[J:%.*]], 2
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; CHECK-NEXT: [[CMP_I:%.*]] = icmp slt i32 [[U:%.*]], [[V:%.*]]
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; CHECK-NEXT: br i1 [[CMP_I]], label [[DOTEXIT_THREAD:%.*]], label [[COND_FALSE_I:%.*]]
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; CHECK: cond.false.i:
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; CHECK-NEXT: [[CMP4_I:%.*]] = icmp sgt i32 [[U]], [[V]]
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; CHECK-NEXT: br i1 [[CMP4_I]], label [[DOTEXIT_THREAD5:%.*]], label [[COND_FALSE_6_I:%.*]]
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; CHECK: cond.false.6.i:
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; CHECK-NEXT: [[CMP8_I:%.*]] = icmp slt i32 [[W:%.*]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP8_I]], label [[DOTEXIT_THREAD]], label [[COND_FALSE_10_I:%.*]]
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; CHECK: cond.false.10.i:
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; CHECK-NEXT: [[CMP13_I:%.*]] = icmp sgt i32 [[W]], [[X]]
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; CHECK-NEXT: br i1 [[CMP13_I]], label [[DOTEXIT_THREAD5]], label [[DOTEXIT:%.*]]
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; CHECK: .exit:
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; CHECK-NEXT: [[CMP19_I:%.*]] = icmp sge i32 [[Y:%.*]], [[Z:%.*]]
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; CHECK-NEXT: [[CONV:%.*]] = zext i1 [[CMP19_I]] to i32
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; CHECK-NEXT: [[LNOT_I18:%.*]] = icmp eq i32 [[CONV]], 1
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; CHECK-NEXT: [[COND_FR:%.*]] = freeze i1 [[LNOT_I18]]
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; CHECK-NEXT: br i1 [[COND_FR]], label [[DOTEXIT_THREAD]], label [[DOTEXIT_THREAD5]]
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; CHECK: .exit.thread:
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; CHECK-NEXT: br label [[DOTEXIT_THREAD5]]
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; CHECK: .exit.thread5:
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; CHECK-NEXT: [[TMP0:%.*]] = phi i32 [ [[J]], [[DOTEXIT_THREAD]] ], [ [[ADD3]], [[DOTEXIT]] ], [ [[ADD3]], [[COND_FALSE_I]] ], [ [[ADD3]], [[COND_FALSE_10_I]] ]
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; CHECK-NEXT: ret i32 [[TMP0]]
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;
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entry:
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%add3 = add nsw i32 %j, 2
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%cmp.i = icmp slt i32 %u, %v
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br i1 %cmp.i, label %.exit, label %cond.false.i
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cond.false.i: ; preds = %entry
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%cmp4.i = icmp sgt i32 %u, %v
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br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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cond.false.6.i: ; preds = %cond.false.i
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%cmp8.i = icmp slt i32 %w, %x
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br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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cond.false.10.i: ; preds = %cond.false.6.i
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%cmp13.i = icmp sgt i32 %w, %x
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br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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cond.false.15.i: ; preds = %cond.false.10.i
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%cmp19.i = icmp sge i32 %y, %z
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%conv = zext i1 %cmp19.i to i32
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br label %.exit
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.exit: ; preds = %entry, %cond.false.i, %cond.false.6.i, %cond.false.10.i, %cond.false.15.i
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%cond23.i = phi i32 [ 1, %entry ], [ 0, %cond.false.i ], [ 1, %cond.false.6.i ], [ %conv, %cond.false.15.i ], [ 0, %cond.false.10.i ]
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%lnot.i18 = icmp eq i32 %cond23.i, 1
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%j.add3 = select i1 %lnot.i18, i32 %j, i32 %add3
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ret i32 %j.add3
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}
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; TODO: cond23_i should be constant-folded.
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define i32 @unfold5(i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z, i32 %j) nounwind {
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; CHECK-LABEL: @unfold5(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[ADD3:%.*]] = add nsw i32 [[J:%.*]], 2
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; CHECK-NEXT: [[CMP_I:%.*]] = icmp slt i32 [[U:%.*]], [[V:%.*]]
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; CHECK-NEXT: br i1 [[CMP_I]], label [[DOTEXIT_THREAD:%.*]], label [[COND_FALSE_I:%.*]]
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; CHECK: cond.false.i:
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; CHECK-NEXT: [[CMP4_I:%.*]] = icmp sgt i32 [[U]], [[V]]
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; CHECK-NEXT: br i1 [[CMP4_I]], label [[DOTEXIT_THREAD]], label [[COND_FALSE_6_I:%.*]]
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; CHECK: cond.false.6.i:
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; CHECK-NEXT: [[CMP8_I:%.*]] = icmp slt i32 [[W:%.*]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP8_I]], label [[DOTEXIT_THREAD]], label [[COND_FALSE_10_I:%.*]]
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; CHECK: cond.false.10.i:
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; CHECK-NEXT: [[CMP13_I:%.*]] = icmp sgt i32 [[W]], [[X]]
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; CHECK-NEXT: br i1 [[CMP13_I]], label [[TMP0:%.*]], label [[COND_FALSE_15_I:%.*]]
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; CHECK: cond.false.15.i:
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; CHECK-NEXT: [[CMP19_I:%.*]] = icmp sge i32 [[Y:%.*]], [[Z:%.*]]
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; CHECK-NEXT: [[CONV:%.*]] = zext i1 [[CMP19_I]] to i32
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; CHECK-NEXT: br label [[DOTEXIT_THREAD]]
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; CHECK: 0:
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; CHECK-NEXT: [[COND23_I:%.*]] = phi i32 [ 7, [[COND_FALSE_10_I]] ]
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; CHECK-NEXT: [[LNOT_I18:%.*]] = icmp sgt i32 [[COND23_I]], 5
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; CHECK-NEXT: br label [[DOTEXIT_THREAD]]
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; CHECK: .exit.thread:
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; CHECK-NEXT: [[TMP1:%.*]] = phi i32 [ [[J]], [[TMP0]] ], [ [[CONV]], [[COND_FALSE_15_I]] ], [ 1, [[COND_FALSE_6_I]] ], [ 3, [[COND_FALSE_I]] ], [ 2, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret i32 [[TMP1]]
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;
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entry:
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%add3 = add nsw i32 %j, 2
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%cmp.i = icmp slt i32 %u, %v
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br i1 %cmp.i, label %.exit, label %cond.false.i
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cond.false.i: ; preds = %entry
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%cmp4.i = icmp sgt i32 %u, %v
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br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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cond.false.6.i: ; preds = %cond.false.i
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%cmp8.i = icmp slt i32 %w, %x
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br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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cond.false.10.i: ; preds = %cond.false.6.i
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%cmp13.i = icmp sgt i32 %w, %x
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br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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cond.false.15.i: ; preds = %cond.false.10.i
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%cmp19.i = icmp sge i32 %y, %z
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%conv = zext i1 %cmp19.i to i32
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br label %.exit
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.exit: ; preds = %entry, %cond.false.i, %cond.false.6.i, %cond.false.10.i, %cond.false.15.i
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%cond23.i = phi i32 [ 2, %entry ], [ 3, %cond.false.i ], [ 1, %cond.false.6.i ], [ %conv, %cond.false.15.i ], [ 7, %cond.false.10.i ]
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%lnot.i18 = icmp sgt i32 %cond23.i, 5
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%j.add3 = select i1 %lnot.i18, i32 %j, i32 %cond23.i
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ret i32 %j.add3
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}
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define i32 @TryToUnfoldSelectInCurrBB(i1 %b, i1 %ui, i32 %s, i1 %x) {
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; CHECK-LABEL: @TryToUnfoldSelectInCurrBB(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br i1 [[B:%.*]], label [[IF_END_THREAD:%.*]], label [[IF_END:%.*]]
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; CHECK: if.end:
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; CHECK-NEXT: [[COND_FR:%.*]] = freeze i1 [[X:%.*]]
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; CHECK-NEXT: br i1 [[COND_FR]], label [[TMP0:%.*]], label [[IF_END_THREAD]]
|
||||
; CHECK: 0:
|
||||
; CHECK-NEXT: br label [[IF_END_THREAD]]
|
||||
; CHECK: if.end.thread:
|
||||
; CHECK-NEXT: [[TMP1:%.*]] = phi i32 [ [[S:%.*]], [[TMP0]] ], [ 42, [[IF_END]] ], [ 42, [[ENTRY:%.*]] ]
|
||||
; CHECK-NEXT: ret i32 [[TMP1]]
|
||||
;
|
||||
entry:
|
||||
br i1 %b, label %if.end, label %if.else
|
||||
|
||||
if.else:
|
||||
br label %if.end
|
||||
|
||||
if.end:
|
||||
%v = phi i1 [ %x, %if.else ], [ false, %entry ]
|
||||
%v1 = select i1 %v, i32 %s, i32 42
|
||||
ret i32 %v1
|
||||
}
|
||||
Loading…
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Reference in New Issue
Block a user