[llvm] 1e3c6fc - [JumpThreading] Ignore free instructions
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 23 09:28:43 PDT 2021
Author: Nikita Popov
Date: 2021-09-23T18:28:36+02:00
New Revision: 1e3c6fc7cb9d2ee6a5328881f95d6643afeadbff
URL: https://github.com/llvm/llvm-project/commit/1e3c6fc7cb9d2ee6a5328881f95d6643afeadbff
DIFF: https://github.com/llvm/llvm-project/commit/1e3c6fc7cb9d2ee6a5328881f95d6643afeadbff.diff
LOG: [JumpThreading] Ignore free instructions
This is basically D108837 but for jump threading. Free instructions
should be ignored for the threading decision. JumpThreading already
skips some free instructions (like pointer bitcasts), but does not
skip various free intrinsics -- in fact, it currently gives them a
fairly large cost of 2.
Differential Revision: https://reviews.llvm.org/D110290
Added:
Modified:
llvm/include/llvm/Transforms/Scalar/JumpThreading.h
llvm/lib/Transforms/Scalar/JumpThreading.cpp
llvm/test/Transforms/JumpThreading/free_instructions.ll
llvm/test/Transforms/PhaseOrdering/inlining-alignment-assumptions.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
index 816ea1071e52b..0ac7d7c62b7a3 100644
--- a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
+++ b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -44,6 +44,7 @@ class PHINode;
class SelectInst;
class SwitchInst;
class TargetLibraryInfo;
+class TargetTransformInfo;
class Value;
/// A private "module" namespace for types and utilities used by
@@ -78,6 +79,7 @@ enum ConstantPreference { WantInteger, WantBlockAddress };
/// revectored to the false side of the second if.
class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
TargetLibraryInfo *TLI;
+ TargetTransformInfo *TTI;
LazyValueInfo *LVI;
AAResults *AA;
DomTreeUpdater *DTU;
@@ -99,9 +101,9 @@ class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
JumpThreadingPass(bool InsertFreezeWhenUnfoldingSelect = false, int T = -1);
// Glue for old PM.
- bool runImpl(Function &F, TargetLibraryInfo *TLI, LazyValueInfo *LVI,
- AAResults *AA, DomTreeUpdater *DTU, bool HasProfileData,
- std::unique_ptr<BlockFrequencyInfo> BFI,
+ bool runImpl(Function &F, TargetLibraryInfo *TLI, TargetTransformInfo *TTI,
+ LazyValueInfo *LVI, AAResults *AA, DomTreeUpdater *DTU,
+ bool HasProfileData, std::unique_ptr<BlockFrequencyInfo> BFI,
std::unique_ptr<BranchProbabilityInfo> BPI);
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 688902ecb9ff6..fe9a7211967c4 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -331,7 +331,7 @@ bool JumpThreading::runOnFunction(Function &F) {
BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
}
- bool Changed = Impl.runImpl(F, TLI, LVI, AA, &DTU, F.hasProfileData(),
+ bool Changed = Impl.runImpl(F, TLI, TTI, LVI, AA, &DTU, F.hasProfileData(),
std::move(BFI), std::move(BPI));
if (PrintLVIAfterJumpThreading) {
dbgs() << "LVI for function '" << F.getName() << "':\n";
@@ -360,7 +360,7 @@ PreservedAnalyses JumpThreadingPass::run(Function &F,
BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
}
- bool Changed = runImpl(F, &TLI, &LVI, &AA, &DTU, F.hasProfileData(),
+ bool Changed = runImpl(F, &TLI, &TTI, &LVI, &AA, &DTU, F.hasProfileData(),
std::move(BFI), std::move(BPI));
if (PrintLVIAfterJumpThreading) {
@@ -377,12 +377,14 @@ PreservedAnalyses JumpThreadingPass::run(Function &F,
}
bool JumpThreadingPass::runImpl(Function &F, TargetLibraryInfo *TLI_,
- LazyValueInfo *LVI_, AliasAnalysis *AA_,
- DomTreeUpdater *DTU_, bool HasProfileData_,
+ TargetTransformInfo *TTI_, LazyValueInfo *LVI_,
+ AliasAnalysis *AA_, DomTreeUpdater *DTU_,
+ bool HasProfileData_,
std::unique_ptr<BlockFrequencyInfo> BFI_,
std::unique_ptr<BranchProbabilityInfo> BPI_) {
LLVM_DEBUG(dbgs() << "Jump threading on function '" << F.getName() << "'\n");
TLI = TLI_;
+ TTI = TTI_;
LVI = LVI_;
AA = AA_;
DTU = DTU_;
@@ -514,7 +516,8 @@ static void replaceFoldableUses(Instruction *Cond, Value *ToVal) {
/// Return the cost of duplicating a piece of this block from first non-phi
/// and before StopAt instruction to thread across it. Stop scanning the block
/// when exceeding the threshold. If duplication is impossible, returns ~0U.
-static unsigned getJumpThreadDuplicationCost(BasicBlock *BB,
+static unsigned getJumpThreadDuplicationCost(const TargetTransformInfo *TTI,
+ BasicBlock *BB,
Instruction *StopAt,
unsigned Threshold) {
assert(StopAt->getParent() == BB && "Not an instruction from proper BB?");
@@ -550,26 +553,21 @@ static unsigned getJumpThreadDuplicationCost(BasicBlock *BB,
if (Size > Threshold)
return Size;
- // Debugger intrinsics don't incur code size.
- if (isa<DbgInfoIntrinsic>(I)) continue;
-
- // Pseudo-probes don't incur code size.
- if (isa<PseudoProbeInst>(I))
- continue;
-
- // If this is a pointer->pointer bitcast, it is free.
- if (isa<BitCastInst>(I) && I->getType()->isPointerTy())
- continue;
-
- // Freeze instruction is free, too.
- if (isa<FreezeInst>(I))
- continue;
-
// Bail out if this instruction gives back a token type, it is not possible
// to duplicate it if it is used outside this BB.
if (I->getType()->isTokenTy() && I->isUsedOutsideOfBlock(BB))
return ~0U;
+ // Blocks with NoDuplicate are modelled as having infinite cost, so they
+ // are never duplicated.
+ if (const CallInst *CI = dyn_cast<CallInst>(I))
+ if (CI->cannotDuplicate() || CI->isConvergent())
+ return ~0U;
+
+ if (TTI->getUserCost(&*I, TargetTransformInfo::TCK_SizeAndLatency)
+ == TargetTransformInfo::TCC_Free)
+ continue;
+
// All other instructions count for at least one unit.
++Size;
@@ -578,11 +576,7 @@ static unsigned getJumpThreadDuplicationCost(BasicBlock *BB,
// as having cost of 2 total, and if they are a vector intrinsic, we model
// them as having cost 1.
if (const CallInst *CI = dyn_cast<CallInst>(I)) {
- if (CI->cannotDuplicate() || CI->isConvergent())
- // Blocks with NoDuplicate are modelled as having infinite cost, so they
- // are never duplicated.
- return ~0U;
- else if (!isa<IntrinsicInst>(CI))
+ if (!isa<IntrinsicInst>(CI))
Size += 3;
else if (!CI->getType()->isVectorTy())
Size += 1;
@@ -2234,10 +2228,10 @@ bool JumpThreadingPass::maybethreadThroughTwoBasicBlocks(BasicBlock *BB,
}
// Compute the cost of duplicating BB and PredBB.
- unsigned BBCost =
- getJumpThreadDuplicationCost(BB, BB->getTerminator(), BBDupThreshold);
+ unsigned BBCost = getJumpThreadDuplicationCost(
+ TTI, BB, BB->getTerminator(), BBDupThreshold);
unsigned PredBBCost = getJumpThreadDuplicationCost(
- PredBB, PredBB->getTerminator(), BBDupThreshold);
+ TTI, PredBB, PredBB->getTerminator(), BBDupThreshold);
// Give up if costs are too high. We need to check BBCost and PredBBCost
// individually before checking their sum because getJumpThreadDuplicationCost
@@ -2345,8 +2339,8 @@ bool JumpThreadingPass::tryThreadEdge(
return false;
}
- unsigned JumpThreadCost =
- getJumpThreadDuplicationCost(BB, BB->getTerminator(), BBDupThreshold);
+ unsigned JumpThreadCost = getJumpThreadDuplicationCost(
+ TTI, BB, BB->getTerminator(), BBDupThreshold);
if (JumpThreadCost > BBDupThreshold) {
LLVM_DEBUG(dbgs() << " Not threading BB '" << BB->getName()
<< "' - Cost is too high: " << JumpThreadCost << "\n");
@@ -2614,8 +2608,8 @@ bool JumpThreadingPass::duplicateCondBranchOnPHIIntoPred(
return false;
}
- unsigned DuplicationCost =
- getJumpThreadDuplicationCost(BB, BB->getTerminator(), BBDupThreshold);
+ unsigned DuplicationCost = getJumpThreadDuplicationCost(
+ TTI, BB, BB->getTerminator(), BBDupThreshold);
if (DuplicationCost > BBDupThreshold) {
LLVM_DEBUG(dbgs() << " Not duplicating BB '" << BB->getName()
<< "' - Cost is too high: " << DuplicationCost << "\n");
@@ -3031,7 +3025,8 @@ bool JumpThreadingPass::threadGuard(BasicBlock *BB, IntrinsicInst *Guard,
ValueToValueMapTy UnguardedMapping, GuardedMapping;
Instruction *AfterGuard = Guard->getNextNode();
- unsigned Cost = getJumpThreadDuplicationCost(BB, AfterGuard, BBDupThreshold);
+ unsigned Cost =
+ getJumpThreadDuplicationCost(TTI, BB, AfterGuard, BBDupThreshold);
if (Cost > BBDupThreshold)
return false;
// Duplicate all instructions before the guard and the guard itself to the
diff --git a/llvm/test/Transforms/JumpThreading/free_instructions.ll b/llvm/test/Transforms/JumpThreading/free_instructions.ll
index f768ec9967795..76392af77d33d 100644
--- a/llvm/test/Transforms/JumpThreading/free_instructions.ll
+++ b/llvm/test/Transforms/JumpThreading/free_instructions.ll
@@ -5,26 +5,28 @@
; the jump threading threshold, as everything else are free instructions.
define i32 @free_instructions(i1 %c, i32* %p) {
; CHECK-LABEL: @free_instructions(
-; CHECK-NEXT: br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
-; CHECK: if:
+; CHECK-NEXT: br i1 [[C:%.*]], label [[IF2:%.*]], label [[ELSE2:%.*]]
+; CHECK: if2:
; CHECK-NEXT: store i32 -1, i32* [[P:%.*]], align 4
-; CHECK-NEXT: br label [[JOIN:%.*]]
-; CHECK: else:
-; CHECK-NEXT: store i32 -2, i32* [[P]], align 4
-; CHECK-NEXT: br label [[JOIN]]
-; CHECK: join:
; CHECK-NEXT: call void @llvm.experimental.noalias.scope.decl(metadata [[META0:![0-9]+]])
; CHECK-NEXT: store i32 1, i32* [[P]], align 4, !noalias !0
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(i32* [[P]], i64 32) ]
; CHECK-NEXT: store i32 2, i32* [[P]], align 4
+; CHECK-NEXT: [[P21:%.*]] = bitcast i32* [[P]] to i8*
+; CHECK-NEXT: [[P32:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* [[P21]])
+; CHECK-NEXT: [[P43:%.*]] = bitcast i8* [[P32]] to i32*
+; CHECK-NEXT: store i32 3, i32* [[P43]], align 4, !invariant.group !3
+; CHECK-NEXT: ret i32 0
+; CHECK: else2:
+; CHECK-NEXT: store i32 -2, i32* [[P]], align 4
+; CHECK-NEXT: call void @llvm.experimental.noalias.scope.decl(metadata [[META4:![0-9]+]])
+; CHECK-NEXT: store i32 1, i32* [[P]], align 4, !noalias !4
+; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(i32* [[P]], i64 32) ]
+; CHECK-NEXT: store i32 2, i32* [[P]], align 4
; CHECK-NEXT: [[P2:%.*]] = bitcast i32* [[P]] to i8*
; CHECK-NEXT: [[P3:%.*]] = call i8* @llvm.launder.invariant.group.p0i8(i8* [[P2]])
; CHECK-NEXT: [[P4:%.*]] = bitcast i8* [[P3]] to i32*
; CHECK-NEXT: store i32 3, i32* [[P4]], align 4, !invariant.group !3
-; CHECK-NEXT: br i1 [[C]], label [[IF2:%.*]], label [[ELSE2:%.*]]
-; CHECK: if2:
-; CHECK-NEXT: ret i32 0
-; CHECK: else2:
; CHECK-NEXT: ret i32 1
;
br i1 %c, label %if, label %else
diff --git a/llvm/test/Transforms/PhaseOrdering/inlining-alignment-assumptions.ll b/llvm/test/Transforms/PhaseOrdering/inlining-alignment-assumptions.ll
index 57014e856a090..f764a59dd8a2f 100644
--- a/llvm/test/Transforms/PhaseOrdering/inlining-alignment-assumptions.ll
+++ b/llvm/test/Transforms/PhaseOrdering/inlining-alignment-assumptions.ll
@@ -32,13 +32,10 @@ define void @caller1(i1 %c, i64* align 1 %ptr) {
; ASSUMPTIONS-OFF-NEXT: br label [[COMMON_RET]]
;
; ASSUMPTIONS-ON-LABEL: @caller1(
-; ASSUMPTIONS-ON-NEXT: br i1 [[C:%.*]], label [[COMMON_RET:%.*]], label [[FALSE1:%.*]]
-; ASSUMPTIONS-ON: false1:
-; ASSUMPTIONS-ON-NEXT: store volatile i64 1, i64* [[PTR:%.*]], align 4
-; ASSUMPTIONS-ON-NEXT: br label [[COMMON_RET]]
+; ASSUMPTIONS-ON-NEXT: br i1 [[C:%.*]], label [[COMMON_RET:%.*]], label [[FALSE2:%.*]]
; ASSUMPTIONS-ON: common.ret:
-; ASSUMPTIONS-ON-NEXT: [[DOTSINK:%.*]] = phi i64 [ 3, [[FALSE1]] ], [ 2, [[TMP0:%.*]] ]
-; ASSUMPTIONS-ON-NEXT: call void @llvm.assume(i1 true) [ "align"(i64* [[PTR]], i64 8) ]
+; ASSUMPTIONS-ON-NEXT: [[DOTSINK:%.*]] = phi i64 [ 3, [[FALSE2]] ], [ 2, [[TMP0:%.*]] ]
+; ASSUMPTIONS-ON-NEXT: call void @llvm.assume(i1 true) [ "align"(i64* [[PTR:%.*]], i64 8) ]
; ASSUMPTIONS-ON-NEXT: store volatile i64 0, i64* [[PTR]], align 8
; ASSUMPTIONS-ON-NEXT: store volatile i64 -1, i64* [[PTR]], align 8
; ASSUMPTIONS-ON-NEXT: store volatile i64 -1, i64* [[PTR]], align 8
@@ -47,6 +44,9 @@ define void @caller1(i1 %c, i64* align 1 %ptr) {
; ASSUMPTIONS-ON-NEXT: store volatile i64 -1, i64* [[PTR]], align 8
; ASSUMPTIONS-ON-NEXT: store volatile i64 [[DOTSINK]], i64* [[PTR]], align 8
; ASSUMPTIONS-ON-NEXT: ret void
+; ASSUMPTIONS-ON: false2:
+; ASSUMPTIONS-ON-NEXT: store volatile i64 1, i64* [[PTR]], align 4
+; ASSUMPTIONS-ON-NEXT: br label [[COMMON_RET]]
;
br i1 %c, label %true1, label %false1
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