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[CVP] Use LVI to constant fold deopt operands 

Deopt operands are generally intended to record information about a site in code with minimal perturbation of the surrounding code. Idiomatically, they also tend to appear down rare paths. Putting these together, we have an obvious case for extending CVP w/deopt operand constant folding. Arguably, we should be doing this for all operands on all instructions, but that's definitely a much larger and risky change.

Differential Revision: https://reviews.llvm.org/D55678

llvm-svn: 351774
This commit is contained in:
Philip Reames 2019-01-22 01:34:33 +00:00
parent 9846f5f792
commit 390c0e2f72
3 changed files with 35 additions and 9 deletions
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4
llvm/lib/Analysis/LazyValueInfo.cpp
View File

@ -823,7 +823,9 @@ void LazyValueInfoImpl::intersectAssumeOrGuardBlockValueConstantRange(
if (!GuardDecl || GuardDecl->use_empty())
return;
for (Instruction &I : make_range(BBI->getIterator().getReverse(),
if (BBI->getIterator() == BBI->getParent()->begin())
return;
for (Instruction &I : make_range(std::next(BBI->getIterator().getReverse()),
BBI->getParent()->rend())) {
Value *Cond = nullptr;
if (match(&I, m_Intrinsic<Intrinsic::experimental_guard>(m_Value(Cond))))

24
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
View File

@ -462,6 +462,30 @@ static bool processCallSite(CallSite CS, LazyValueInfo *LVI) {
}
}
// Deopt bundle operands are intended to capture state with minimal
// perturbance of the code otherwise. If we can find a constant value for
// any such operand and remove a use of the original value, that's
// desireable since it may allow further optimization of that value (e.g. via
// single use rules in instcombine). Since deopt uses tend to,
// idiomatically, appear along rare conditional paths, it's reasonable likely
// we may have a conditional fact with which LVI can fold.
if (auto DeoptBundle = CS.getOperandBundle(LLVMContext::OB_deopt)) {
bool Progress = false;
for (const Use &ConstU : DeoptBundle->Inputs) {
Use &U = const_cast<Use&>(ConstU);
Value *V = U.get();
if (V->getType()->isVectorTy()) continue;
if (isa<Constant>(V)) continue;
Constant *C = LVI->getConstant(V, CS.getParent(), CS.getInstruction());
if (!C) continue;
U.set(C);
Progress = true;
}
if (Progress)
return true;
}
for (Value *V : CS.args()) {
PointerType *Type = dyn_cast<PointerType>(V->getType());
// Try to mark pointer typed parameters as non-null. We skip the

16
llvm/test/Transforms/CorrelatedValuePropagation/deopt.ll
View File

@ -11,7 +11,7 @@ define void @test1(i1 %c, i1 %c2) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEL2]], 0
; CHECK-NEXT: br i1 [[CMP]], label [[TAKEN:%.*]], label [[UNTAKEN:%.*]]
; CHECK: taken:
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 1) ]
; CHECK-NEXT: ret void
; CHECK: untaken:
; CHECK-NEXT: ret void
@ -37,7 +37,7 @@ define void @test1_assume(i1 %c, i1 %c2) {
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[C2:%.*]], i64 [[SEL]], i64 0
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEL2]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP]])
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 1) ]
; CHECK-NEXT: ret void
;
%sel = select i1 %c, i64 -1, i64 1
@ -55,7 +55,7 @@ define void @test1_guard(i1 %c, i1 %c2) {
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[C2:%.*]], i64 [[SEL]], i64 0
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEL2]], 0
; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 [[CMP]]) [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 1) ]
; CHECK-NEXT: ret void
;
%sel = select i1 %c, i64 -1, i64 1
@ -76,7 +76,7 @@ define void @test2(i1 %c, i1 %c2) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEL2]], 0
; CHECK-NEXT: br i1 [[CMP]], label [[TAKEN:%.*]], label [[UNTAKEN:%.*]]
; CHECK: taken:
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 1) ]
; CHECK-NEXT: ret void
; CHECK: untaken:
; CHECK-NEXT: ret void
@ -98,7 +98,7 @@ define void @test3(i1 %c, i1 %c2) {
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEL2]], 1
; CHECK-NEXT: br i1 [[CMP]], label [[TAKEN:%.*]], label [[UNTAKEN:%.*]]
; CHECK: taken:
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[SEL2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 2) ]
; CHECK-NEXT: ret void
; CHECK: untaken:
; CHECK-NEXT: ret void
@ -120,10 +120,10 @@ define void @test4(i1 %c, i1 %c2) {
; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[C2:%.*]], i64 0, i64 1
; CHECK-NEXT: [[ADD1:%.*]] = add i64 0, [[SEL]]
; CHECK-NEXT: [[ADD2:%.*]] = add i64 [[ADD1]], [[SEL2]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[ADD2]], 0
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[ADD2]], 1
; CHECK-NEXT: br i1 [[CMP]], label [[TAKEN:%.*]], label [[UNTAKEN:%.*]]
; CHECK: taken:
; CHECK-NEXT: call void @use() [ "deopt"(i64 [[ADD2]]) ]
; CHECK-NEXT: call void @use() [ "deopt"(i64 2) ]
; CHECK-NEXT: ret void
; CHECK: untaken:
; CHECK-NEXT: ret void
@ -132,7 +132,7 @@ define void @test4(i1 %c, i1 %c2) {
%sel2 = select i1 %c2, i64 0, i64 1
%add1 = add i64 0, %sel
%add2 = add i64 %add1, %sel2
%cmp = icmp sgt i64 %add2, 0
%cmp = icmp sgt i64 %add2, 1
br i1 %cmp, label %taken, label %untaken
taken:
call void @use() ["deopt" (i64 %add2)]