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[IPSCCP] Move callsite check to the beginning of the loop.

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We have some code marks instructions with struct operands as overdefined,
but if the instruction is a call to a function with tracked arguments,
this breaks the assumption that the lattice values of all call sites
are not overdefined and will be replaced by a constant.

This also re-adds the assertion from D65222, with additionally skipping
non-callsite uses. This patch should address the cases reported in which
the assertion fired.

Fixes PR42738.

Reviewers: efriedma, davide

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D65439

llvm-svn: 367430
This commit is contained in:
Florian Hahn 2019-07-31 12:57:04 +00:00
parent 7a52a1bfe8
commit 8d80009f96
3 changed files with 122 additions and 15 deletions
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54
lib/Transforms/Scalar/SCCP.cpp
View File

@ -1465,7 +1465,24 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
}
LatticeVal &LV = getValueState(&I);
if (!LV.isUnknown()) continue;
if (!LV.isUnknown())
continue;
// There are two reasons a call can have an undef result
// 1. It could be tracked.
// 2. It could be constant-foldable.
// Because of the way we solve return values, tracked calls must
// never be marked overdefined in ResolvedUndefsIn.
if (CallSite CS = CallSite(&I)) {
if (Function *F = CS.getCalledFunction())
if (TrackedRetVals.count(F))
continue;
// If the call is constant-foldable, we mark it overdefined because
// we do not know what return values are valid.
markOverdefined(&I);
return true;
}
// extractvalue is safe; check here because the argument is a struct.
if (isa<ExtractValueInst>(I))
@ -1638,19 +1655,7 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
case Instruction::Call:
case Instruction::Invoke:
case Instruction::CallBr:
// There are two reasons a call can have an undef result
// 1. It could be tracked.
// 2. It could be constant-foldable.
// Because of the way we solve return values, tracked calls must
// never be marked overdefined in ResolvedUndefsIn.
if (Function *F = CallSite(&I).getCalledFunction())
if (TrackedRetVals.count(F))
break;
// If the call is constant-foldable, we mark it overdefined because
// we do not know what return values are valid.
markOverdefined(&I);
return true;
llvm_unreachable("Call-like instructions should have be handled early");
default:
// If we don't know what should happen here, conservatively mark it
// overdefined.
@ -1924,6 +1929,27 @@ static void findReturnsToZap(Function &F,
return;
}
assert(
all_of(F.users(),
[&Solver](User *U) {
if (isa<Instruction>(U) &&
!Solver.isBlockExecutable(cast<Instruction>(U)->getParent()))
return true;
// Non-callsite uses are not impacted by zapping. Also, constant
// uses (like blockaddresses) could stuck around, without being
// used in the underlying IR, meaning we do not have lattice
// values for them.
if (!CallSite(U))
return true;
if (U->getType()->isStructTy()) {
return all_of(
Solver.getStructLatticeValueFor(U),
[](const LatticeVal &LV) { return !LV.isOverdefined(); });
}
return !Solver.getLatticeValueFor(U).isOverdefined();
}) &&
"We can only zap functions where all live users have a concrete value");
for (BasicBlock &BB : F) {
if (CallInst *CI = BB.getTerminatingMustTailCall()) {
LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "

34
test/Transforms/SCCP/indirectbr.ll
View File

@ -1,4 +1,4 @@
; RUN: opt -S -sccp < %s | FileCheck %s
; RUN: opt -S -ipsccp < %s | FileCheck %s
declare void @BB0_f()
declare void @BB1_f()
@ -74,3 +74,35 @@ BB1:
}
; CHECK-LABEL: define internal i32 @indbrtest5(
; CHECK: ret i32 undef
define internal i32 @indbrtest5(i1 %c) {
entry:
br i1 %c, label %bb1, label %bb2
bb1:
br label %branch.block
bb2:
br label %branch.block
branch.block:
%addr = phi i8* [blockaddress(@indbrtest5, %target1), %bb1], [blockaddress(@indbrtest5, %target2), %bb2]
indirectbr i8* %addr, [label %target1, label %target2]
target1:
br label %target2
target2:
ret i32 10
}
define i32 @indbrtest5_callee(i1 %c) {
; CHECK-LABEL: define i32 @indbrtest5_callee(
; CHECK-NEXT: %r = call i32 @indbrtest5(i1 %c)
; CHECK-NEXT: ret i32 10
%r = call i32 @indbrtest5(i1 %c)
ret i32 %r
}

49
test/Transforms/SCCP/struct-arg-resolve-undefs.ll Normal file
View File

@ -0,0 +1,49 @@
; RUN: opt -ipsccp -S %s | FileCheck %s
%struct.S = type { i32 }
define void @main() {
; CHECK-LABEL: void @main() {
; CHECK-NEXT: %r = call i32 @f(%struct.S { i32 100 })
; CHECK-NEXT: call void @do_report(i32 123)
%r = call i32 @f(%struct.S { i32 100 })
call void @do_report(i32 %r)
ret void
}
declare void @do_report(i32)
define internal i32 @f(%struct.S %s.coerce) {
; CHECK-LABEL: define internal i32 @f(%struct.S %s.coerce)
; CHECK-LABEL: entry:
; CHECK-NEXT: %call = call i8 @lsh(i8 1, i32 100)
; CHECK-LABEL: if.end:
; CHECK-NEXT: ret i32 undef
entry:
%ev = extractvalue %struct.S %s.coerce, 0
%call = call i8 @lsh(i8 1, i32 %ev)
%tobool = icmp ne i8 %call, 0
br i1 %tobool, label %for.cond, label %if.end
for.cond: ; preds = %for.cond, %if.then
%i.0 = phi i32 [ 0, %entry], [ %inc, %for.cond ]
%cmp = icmp slt i32 %i.0, 1
%inc = add nsw i32 %i.0, 1
br i1 %cmp, label %for.cond, label %if.end
if.end: ; preds = %for.cond, %entry
ret i32 123
}
define internal i8 @lsh(i8 %l, i32 %r) {
entry:
%conv = sext i8 %l to i32
%cmp = icmp slt i32 %conv, 0
%shr = ashr i32 127, %r
%cmp4 = icmp sgt i32 %conv, %shr
%or.cond13 = or i1 %cmp, %cmp4
%cond = select i1 %or.cond13, i32 %conv, i32 0
%conv7 = trunc i32 %cond to i8
ret i8 %conv7
}