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[Statepoints] Disable VReg lowering for values used on exception path…
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… of invoke.

Currently we lower invokes the same way as usual calls, e.g.:

V1 = STATEPOINT ... V (tied-def 0)

But this is incorrect is V1 is used on exceptional path.
By LLVM rules V1 neither dominates its uses in landing pad, nor
its live range is live on entry to landing pad. So compiler is
allowed to do various weird transformations like splitting live
range after statepoint and use split LR in catch block.

Until (and if) we find better solution to this problem, let's
use old lowering (spilling) for those values which are used on
exceptional path and allow VReg lowering for values used only
on normal path.

Differential Revision: https://reviews.llvm.org/D93449
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@dantrushin
dantrushin committed Dec 21, 2020
1 parent b2ba686 commit 6f45049
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Showing 2 changed files with 47 additions and 22 deletions.
24 changes: 23 additions & 1 deletion llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -546,6 +546,18 @@ lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
// Decide which deriver pointers will go on VRegs
unsigned MaxVRegPtrs = MaxRegistersForGCPointers.getValue();

// Pointers used on exceptional path of invoke statepoint.
// We cannot assing them to VRegs.
SmallSet<SDValue, 8> LPadPointers;
if (auto *StInvoke = dyn_cast_or_null<InvokeInst>(SI.StatepointInstr)) {
LandingPadInst *LPI = StInvoke->getLandingPadInst();
for (auto *Relocate : SI.GCRelocates)
if (Relocate->getOperand(0) == LPI) {
LPadPointers.insert(Builder.getValue(Relocate->getBasePtr()));
LPadPointers.insert(Builder.getValue(Relocate->getDerivedPtr()));
}
}

LLVM_DEBUG(dbgs() << "Deciding how to lower GC Pointers:\n");

// List of unique lowered GC Pointer values.
Expand All @@ -555,6 +567,14 @@ lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,

unsigned CurNumVRegs = 0;

auto canPassGCPtrOnVReg = [&](SDValue SD) {
if (SD.getValueType().isVector())
return false;
if (LPadPointers.count(SD))
return false;
return !willLowerDirectly(SD);
};

auto processGCPtr = [&](const Value *V) {
SDValue PtrSD = Builder.getValue(V);
if (!LoweredGCPtrs.insert(PtrSD))
Expand All @@ -564,7 +584,9 @@ lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
assert(!LowerAsVReg.count(PtrSD) && "must not have been seen");
if (LowerAsVReg.size() == MaxVRegPtrs)
return;
if (willLowerDirectly(PtrSD) || V->getType()->isVectorTy()) {
assert(V->getType()->isVectorTy() == PtrSD.getValueType().isVector() &&
"IR and SD types disagree");
if (!canPassGCPtrOnVReg(PtrSD)) {
LLVM_DEBUG(dbgs() << "direct/spill "; PtrSD.dump(&Builder.DAG));
return;
}
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45 changes: 24 additions & 21 deletions llvm/test/CodeGen/X86/statepoint-vreg-invoke.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -10,14 +10,16 @@ declare dso_local i32* @personality_function()
define i64 addrspace(1)* @test_basic_invoke(i64 addrspace(1)* %obj, i64 addrspace(1)* %obj1)
; CHECK-LABEL: name: test_basic_invoke
; CHECK: bb.0.entry:
; CHECK: renamable $r14, renamable $rbx = STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 5, 2, 0, 2, -1, 2, 0, 2, 0, 2, 0, 2, 2, killed renamable $r14(tied-def 0), killed renamable $rbx(tied-def 1), 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp
; CHECK: MOV64mr %stack.1, 1, $noreg, 0, $noreg, renamable $rdi :: (store 8 into %stack.1)
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, killed renamable $rsi :: (store 8 into %stack.0)
; CHECK: STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 5, 2, 0, 2, -1, 2, 0, 2, 0, 2, 0, 2, 2, 1, 8, %stack.0, 0, 1, 8, %stack.1, 0, 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0), (volatile load store 8 on %stack.1)
; CHECK: JMP_1 %bb.1
; CHECK: bb.1.safepoint_normal_dest:
; CHECK: renamable $rax = MOV64rm %stack.1, 1, $noreg, 0, $noreg :: (load 8 from %stack.1)
; CHECK: bb.2.normal_return:
; CHECK: $rax = COPY killed renamable $rbx
; CHECK: RET 0, $rax
; CHECK: bb.3.exceptional_return (landing-pad):
; CHECK: $rax = COPY killed renamable $r14
; CHECK: renamable $rax = MOV64rm %stack.0, 1, $noreg, 0, $noreg :: (load 8 from %stack.0)
; CHECK: RET 0, $rax
gc "statepoint-example" personality i32* ()* @"personality_function" {
entry:
Expand All @@ -43,35 +45,37 @@ exceptional_return:
define i64 addrspace(1)* @test_invoke_same_val(i1 %cond, i64 addrspace(1)* %val1, i64 addrspace(1)* %val2, i64 addrspace(1)* %val3)
; CHECK-LABEL: name: test_invoke_same_val
; CHECK: bb.0.entry:
; CHECK: renamable $r15 = COPY $rcx
; CHECK: renamable $rbx = COPY $rdx
; CHECK: renamable $rbp = COPY $rsi
; CHECK: renamable $rbx = COPY $rcx
; CHECK: renamable $rbp = COPY $rdx
; CHECK: renamable $r14d = COPY $edi
; CHECK: TEST8ri renamable $r14b, 1, implicit-def $eflags
; CHECK: JCC_1 %bb.3, 4, implicit killed $eflags
; CHECK: JMP_1 %bb.1
; CHECK: bb.1.left:
; CHECK: $rdi = COPY renamable $rbp
; CHECK: renamable $rbx, renamable $rbp = STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 0, 2, 2, killed renamable $rbx(tied-def 0), killed renamable $rbp(tied-def 1), 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, renamable $rsi :: (store 8 into %stack.0)
; CHECK: $rdi = COPY killed renamable $rsi
; CHECK: renamable $rbp = STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 0, 2, 2, killed renamable $rbp(tied-def 0), 1, 8, %stack.0, 0, 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0)
; CHECK: JMP_1 %bb.2
; CHECK: bb.2.left.relocs:
; CHECK: renamable $rbx = MOV64rm %stack.0, 1, $noreg, 0, $noreg :: (load 8 from %stack.0)
; CHECK: JMP_1 %bb.5
; CHECK: bb.3.right:
; CHECK: $rdi = COPY killed renamable $rbp
; CHECK: renamable $r15, renamable $rbx = STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 0, 2, 2, killed renamable $r15(tied-def 0), killed renamable $rbx(tied-def 1), 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, killed renamable $rbp :: (store 8 into %stack.0)
; CHECK: $rdi = COPY killed renamable $rsi
; CHECK: renamable $rbx = STATEPOINT 0, 0, 1, @some_call, $rdi, 2, 0, 2, 0, 2, 0, 2, 2, killed renamable $rbx(tied-def 0), 1, 8, %stack.0, 0, 2, 0, 2, 2, 0, 0, 1, 1, csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0)
; CHECK: JMP_1 %bb.4
; CHECK: bb.4.right.relocs:
; CHECK: renamable $rbp = COPY killed renamable $r15
; CHECK: renamable $rbp = MOV64rm %stack.0, 1, $noreg, 0, $noreg :: (load 8 from %stack.0)
; CHECK: bb.5.normal_return:
; CHECK: TEST8ri renamable $r14b, 1, implicit-def $eflags, implicit killed $r14d
; CHECK: renamable $rbp = CMOV64rr killed renamable $rbp, killed renamable $rbx, 4, implicit killed $eflags
; CHECK: $rax = COPY killed renamable $rbp
; CHECK: renamable $rbx = CMOV64rr killed renamable $rbx, killed renamable $rbp, 4, implicit killed $eflags
; CHECK: $rax = COPY killed renamable $rbx
; CHECK: RET 0, $rax
; CHECK: bb.6.exceptional_return.left (landing-pad):
; CHECK: $rax = COPY killed renamable $rbp
; CHECK: renamable $rax = MOV64rm %stack.0, 1, $noreg, 0, $noreg :: (load 8 from %stack.0)
; CHECK: RET 0, $rax
; CHECK: bb.7.exceptional_return.right (landing-pad):
; CHECK: $rax = COPY killed renamable $rbx
; CHECK: renamable $rax = MOV64rm %stack.0, 1, $noreg, 0, $noreg :: (load 8 from %stack.0)
; CHECK: RET 0, $rax
gc "statepoint-example" personality i32* ()* @"personality_function" {
entry:
Expand Down Expand Up @@ -117,17 +121,16 @@ exceptional_return.right:
define void @test_duplicate_ir_values() gc "statepoint-example" personality i32* ()* @personality_function {
; CHECK-LABEL: name: test_duplicate_ir_values
; CHECK: bb.0.entry:
; CHECK: renamable $rbx = MOV64rm undef renamable $rax, 1, $noreg, 0, $noreg :: (load 8 from `i8 addrspace(1)* addrspace(1)* undef`, addrspace 1)
; CHECK: renamable $rbx = STATEPOINT 1, 16, 5, undef renamable $rax, undef $edi, undef $rsi, undef $edx, undef $ecx, undef $r8d, 2, 0, 2, 0, 2, 0, 2, 1, killed renamable $rbx(tied-def 0), 2, 0, 2, 1, 0, 0, csr_64, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax
; CHECK: renamable $rax = MOV64rm undef renamable $rax, 1, $noreg, 0, $noreg :: (load 8 from `i8 addrspace(1)* addrspace(1)* undef`, addrspace 1)
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, killed renamable $rax :: (store 8 into %stack.0)
; CHECK: STATEPOINT 1, 16, 5, undef renamable $rax, undef $edi, undef $rsi, undef $edx, undef $ecx, undef $r8d, 2, 0, 2, 0, 2, 0, 2, 1, 1, 8, %stack.0, 0, 2, 0, 2, 1, 0, 0, csr_64, implicit-def $rsp, implicit-def $ssp, implicit-def dead $eax :: (volatile load store 8 on %stack.0)
; CHECK: JMP_1 %bb.1
; CHECK: bb.1.normal_continue:
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, killed renamable $rbx :: (store 8 into %stack.0)
; CHECK: $edi = MOV32ri 10
; CHECK: STATEPOINT 2882400000, 0, 1, target-flags(x86-plt) @__llvm_deoptimize, killed $edi, 2, 0, 2, 2, 2, 2, 1, 8, %stack.0, 0, 1, 8, %stack.0, 0, 2, 0, 2, 0, 2, 0, csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0)
; CHECK: STATEPOINT 2882400000, 0, 1, target-flags(x86-plt) @__llvm_deoptimize, killed $edi, 2, 0, 2, 2, 2, 2, 1, 8, %stack.0, 0, 1, 8, %stack.0, 0, 2, 0, 2, 0, 2, 0, csr_64, implicit-def $rsp, implicit-def $ssp
; CHECK: bb.2.exceptional_return (landing-pad):
; CHECK: MOV64mr %stack.0, 1, $noreg, 0, $noreg, killed renamable $rbx :: (store 8 into %stack.0)
; CHECK: $edi = MOV32ri -271
; CHECK: STATEPOINT 2882400000, 0, 1, target-flags(x86-plt) @__llvm_deoptimize, killed $edi, 2, 0, 2, 0, 2, 1, 1, 8, %stack.0, 0, 2, 0, 2, 0, 2, 0, csr_64, implicit-def $rsp, implicit-def $ssp :: (volatile load store 8 on %stack.0)
; CHECK: STATEPOINT 2882400000, 0, 1, target-flags(x86-plt) @__llvm_deoptimize, killed $edi, 2, 0, 2, 0, 2, 1, 1, 8, %stack.0, 0, 2, 0, 2, 0, 2, 0, csr_64, implicit-def $rsp, implicit-def $ssp
entry:
%val1 = load i8 addrspace(1)*, i8 addrspace(1)* addrspace(1)* undef, align 8
%val2 = load i8 addrspace(1)*, i8 addrspace(1)* addrspace(1)* undef, align 8
Expand Down

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