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[SwiftError] Use IMPLICIT_DEF as a definition for unreachable VReg uses

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SwiftErrorValueTracking creates vregs at swifterror use sites and then
connects it with appropriate definitions after instruction selection.
To propagate swifterror values SwiftErrorValueTracking::propagateVRegs
iterates over basic blocks in RPO, but some vregs previously created
at use sites may be located in blocks that became unreachable after
instruction selection. Because of that there will no definition for
such vregs and that may cause issues down the pipeline.

To ensure that all vregs created by the SwiftErrorValueTracking will
be defined propagateVRegs was updated to insert IMPLICIT_DEF at the
beginning of unreachable blocks containing swifterror uses.

Related issue: https://github.com/llvm/llvm-project/issues/59751

Reviewed By: compnerd

Differential Revision: https://reviews.llvm.org/D141053
This commit is contained in:
Filipp Zhinkin 2023-01-05 18:57:42 +04:00
parent 1b95661616
commit 08d0b558f5
2 changed files with 58 additions and 0 deletions
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19
llvm/lib/CodeGen/SwiftErrorValueTracking.cpp
View File

@ -253,6 +253,25 @@ void SwiftErrorValueTracking::propagateVRegs() {
setCurrentVReg(MBB, SwiftErrorVal, PHIVReg);
}
}
// Create implicit defs for upward uses from unreachable blocks
MachineRegisterInfo &MRI = MF->getRegInfo();
for (const auto &Use : VRegUpwardsUse) {
const MachineBasicBlock *UseBB = Use.first.first;
Register VReg = Use.second;
if (!MRI.def_begin(VReg).atEnd())
continue;
#ifdef EXPENSIVE_CHECKS
assert(std::find(RPOT.begin(), RPOT.end(), UseBB) == RPOT.end() &&
"Reachable block has VReg upward use without definition.");
#endif
MachineBasicBlock *UseBBMut = MF->getBlockNumbered(UseBB->getNumber());
BuildMI(*UseBBMut, UseBBMut->getFirstNonPHI(), DebugLoc(),
TII->get(TargetOpcode::IMPLICIT_DEF), VReg);
}
}
void SwiftErrorValueTracking::preassignVRegs(

39
llvm/test/CodeGen/AArch64/swift-error-unreachable-use.ll Normal file
View File

@ -0,0 +1,39 @@
; RUN: llc -mtriple aarch64-unknown-windows-msvc %s -filetype asm -o - | FileCheck %s
; RUN: llc -mtriple aarch64-unknown-linux-gnu %s -filetype asm -o - | FileCheck %s
; RUN: llc -mtriple aarch64-apple-macosx %s -filetype asm -o - | FileCheck %s
; Regression test for https://github.com/llvm/llvm-project/issues/59751
define void @"func"(i32** swifterror %0) #0 {
; CHECK-LABEL: func:
; CHECK: {{.*}}%bb.0:
; CHECK-NEXT: b {{\.?}}LBB0_2
; CHECK-NEXT: {{\.?}}LBB0_1:{{.*}}%thirtythree
; CHECK-NEXT: {{.*}}=>This Inner Loop Header: Depth=1
; CHECK-NEXT: b {{\.?}}LBB0_1
; CHECK-NEXT: {{\.?}}LBB0_2:{{.*}}%thirtyeight
; CHECK-NEXT: b {{\.?}}LBB0_3
; CHECK-NEXT: {{\.?}}LBB0_3:{{.*}}%thirtythree.preheader
; CHECK-NEXT: b {{\.?}}LBB0_1
br label %thirtyeight
five:
br label %UelOc2l.exit
common.ret:
ret void
UelOc2l.exit:
%a = getelementptr inbounds [754 x i8*], [754 x i8*]* undef, i32 undef, i32 undef
%b = load i8*, i8** %a, align 8
%c = bitcast i8* %b to void ()*
call void %c()
br label %common.ret
thirtythree:
br i1 false, label %UelOc2l.exit, label %thirtythree
thirtyeight:
br i1 undef, label %thirtyeight, label %thirtythree
}
attributes #0 = { noinline optnone }