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Detect when a value is undefined on an edge to a landing pad.

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Consider this code:

int h() {
  int x;
  try {
    x = f();
    g();
  } catch (...) {
    return x+1;
  }
  return x;
}

The variable x is undefined on the first edge to the landing pad, but it
has the f() return value on the second edge to the landing pad.

SplitAnalysis::getLastSplitPoint() would assume that the return value
from f() was live into the landing pad when f() throws, which is of
course impossible.

Detect these cases, and treat them as if the landing pad wasn't there.
This allows spill code to be inserted after the function call to f().

<rdar://problem/10664933>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147912 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-01-11 02:07:05 +00:00
parent 74c4f97a46
commit 2aad2f6e60
3 changed files with 180 additions and 4 deletions
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6
include/llvm/CodeGen/SlotIndexes.h
View File

@ -208,6 +208,12 @@ namespace llvm {
return A.lie.getPointer() == B.lie.getPointer();
}
/// isEarlierInstr - Return true if A refers to an instruction earlier than
/// B. This is equivalent to A < B && !isSameInstr(A, B).
static bool isEarlierInstr(SlotIndex A, SlotIndex B) {
return A.entry().getIndex() < B.entry().getIndex();
}
/// Return the distance from this index to the given one.
int distance(SlotIndex other) const {
return other.getIndex() - getIndex();

23
lib/CodeGen/SplitKit.cpp
View File

@ -62,13 +62,14 @@ SlotIndex SplitAnalysis::computeLastSplitPoint(unsigned Num) {
const MachineBasicBlock *MBB = MF.getBlockNumbered(Num);
const MachineBasicBlock *LPad = MBB->getLandingPadSuccessor();
std::pair<SlotIndex, SlotIndex> &LSP = LastSplitPoint[Num];
SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
// Compute split points on the first call. The pair is independent of the
// current live interval.
if (!LSP.first.isValid()) {
MachineBasicBlock::const_iterator FirstTerm = MBB->getFirstTerminator();
if (FirstTerm == MBB->end())
LSP.first = LIS.getMBBEndIdx(MBB);
LSP.first = MBBEnd;
else
LSP.first = LIS.getInstructionIndex(FirstTerm);
@ -89,10 +90,24 @@ SlotIndex SplitAnalysis::computeLastSplitPoint(unsigned Num) {
// If CurLI is live into a landing pad successor, move the last split point
// back to the call that may throw.
if (LPad && LSP.second.isValid() && LIS.isLiveInToMBB(*CurLI, LPad))
return LSP.second;
else
if (!LPad || !LSP.second || !LIS.isLiveInToMBB(*CurLI, LPad))
return LSP.first;
// Find the value leaving MBB.
const VNInfo *VNI = CurLI->getVNInfoBefore(MBBEnd);
if (!VNI)
return LSP.first;
// If the value leaving MBB was defined after the call in MBB, it can't
// really be live-in to the landing pad. This can happen if the landing pad
// has a PHI, and this register is undef on the exceptional edge.
// <rdar://problem/10664933>
if (!SlotIndex::isEarlierInstr(VNI->def, LSP.second) && VNI->def < MBBEnd)
return LSP.first;
// Value is properly live-in to the landing pad.
// Only allow splits before the call.
return LSP.second;
}
MachineBasicBlock::iterator

155
test/CodeGen/X86/2012-01-10-UndefExceptionEdge.ll Normal file
View File

@ -0,0 +1,155 @@
; RUN: llc < %s -disable-fp-elim
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32-S128"
target triple = "i386-apple-macosx10.7"
; This test case has a landing pad with two predecessors, and a variable that
; is undef on the first edge while carrying the first function return value on
; the second edge.
;
; Live range splitting tries to isolate the block containing the first function
; call, and it is important that the last split point is after the function call
; so the return value can spill.
;
; <rdar://problem/10664933>
@Exception = external unnamed_addr constant { i8*, i8* }
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind
define void @f(i32* nocapture %arg, i32* nocapture %arg1, i32* nocapture %arg2, i32* nocapture %arg3, i32 %arg4, i32 %arg5) optsize ssp {
bb:
br i1 undef, label %bb6, label %bb7
bb6: ; preds = %bb
%tmp = select i1 false, i32 0, i32 undef
br label %bb7
bb7: ; preds = %bb6, %bb
%tmp8 = phi i32 [ %tmp, %bb6 ], [ 0, %bb ]
%tmp9 = shl i32 %tmp8, 2
%tmp10 = invoke noalias i8* @_Znam(i32 undef) optsize
to label %bb11 unwind label %bb20
bb11: ; preds = %bb7
%tmp12 = ptrtoint i8* %tmp10 to i32
%tmp13 = bitcast i8* %tmp10 to i32*
%tmp14 = shl i32 %tmp8, 2
%tmp15 = getelementptr i32* %tmp13, i32 undef
%tmp16 = getelementptr i32* %tmp13, i32 undef
%tmp17 = zext i32 %tmp9 to i64
%tmp18 = add i64 %tmp17, -1
%tmp19 = icmp ugt i64 %tmp18, 4294967295
br i1 %tmp19, label %bb29, label %bb31
bb20: ; preds = %bb43, %bb41, %bb29, %bb7
%tmp21 = phi i32 [ undef, %bb7 ], [ %tmp12, %bb43 ], [ %tmp12, %bb29 ], [ %tmp12, %bb41 ]
%tmp22 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
catch i8* bitcast ({ i8*, i8* }* @Exception to i8*)
br i1 undef, label %bb23, label %bb69
bb23: ; preds = %bb38, %bb20
%tmp24 = phi i32 [ %tmp12, %bb38 ], [ %tmp21, %bb20 ]
%tmp25 = icmp eq i32 %tmp24, 0
br i1 %tmp25, label %bb28, label %bb26
bb26: ; preds = %bb23
%tmp27 = inttoptr i32 %tmp24 to i8*
br label %bb28
bb28: ; preds = %bb26, %bb23
ret void
bb29: ; preds = %bb11
invoke void @OnOverFlow() optsize
to label %bb30 unwind label %bb20
bb30: ; preds = %bb29
unreachable
bb31: ; preds = %bb11
%tmp32 = bitcast i32* %tmp15 to i8*
%tmp33 = zext i32 %tmp8 to i64
%tmp34 = add i64 %tmp33, -1
%tmp35 = icmp ugt i64 %tmp34, 4294967295
%tmp36 = icmp sgt i32 %tmp8, 0
%tmp37 = add i32 %tmp9, -4
br label %bb38
bb38: ; preds = %bb67, %bb31
%tmp39 = phi i32 [ %tmp68, %bb67 ], [ undef, %bb31 ]
%tmp40 = icmp sgt i32 %tmp39, undef
br i1 %tmp40, label %bb41, label %bb23
bb41: ; preds = %bb38
invoke void @Pjii(i32* %tmp16, i32 0, i32 %tmp8) optsize
to label %bb42 unwind label %bb20
bb42: ; preds = %bb41
tail call void @llvm.memset.p0i8.i32(i8* %tmp32, i8 0, i32 %tmp9, i32 1, i1 false) nounwind
br i1 %tmp35, label %bb43, label %bb45
bb43: ; preds = %bb42
invoke void @OnOverFlow() optsize
to label %bb44 unwind label %bb20
bb44: ; preds = %bb43
unreachable
bb45: ; preds = %bb57, %bb42
%tmp46 = phi i32 [ %tmp58, %bb57 ], [ 255, %bb42 ]
%tmp47 = icmp slt i32 undef, 0
br i1 %tmp47, label %bb48, label %bb59
bb48: ; preds = %bb45
tail call void @llvm.memset.p0i8.i32(i8* %tmp32, i8 0, i32 %tmp9, i32 1, i1 false) nounwind
br i1 %tmp36, label %bb49, label %bb57
bb49: ; preds = %bb49, %bb48
%tmp50 = phi i32 [ %tmp55, %bb49 ], [ 0, %bb48 ]
%tmp51 = add i32 %tmp50, undef
%tmp52 = add i32 %tmp50, undef
%tmp53 = getelementptr i32* %tmp13, i32 %tmp52
%tmp54 = load i32* %tmp53, align 4, !tbaa !0
%tmp55 = add i32 %tmp50, 1
%tmp56 = icmp eq i32 %tmp55, %tmp8
br i1 %tmp56, label %bb57, label %bb49
bb57: ; preds = %bb49, %bb48
%tmp58 = add i32 %tmp46, -1
br label %bb45
bb59: ; preds = %bb45
%tmp60 = ashr i32 %tmp46, 31
tail call void @llvm.memset.p0i8.i32(i8* null, i8 0, i32 %tmp37, i32 1, i1 false) nounwind
br i1 %tmp36, label %bb61, label %bb67
bb61: ; preds = %bb61, %bb59
%tmp62 = phi i32 [ %tmp65, %bb61 ], [ 0, %bb59 ]
%tmp63 = add i32 %tmp62, %tmp14
%tmp64 = getelementptr i32* %tmp13, i32 %tmp63
store i32 0, i32* %tmp64, align 4, !tbaa !0
%tmp65 = add i32 %tmp62, 1
%tmp66 = icmp eq i32 %tmp65, %tmp8
br i1 %tmp66, label %bb67, label %bb61
bb67: ; preds = %bb61, %bb59
%tmp68 = add i32 %tmp39, -1
br label %bb38
bb69: ; preds = %bb20
resume { i8*, i32 } %tmp22
}
declare i32 @__gxx_personality_v0(...)
declare noalias i8* @_Znam(i32) optsize
declare void @Pjii(i32*, i32, i32) optsize
declare i32 @llvm.eh.typeid.for(i8*) nounwind readnone
declare void @OnOverFlow() noreturn optsize ssp align 2
!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA", null}