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Don't crash on extra evil irreducible control flow.

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When the CFG contains a loop with multiple entry blocks, the traces
computed by MachineTraceMetrics don't always have the same nice
properties. Loop back-edges are normally excluded from traces, but
MachineLoopInfo doesn't recognize loops with multiple entry blocks, so
those back-edges may be included.

Avoid asserting when that happens by adding an isEarlierInSameTrace()
function that accurately determines if a dominating block is part of the
same trace AND is above the currrent block in the trace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165434 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-10-08 22:06:44 +00:00
parent 8e635dbc78
commit 6be75ae196
3 changed files with 85 additions and 2 deletions
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4
lib/CodeGen/MachineTraceMetrics.cpp
View File

@ -677,7 +677,7 @@ computeCrossBlockCriticalPath(const TraceBlockInfo &TBI) {
const MachineInstr *DefMI = MTM.MRI->getVRegDef(LIR.Reg);
// Ignore dependencies outside the current trace.
const TraceBlockInfo &DefTBI = BlockInfo[DefMI->getParent()->getNumber()];
if (!DefTBI.hasValidDepth() || DefTBI.Head != TBI.Head)
if (!DefTBI.isEarlierInSameTrace(TBI))
continue;
unsigned Len = LIR.Height + Cycles[DefMI].Depth;
MaxLen = std::max(MaxLen, Len);
@ -740,7 +740,7 @@ computeInstrDepths(const MachineBasicBlock *MBB) {
const TraceBlockInfo&DepTBI =
BlockInfo[Dep.DefMI->getParent()->getNumber()];
// Ignore dependencies from outside the current trace.
if (!DepTBI.hasValidDepth() || DepTBI.Head != TBI.Head)
if (!DepTBI.isEarlierInSameTrace(TBI))
continue;
assert(DepTBI.HasValidInstrDepths && "Inconsistent dependency");
unsigned DepCycle = Cycles.lookup(Dep.DefMI).Depth;

8
lib/CodeGen/MachineTraceMetrics.h
View File

@ -165,6 +165,14 @@ public:
/// Invalidate height resources when a block below this one has changed.
void invalidateHeight() { InstrHeight = ~0u; HasValidInstrHeights = false; }
/// Determine if this block belongs to the same trace as TBI and comes
/// before it in the trace.
/// Also returns true when TBI == this.
bool isEarlierInSameTrace(const TraceBlockInfo &TBI) const {
return hasValidDepth() && TBI.hasValidDepth() &&
Head == TBI.Head && InstrDepth <= TBI.InstrDepth;
}
// Data-dependency-related information. Per-instruction depth and height
// are computed from data dependencies in the current trace, using
// itinerary data.

75
test/CodeGen/X86/early-ifcvt.ll
View File

@ -67,3 +67,78 @@ if.end41:
}
declare void @fprintf(...) nounwind
; CHECK: BZ2_decompress
; This test case contains irreducible control flow, so MachineLoopInfo doesn't
; recognize the cycle in the CFG. This would confuse MachineTraceMetrics.
define void @BZ2_decompress(i8* %s) nounwind ssp {
entry:
switch i32 undef, label %sw.default [
i32 39, label %if.end.sw.bb2050_crit_edge
i32 36, label %sw.bb1788
i32 37, label %if.end.sw.bb1855_crit_edge
i32 40, label %sw.bb2409
i32 38, label %sw.bb1983
i32 44, label %if.end.sw.bb3058_crit_edge
]
if.end.sw.bb3058_crit_edge: ; preds = %entry
br label %save_state_and_return
if.end.sw.bb1855_crit_edge: ; preds = %entry
br label %save_state_and_return
if.end.sw.bb2050_crit_edge: ; preds = %entry
br label %sw.bb2050
sw.bb1788: ; preds = %entry
br label %save_state_and_return
sw.bb1983: ; preds = %entry
br i1 undef, label %save_state_and_return, label %if.then1990
if.then1990: ; preds = %sw.bb1983
br label %while.body2038
while.body2038: ; preds = %sw.bb2050, %if.then1990
%groupPos.8 = phi i32 [ 0, %if.then1990 ], [ %groupPos.9, %sw.bb2050 ]
br i1 undef, label %save_state_and_return, label %if.end2042
if.end2042: ; preds = %while.body2038
br i1 undef, label %if.end2048, label %while.end2104
if.end2048: ; preds = %if.end2042
%bsLive2054.pre = getelementptr inbounds i8* %s, i32 8
br label %sw.bb2050
sw.bb2050: ; preds = %if.end2048, %if.end.sw.bb2050_crit_edge
%groupPos.9 = phi i32 [ 0, %if.end.sw.bb2050_crit_edge ], [ %groupPos.8, %if.end2048 ]
%and2064 = and i32 undef, 1
br label %while.body2038
while.end2104: ; preds = %if.end2042
br i1 undef, label %save_state_and_return, label %if.end2117
if.end2117: ; preds = %while.end2104
br i1 undef, label %while.body2161.lr.ph, label %while.body2145.lr.ph
while.body2145.lr.ph: ; preds = %if.end2117
br label %save_state_and_return
while.body2161.lr.ph: ; preds = %if.end2117
br label %save_state_and_return
sw.bb2409: ; preds = %entry
br label %save_state_and_return
sw.default: ; preds = %entry
call void @BZ2_bz__AssertH__fail() nounwind
br label %save_state_and_return
save_state_and_return:
%groupPos.14 = phi i32 [ 0, %sw.default ], [ %groupPos.8, %while.body2038 ], [ %groupPos.8, %while.end2104 ], [ 0, %if.end.sw.bb3058_crit_edge ], [ 0, %if.end.sw.bb1855_crit_edge ], [ %groupPos.8, %while.body2161.lr.ph ], [ %groupPos.8, %while.body2145.lr.ph ], [ 0, %sw.bb2409 ], [ 0, %sw.bb1788 ], [ 0, %sw.bb1983 ]
store i32 %groupPos.14, i32* undef, align 4
ret void
}
declare void @BZ2_bz__AssertH__fail()