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When pruning candidate formulae out of an LSRUse, update the

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LSRUse's Regs set after all pruning is done, rather than trying
to do it on the fly, which can produce an incomplete result.

This fixes a case where heuristic pruning was stripping all
formulae from a use, which led the solver to enter an infinite
loop.

Also, add a few asserts to diagnose this kind of situation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103328 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-05-07 23:36:59 +00:00
parent c665a5146d
commit 59dc60337f
2 changed files with 94 additions and 3 deletions
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14
lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -2592,9 +2592,6 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
LSRUse &LU = Uses[LUIdx];
FormulaSorter Sorter(L, LU, SE, DT);
// Clear out the set of used regs; it will be recomputed.
LU.Regs.clear();
for (size_t FIdx = 0, NumForms = LU.Formulae.size();
FIdx != NumForms; ++FIdx) {
Formula &F = LU.Formulae[FIdx];
@ -2632,9 +2629,18 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
--NumForms;
continue;
}
}
// Now that we've filtered out some formulae, recompute the Regs set.
LU.Regs.clear();
for (size_t FIdx = 0, NumForms = LU.Formulae.size();
FIdx != NumForms; ++FIdx) {
Formula &F = LU.Formulae[FIdx];
if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
}
// Reset this to prepare for the next use.
BestFormulae.clear();
}
@ -2718,6 +2724,7 @@ void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
LU.Formulae.pop_back();
--e;
--i;
assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
continue;
}
@ -2810,6 +2817,7 @@ retry:
// If none of the formulae had all of the required registers, relax the
// constraint so that we don't exclude all formulae.
if (!AnySatisfiedReqRegs) {
assert(!ReqRegs.empty() && "Solver failed even without required registers");
ReqRegs.clear();
goto retry;
}

83
test/CodeGen/X86/lsr-delayed-fold.ll
View File

@ -49,3 +49,86 @@ lbl_264: ; preds = %if.end, %lbl_264.pr
%tobool12 = icmp eq i8 %mul.i18, 0 ; <i1> [#uses=1]
unreachable
}
; LSR ends up going into conservative pruning mode; don't prune the solution
; so far that it becomes unsolvable though.
; PR7077
%struct.Bu = type { i32, i32, i32 }
define void @_Z3fooP2Bui(%struct.Bu* nocapture %bu) {
entry:
br label %for.body
for.body: ; preds = %for.inc131, %entry
%indvar = phi i64 [ %indvar.next, %for.inc131 ], [ 0, %entry ] ; <i64> [#uses=3]
br i1 undef, label %for.inc131, label %lor.lhs.false
lor.lhs.false: ; preds = %for.body
%tmp15 = add i64 %indvar, 1 ; <i64> [#uses=1]
%tmp17 = add i64 %indvar, 2 ; <i64> [#uses=1]
%tmp19 = add i64 %indvar, 3 ; <i64> [#uses=1]
%tmp21 = add i64 %indvar, 4 ; <i64> [#uses=1]
%tmp23 = add i64 %indvar, 5 ; <i64> [#uses=1]
%tmp25 = add i64 %indvar, 6 ; <i64> [#uses=1]
%tmp27 = add i64 %indvar, 7 ; <i64> [#uses=1]
%tmp29 = add i64 %indvar, 8 ; <i64> [#uses=1]
%tmp31 = add i64 %indvar, 9 ; <i64> [#uses=1]
%tmp35 = add i64 %indvar, 11 ; <i64> [#uses=1]
%tmp37 = add i64 %indvar, 12 ; <i64> [#uses=1]
%tmp39 = add i64 %indvar, 13 ; <i64> [#uses=1]
%tmp41 = add i64 %indvar, 14 ; <i64> [#uses=1]
%tmp43 = add i64 %indvar, 15 ; <i64> [#uses=1]
%tmp45 = add i64 %indvar, 16 ; <i64> [#uses=1]
%tmp47 = add i64 %indvar, 17 ; <i64> [#uses=1]
%mul = trunc i64 %indvar to i32 ; <i32> [#uses=1]
%add22 = trunc i64 %tmp15 to i32 ; <i32> [#uses=1]
%add28 = trunc i64 %tmp17 to i32 ; <i32> [#uses=1]
%add34 = trunc i64 %tmp19 to i32 ; <i32> [#uses=1]
%add40 = trunc i64 %tmp21 to i32 ; <i32> [#uses=1]
%add46 = trunc i64 %tmp23 to i32 ; <i32> [#uses=1]
%add52 = trunc i64 %tmp25 to i32 ; <i32> [#uses=1]
%add58 = trunc i64 %tmp27 to i32 ; <i32> [#uses=1]
%add64 = trunc i64 %tmp29 to i32 ; <i32> [#uses=1]
%add70 = trunc i64 %tmp31 to i32 ; <i32> [#uses=1]
%add82 = trunc i64 %tmp35 to i32 ; <i32> [#uses=1]
%add88 = trunc i64 %tmp37 to i32 ; <i32> [#uses=1]
%add94 = trunc i64 %tmp39 to i32 ; <i32> [#uses=1]
%add100 = trunc i64 %tmp41 to i32 ; <i32> [#uses=1]
%add106 = trunc i64 %tmp43 to i32 ; <i32> [#uses=1]
%add112 = trunc i64 %tmp45 to i32 ; <i32> [#uses=1]
%add118 = trunc i64 %tmp47 to i32 ; <i32> [#uses=1]
%tmp10 = getelementptr %struct.Bu* %bu, i64 %indvar, i32 2 ; <i32*> [#uses=1]
%tmp11 = load i32* %tmp10 ; <i32> [#uses=0]
tail call void undef(i32 %add22)
tail call void undef(i32 %add28)
tail call void undef(i32 %add34)
tail call void undef(i32 %add40)
tail call void undef(i32 %add46)
tail call void undef(i32 %add52)
tail call void undef(i32 %add58)
tail call void undef(i32 %add64)
tail call void undef(i32 %add70)
tail call void undef(i32 %add82)
tail call void undef(i32 %add88)
tail call void undef(i32 %add94)
tail call void undef(i32 %add100)
tail call void undef(i32 %add106)
tail call void undef(i32 %add112)
tail call void undef(i32 %add118)
br label %for.body123
for.body123: ; preds = %for.body123, %lor.lhs.false
%j.03 = phi i32 [ 0, %lor.lhs.false ], [ %inc, %for.body123 ] ; <i32> [#uses=2]
%add129 = add i32 %mul, %j.03 ; <i32> [#uses=1]
tail call void undef(i32 %add129)
%inc = add nsw i32 %j.03, 1 ; <i32> [#uses=1]
br i1 undef, label %for.inc131, label %for.body123
for.inc131: ; preds = %for.body123, %for.body
%indvar.next = add i64 %indvar, 1 ; <i64> [#uses=1]
br i1 undef, label %for.end134, label %for.body
for.end134: ; preds = %for.inc131
ret void
}