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[NFC] [PPCGCodeGeneration] cleanup kills related code. 

We extended kills in Polly to handle both `phi` nodes and scalars that
    are not used within the Scop. Update the comments and choice of
    variable names to reflect this.

llvm-svn: 308279
This commit is contained in:
Siddharth Bhat 2017-07-18 09:15:16 +00:00
parent df4100b3d2
commit edfef5ae8e
1 changed files with 29 additions and 24 deletions
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53
polly/lib/CodeGen/PPCGCodeGeneration.cpp
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@ -129,10 +129,12 @@ struct MustKillsInfo {
/// Map from kill statement instances to scalars that need to be
/// killed.
///
/// We currently only derive kill information for phi nodes, as phi nodes
/// allow us to easily derive kill information. PHI nodes are not alive
/// outside the scop and can consequently all be "killed". [params] -> {
/// [Stmt_phantom[] -> ref_phantom[]] -> phi_ref[] }
/// We currently derive kill information for:
/// 1. phi nodes. PHI nodes are not alive outside the scop and can
/// consequently all be killed.
/// 2. Scalar arrays that are not used outside the Scop. This is
/// checked by `isScalarUsesContainedInScop`.
/// [params] -> { [Stmt_phantom[] -> ref_phantom[]] -> scalar_to_kill[] }
isl::union_map TaggedMustKills;
MustKillsInfo() : KillsSchedule(nullptr), TaggedMustKills(nullptr){};
@ -185,39 +187,42 @@ static MustKillsInfo computeMustKillsInfo(const Scop &S) {
// at the cost of some code complexity.
Info.KillsSchedule = nullptr;
for (isl::id &phiId : KillMemIds) {
for (isl::id &ToKillId : KillMemIds) {
isl::id KillStmtId = isl::id::alloc(
S.getIslCtx(), std::string("SKill_phantom_").append(phiId.get_name()),
nullptr);
S.getIslCtx(),
std::string("SKill_phantom_").append(ToKillId.get_name()), nullptr);
// NOTE: construction of tagged_must_kill:
// 2. We need to construct a map:
// [param] -> { [Stmt_phantom[] -> ref_phantom[]] -> phi_ref }
// [param] -> { [Stmt_phantom[] -> ref_phantom[]] -> scalar_to_kill[] }
// To construct this, we use `isl_map_domain_product` on 2 maps`:
// 2a. StmtToPhi:
// [param] -> { Stmt_phantom[] -> phi_ref[] }
// 2b. PhantomRefToPhi:
// [param] -> { ref_phantom[] -> phi_ref[] }
// 2a. StmtToScalar:
// [param] -> { Stmt_phantom[] -> scalar_to_kill[] }
// 2b. PhantomRefToScalar:
// [param] -> { ref_phantom[] -> scalar_to_kill[] }
//
// Combining these with `isl_map_domain_product` gives us
// TaggedMustKill:
// [param] -> { [Stmt[] -> phantom_ref[]] -> memref[] }
// [param] -> { [Stmt[] -> phantom_ref[]] -> scalar_to_kill[] }
// 2a. [param] -> { S_2[] -> phi_ref[] }
isl::map StmtToPhi = isl::map::universe(isl::space(ParamSpace));
StmtToPhi = StmtToPhi.set_tuple_id(isl::dim::in, isl::id(KillStmtId));
StmtToPhi = StmtToPhi.set_tuple_id(isl::dim::out, isl::id(phiId));
// 2a. [param] -> { Stmt[] -> scalar_to_kill[] }
isl::map StmtToScalar = isl::map::universe(isl::space(ParamSpace));
StmtToScalar = StmtToScalar.set_tuple_id(isl::dim::in, isl::id(KillStmtId));
StmtToScalar = StmtToScalar.set_tuple_id(isl::dim::out, isl::id(ToKillId));
isl::id PhantomRefId = isl::id::alloc(
S.getIslCtx(), std::string("ref_phantom") + phiId.get_name(), nullptr);
S.getIslCtx(), std::string("ref_phantom") + ToKillId.get_name(),
nullptr);
// 2b. [param] -> { phantom_ref[] -> memref[] }
isl::map PhantomRefToPhi = isl::map::universe(isl::space(ParamSpace));
PhantomRefToPhi = PhantomRefToPhi.set_tuple_id(isl::dim::in, PhantomRefId);
PhantomRefToPhi = PhantomRefToPhi.set_tuple_id(isl::dim::out, phiId);
// 2b. [param] -> { phantom_ref[] -> scalar_to_kill[] }
isl::map PhantomRefToScalar = isl::map::universe(isl::space(ParamSpace));
PhantomRefToScalar =
PhantomRefToScalar.set_tuple_id(isl::dim::in, PhantomRefId);
PhantomRefToScalar =
PhantomRefToScalar.set_tuple_id(isl::dim::out, ToKillId);
// 2. [param] -> { [Stmt[] -> phantom_ref[]] -> memref[] }
isl::map TaggedMustKill = StmtToPhi.domain_product(PhantomRefToPhi);
// 2. [param] -> { [Stmt[] -> phantom_ref[]] -> scalar_to_kill[] }
isl::map TaggedMustKill = StmtToScalar.domain_product(PhantomRefToScalar);
Info.TaggedMustKills = Info.TaggedMustKills.unite(TaggedMustKill);
// 3. Create the kill schedule of the form: