diff options
| -rw-r--r-- | llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp b/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp index 4630c98b46f..b4a5d2a4876 100644 --- a/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp +++ b/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp @@ -1402,8 +1402,30 @@ bool HexagonPacketizerList::isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) { } } - // Skip over anti-dependences. Two instructions that are anti-dependent - // can share a packet. + // There are certain anti-dependencies that cannot be ignored. + // Specifically: + // J2_call ... %R0<imp-def> ; SUJ + // R0 = ... ; SUI + // Those cannot be packetized together, since the call will observe + // the effect of the assignment to R0. + if (DepType == SDep::Anti && J->isCall()) { + // Check if I defines any volatile register. We should also check + // registers that the call may read, but these happen to be a + // subset of the volatile register set. + for (const MCPhysReg *P = J->getDesc().ImplicitDefs; P && *P; ++P) { + if (!I->modifiesRegister(*P, HRI)) + continue; + FoundSequentialDependence = true; + break; + } + } + + // Skip over remaining anti-dependences. Two instructions that are + // anti-dependent can share a packet, since in most such cases all + // operands are read before any modifications take place. + // The exceptions are branch and call instructions, since they are + // executed after all other instructions have completed (at least + // conceptually). if (DepType != SDep::Anti) { FoundSequentialDependence = true; break; |
