[X86][SSE] Improve cost model for i64 vector comparisons on pre-SSE42 targets
As discussed on PR24888, until SSE42 we don't have access to PCMPGTQ for v2i64 comparisons, but the cost models don't reflect this, resulting in over-optimistic vectorizaton.
This patch adds SSE2 'base level' costs that match what a typical target is capable of and only reduces the v2i64 costs at SSE42.
Technically SSE41 provides a PCMPEQQ v2i64 equality test, but as getCmpSelInstrCost doesn't give us a way to discriminate between comparison test types we can't easily make use of this, otherwise we could split the cost of integer equality and greater-than tests to give better costings of each.
Differential Revision: http://reviews.llvm.org/D20057
llvm-svn: 268972
diff --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index 6ffef16..28ae96d 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -857,13 +857,17 @@
int ISD = TLI->InstructionOpcodeToISD(Opcode);
assert(ISD && "Invalid opcode");
+ static const CostTblEntry SSE2CostTbl[] = {
+ { ISD::SETCC, MVT::v2i64, 8 },
+ { ISD::SETCC, MVT::v4i32, 1 },
+ { ISD::SETCC, MVT::v8i16, 1 },
+ { ISD::SETCC, MVT::v16i8, 1 },
+ };
+
static const CostTblEntry SSE42CostTbl[] = {
{ ISD::SETCC, MVT::v2f64, 1 },
{ ISD::SETCC, MVT::v4f32, 1 },
{ ISD::SETCC, MVT::v2i64, 1 },
- { ISD::SETCC, MVT::v4i32, 1 },
- { ISD::SETCC, MVT::v8i16, 1 },
- { ISD::SETCC, MVT::v16i8, 1 },
};
static const CostTblEntry AVX1CostTbl[] = {
@@ -906,6 +910,10 @@
if (const auto *Entry = CostTableLookup(SSE42CostTbl, ISD, MTy))
return LT.first * Entry->Cost;
+ if (ST->hasSSE2())
+ if (const auto *Entry = CostTableLookup(SSE2CostTbl, ISD, MTy))
+ return LT.first * Entry->Cost;
+
return BaseT::getCmpSelInstrCost(Opcode, ValTy, CondTy);
}