[llvm] d867634 - [CostModel][X86] Update comment describing source of costs - we now use llvm-mca more than IACA

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2021-07-02T14:29:32+01:00
New Revision: d867634fbdb1f1f521981c244c410a9b839c8325

URL: https://github.com/llvm/llvm-project/commit/d867634fbdb1f1f521981c244c410a9b839c8325
DIFF: https://github.com/llvm/llvm-project/commit/d867634fbdb1f1f521981c244c410a9b839c8325.diff

LOG: [CostModel][X86] Update comment describing source of costs - we now use llvm-mca more than IACA

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86TargetTransformInfo.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index 9eb5abe4dd9b..9064cca9da52 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -2074,9 +2074,9 @@ InstructionCost X86TTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
   };
 
   static const TypeConversionCostTblEntry SSE2ConversionTbl[] = {
-    // These are somewhat magic numbers justified by looking at the output of
-    // Intel's IACA, running some kernels and making sure when we take
-    // legalization into account the throughput will be overestimated.
+    // These are somewhat magic numbers justified by comparing the
+    // output of llvm-mca for our various supported scheduler models
+    // and basing it off the worst case scenario.
     { ISD::SINT_TO_FP,  MVT::v4f32,  MVT::v16i8,  3 },
     { ISD::SINT_TO_FP,  MVT::v2f64,  MVT::v16i8,  4 },
     { ISD::SINT_TO_FP,  MVT::v4f32,  MVT::v8i16,  3 },