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X86 machine model: reduce SandyBridge and Haswell ILPWindow.

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The initial values were arbitrary. I want them to be more
conservative. This represents the number of latency cycles hidden by
OOO execution. In practice, I think it should be within a small factor
of the complex floating point operation latency so the scheduler can
make some attempt to hide latency even for smallish blocks.

These are by no means the best values, just a starting point for
tuning heuristics. Some benchmarks such as TSVC run faster with this
lower value for SandyBridge. I haven't run anything on Haswell, but
it's shouldn't be 2x SB.

llvm-svn: 179450
This commit is contained in:
Andrew Trick 2013-04-13 06:07:43 +00:00
parent 861493bc4f
commit 835ac00f78
2 changed files with 2 additions and 2 deletions
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2
lib/Target/X86/X86SchedHaswell.td
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@ -18,7 +18,7 @@ def HaswellModel : SchedMachineModel {
let IssueWidth = 4;
let MinLatency = 0; // 0 = Out-of-order execution.
let LoadLatency = 4;
let ILPWindow = 40;
let ILPWindow = 30;
let MispredictPenalty = 16;
}

2
lib/Target/X86/X86SchedSandyBridge.td
View File

@ -19,7 +19,7 @@ def SandyBridgeModel : SchedMachineModel {
let IssueWidth = 4;
let MinLatency = 0; // 0 = Out-of-order execution.
let LoadLatency = 4;
let ILPWindow = 30;
let ILPWindow = 20;
let MispredictPenalty = 16;
}