X86 machine model: reduce SandyBridge and Haswell ILPWindow.

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179450 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86SchedHaswell.td b/lib/Target/X86/X86SchedHaswell.td
index 7de6791f2e48f44177875b38439fa0071ef5c6b9..84c9203c3787b2aa518bd1ab725a409ea6edea8c 100644 (file)
--- a/lib/Target/X86/X86SchedHaswell.td
+++ b/lib/Target/X86/X86SchedHaswell.td
@@ -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;
 }
 

diff --git a/lib/Target/X86/X86SchedSandyBridge.td b/lib/Target/X86/X86SchedSandyBridge.td
index 74d5f1b6eba8bd209d29c04bb960ce701c8480d1..b36b3ad947e060e197f808884e3452e3ded86a1a 100644 (file)
--- a/lib/Target/X86/X86SchedSandyBridge.td
+++ b/lib/Target/X86/X86SchedSandyBridge.td
@@ -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;
 }