TargetLowering interface to set/get minimum block entries for jump tables.
Provide interface in TargetLowering to set or get the minimum number of basic
blocks whereby jump tables are generated for switch statements rather than an
if sequence.
getMinimumJumpTableEntries() defaults to 4.
setMinimumJumpTableEntries() allows target configuration.
This patch changes the default for the Hexagon architecture to 5
as it improves performance on some benchmarks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164628 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 483b051..f71c8b8 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2093,7 +2093,7 @@
for (CaseItr I = CR.Range.first, E = CR.Range.second; I != E; ++I)
TSize += I->size();
- if (!areJTsAllowed(TLI) || TSize.ult(4))
+ if (!areJTsAllowed(TLI) || TSize.ult(TLI.getMinimumJumpTableEntries()))
return false;
APInt Range = ComputeRange(First, Last);
@@ -2565,9 +2565,10 @@
if (handleSmallSwitchRange(CR, WorkList, SV, Default, SwitchMBB))
continue;
- // If the switch has more than 5 blocks, and at least 40% dense, and the
+ // If the switch has more than N blocks, and is at least 40% dense, and the
// target supports indirect branches, then emit a jump table rather than
// lowering the switch to a binary tree of conditional branches.
+ // N defaults to 4 and is controlled via TLS.getMinimumJumpTableEntries().
if (handleJTSwitchCase(CR, WorkList, SV, Default, SwitchMBB))
continue;