Be less aggressive about hinting in RAFast.
In particular, don't spill dirty registers only to satisfy a hint. It is
not worth it.
The attached test case provides an example where the fast allocator
would spill a register when other registers are available.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132900 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 9765203..65ebdf8 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -487,14 +487,12 @@
// Take hint when possible.
if (Hint) {
- switch(calcSpillCost(Hint)) {
- default:
- definePhysReg(MI, Hint, regFree);
- // Fall through.
- case 0:
+ // Ignore the hint if we would have to spill a dirty register.
+ unsigned Cost = calcSpillCost(Hint);
+ if (Cost < spillDirty) {
+ if (Cost)
+ definePhysReg(MI, Hint, regFree);
return assignVirtToPhysReg(LRE, Hint);
- case spillImpossible:
- break;
}
}