[X86] Allow folding of stack reloads when loading a subreg of the spilled reg
We did not support subregs in InlineSpiller:foldMemoryOperand() because targets
may not deal with them correctly.
This adds a target hook to let the spiller know that a target can handle
subregs, and actually enables it for x86 for the case of stack slot reloads.
This fixes PR30832.
Differential Revision: https://reviews.llvm.org/D26521
llvm-svn: 287792
diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 3ccc18d..3e5ae5f 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -739,9 +739,12 @@
bool WasCopy = MI->isCopy();
unsigned ImpReg = 0;
- bool SpillSubRegs = (MI->getOpcode() == TargetOpcode::STATEPOINT ||
- MI->getOpcode() == TargetOpcode::PATCHPOINT ||
- MI->getOpcode() == TargetOpcode::STACKMAP);
+ // Spill subregs if the target allows it.
+ // We always want to spill subregs for stackmap/patchpoint pseudos.
+ bool SpillSubRegs = TII.isSubregFoldable() ||
+ MI->getOpcode() == TargetOpcode::STATEPOINT ||
+ MI->getOpcode() == TargetOpcode::PATCHPOINT ||
+ MI->getOpcode() == TargetOpcode::STACKMAP;
// TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
// operands.
@@ -754,7 +757,7 @@
ImpReg = MO.getReg();
continue;
}
- // FIXME: Teach targets to deal with subregs.
+
if (!SpillSubRegs && MO.getSubReg())
return false;
// We cannot fold a load instruction into a def.