[llvm] 80fd9f3 - [CSKY] Fix error of underestimated function size by save/restore R15(LR) when we use BSR far jump.
Zi Xuan Wu via llvm-commits
llvm-commits at lists.llvm.org
Tue May 31 20:22:56 PDT 2022
Author: Zi Xuan Wu (Zeson)
Date: 2022-06-01T11:05:19+08:00
New Revision: 80fd9f3e0a185fb285a9b597e020d60bb5dfb9a2
URL: https://github.com/llvm/llvm-project/commit/80fd9f3e0a185fb285a9b597e020d60bb5dfb9a2
DIFF: https://github.com/llvm/llvm-project/commit/80fd9f3e0a185fb285a9b597e020d60bb5dfb9a2.diff
LOG: [CSKY] Fix error of underestimated function size by save/restore R15(LR) when we use BSR far jump.
In CSKYConstantIslands, when fix up an unconditional branch(CSKY::BR32) whose destination is
too far away to fit in its displacement field, and if the R15(LR) register has been
spilled in the prologue, then we can use BSR to implement a far jump. So we need estimate function
size, and spill R15(LR) when the function size >= unconditional branch(CSKY::BR32) can reach.
EstimateFunctionSizeInBytes function adds up all instructions and constant pool entries(each entry is 4 bytes).
Added:
Modified:
llvm/lib/Target/CSKY/CSKYFrameLowering.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Target/CSKY/CSKYFrameLowering.cpp b/llvm/lib/Target/CSKY/CSKYFrameLowering.cpp
index 3bf001c2cee71..9907f39b3f902 100644
--- a/llvm/lib/Target/CSKY/CSKYFrameLowering.cpp
+++ b/llvm/lib/Target/CSKY/CSKYFrameLowering.cpp
@@ -13,6 +13,7 @@
#include "CSKYFrameLowering.h"
#include "CSKYMachineFunctionInfo.h"
#include "CSKYSubtarget.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -270,6 +271,17 @@ void CSKYFrameLowering::emitEpilogue(MachineFunction &MF,
MachineInstr::FrameDestroy);
}
+static unsigned EstimateFunctionSizeInBytes(const MachineFunction &MF,
+ const CSKYInstrInfo &TII) {
+ unsigned FnSize = 0;
+ for (auto &MBB : MF) {
+ for (auto &MI : MBB)
+ FnSize += TII.getInstSizeInBytes(MI);
+ }
+ FnSize += MF.getConstantPool()->getConstants().size() * 4;
+ return FnSize;
+}
+
static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
const CSKYSubtarget &STI) {
unsigned Limit = (1 << 12) - 1;
@@ -349,6 +361,7 @@ void CSKYFrameLowering::determineCalleeSaves(MachineFunction &MF,
CSKYMachineFunctionInfo *CFI = MF.getInfo<CSKYMachineFunctionInfo>();
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
+ const CSKYInstrInfo *TII = STI.getInstrInfo();
const MachineRegisterInfo &MRI = MF.getRegInfo();
MachineFrameInfo &MFI = MF.getFrameInfo();
@@ -411,8 +424,6 @@ void CSKYFrameLowering::determineCalleeSaves(MachineFunction &MF,
}
}
- CFI->setLRIsSpilled(SavedRegs.test(CSKY::R15));
-
unsigned CSStackSize = 0;
for (unsigned Reg : SavedRegs.set_bits()) {
auto RegSize = TRI->getRegSizeInBits(Reg, MRI) / 8;
@@ -432,6 +443,14 @@ void CSKYFrameLowering::determineCalleeSaves(MachineFunction &MF,
RS->addScavengingFrameIndex(MFI.CreateStackObject(size, align, false));
}
+
+ unsigned FnSize = EstimateFunctionSizeInBytes(MF, *TII);
+ // Force R15 to be spilled if the function size is > 65534. This enables
+ // use of BSR to implement far jump.
+ if (FnSize >= ((1 << (16 - 1)) * 2))
+ SavedRegs.set(CSKY::R15);
+
+ CFI->setLRIsSpilled(SavedRegs.test(CSKY::R15));
}
// Not preserve stack space within prologue for outgoing variables when the
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