[llvm] [SystemZ] Eliminate call sequence instructions early. (PR #77812)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 27 06:30:57 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-systemz
Author: Jonas Paulsson (JonPsson1)
<details>
<summary>Changes</summary>
On SystemZ, the outgoing argument area which is big enough for all calls in the function is created once during the prolog, as opposed to adjusting the stack around each call. The call-sequence instructions are therefore not really useful any more than to compute the maximum call frame size, which has so far been done by PEI, but can just as well be done at an earlier point.
This patch removes the mapping of the CallFrameSetupOpcode and CallFrameDestroyOpcode and instead computes the MaxCallFrameSize directly after instruction selection and then removes the ADJCALLSTACK pseudos. This removes the confusing pseudos and also avoids the problem of having to keep the call frame size accurate when creating new MBBs.
This fixes #<!-- -->76618 which exposed the need to maintain the call frame size when splitting blocks (which was not done).
---
Full diff: https://github.com/llvm/llvm-project/pull/77812.diff
6 Files Affected:
- (modified) llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp (+14-16)
- (modified) llvm/lib/Target/SystemZ/SystemZFrameLowering.h (-3)
- (modified) llvm/lib/Target/SystemZ/SystemZISelLowering.cpp (+28)
- (modified) llvm/lib/Target/SystemZ/SystemZISelLowering.h (+2)
- (modified) llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp (+1-1)
- (modified) llvm/lib/Target/SystemZ/SystemZInstrInfo.td (+3-3)
``````````diff
diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 80c994a32ea96a..dc7e6589b48af2 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -66,22 +66,6 @@ SystemZFrameLowering::create(const SystemZSubtarget &STI) {
return std::make_unique<SystemZELFFrameLowering>();
}
-MachineBasicBlock::iterator SystemZFrameLowering::eliminateCallFramePseudoInstr(
- MachineFunction &MF, MachineBasicBlock &MBB,
- MachineBasicBlock::iterator MI) const {
- switch (MI->getOpcode()) {
- case SystemZ::ADJCALLSTACKDOWN:
- case SystemZ::ADJCALLSTACKUP:
- assert(hasReservedCallFrame(MF) &&
- "ADJSTACKDOWN and ADJSTACKUP should be no-ops");
- return MBB.erase(MI);
- break;
-
- default:
- llvm_unreachable("Unexpected call frame instruction");
- }
-}
-
namespace {
struct SZFrameSortingObj {
bool IsValid = false; // True if we care about this Object.
@@ -439,6 +423,16 @@ bool SystemZELFFrameLowering::restoreCalleeSavedRegisters(
return true;
}
+static void removeCallSeqPseudos(MachineFunction &MF) {
+ // TODO: These could have been removed in finalize isel already as they are
+ // not mapped as frame instructions. See comment in emitAdjCallStack().
+ for (auto &MBB : MF)
+ for (MachineInstr &MI : llvm::make_early_inc_range(MBB))
+ if (MI.getOpcode() == SystemZ::ADJCALLSTACKDOWN ||
+ MI.getOpcode() == SystemZ::ADJCALLSTACKUP)
+ MI.eraseFromParent();
+}
+
void SystemZELFFrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF, RegScavenger *RS) const {
MachineFrameInfo &MFFrame = MF.getFrameInfo();
@@ -480,6 +474,8 @@ void SystemZELFFrameLowering::processFunctionBeforeFrameFinalized(
ZFI->getRestoreGPRRegs().LowGPR != SystemZ::R6D)
for (auto &MO : MRI->use_nodbg_operands(SystemZ::R6D))
MO.setIsKill(false);
+
+ removeCallSeqPseudos(MF);
}
// Emit instructions before MBBI (in MBB) to add NumBytes to Reg.
@@ -1471,6 +1467,8 @@ void SystemZXPLINKFrameLowering::processFunctionBeforeFrameFinalized(
// with existing compilers.
MFFrame.setMaxCallFrameSize(
std::max(64U, (unsigned)alignTo(MFFrame.getMaxCallFrameSize(), 64)));
+
+ removeCallSeqPseudos(MF);
}
// Determines the size of the frame, and creates the deferred spill objects.
diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.h b/llvm/lib/Target/SystemZ/SystemZFrameLowering.h
index 95f30e3c0d99c8..03ce8882c4de5d 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.h
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.h
@@ -41,9 +41,6 @@ class SystemZFrameLowering : public TargetFrameLowering {
}
bool hasReservedCallFrame(const MachineFunction &MF) const override;
- MachineBasicBlock::iterator
- eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
- MachineBasicBlock::iterator MI) const override;
};
class SystemZELFFrameLowering : public SystemZFrameLowering {
diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index da4bcd7f0c66ed..196903fa4d3202 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -8197,6 +8197,30 @@ static void createPHIsForSelects(SmallVector<MachineInstr*, 8> &Selects,
MF->getProperties().reset(MachineFunctionProperties::Property::NoPHIs);
}
+MachineBasicBlock *
+SystemZTargetLowering::emitAdjCallStack(MachineInstr &MI,
+ MachineBasicBlock *BB) const {
+ MachineFunction &MF = *BB->getParent();
+ MachineFrameInfo &MFI = MF.getFrameInfo();
+ auto *TFL = Subtarget.getFrameLowering<SystemZFrameLowering>();
+ assert(TFL->hasReservedCallFrame(MF) &&
+ "ADJSTACKDOWN and ADJSTACKUP should be no-ops");
+ // Get the MaxCallFrameSize value and clear the NumBytes value to not
+ // confuse the verifier. Keep them around as scheduling barriers around
+ // call arguments even though they serve no further purpose as the call
+ // frame is statically reserved in the prolog.
+ uint32_t NumBytes = MI.getOperand(0).getImm();
+ if (NumBytes > MFI.getMaxCallFrameSize())
+ MFI.setMaxCallFrameSize(NumBytes);
+ // Set AdjustsStack as this is *not* mapped as a frame instruction.
+ MFI.setAdjustsStack(true);
+
+ // TODO: Fix machine scheduler and erase MI instead?
+ MI.getOperand(0).setImm(0);
+
+ return BB;
+}
+
// Implement EmitInstrWithCustomInserter for pseudo Select* instruction MI.
MachineBasicBlock *
SystemZTargetLowering::emitSelect(MachineInstr &MI,
@@ -9400,6 +9424,10 @@ getBackchainAddress(SDValue SP, SelectionDAG &DAG) const {
MachineBasicBlock *SystemZTargetLowering::EmitInstrWithCustomInserter(
MachineInstr &MI, MachineBasicBlock *MBB) const {
switch (MI.getOpcode()) {
+ case SystemZ::ADJCALLSTACKDOWN:
+ case SystemZ::ADJCALLSTACKUP:
+ return emitAdjCallStack(MI, MBB);
+
case SystemZ::Select32:
case SystemZ::Select64:
case SystemZ::Select128:
diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.h b/llvm/lib/Target/SystemZ/SystemZISelLowering.h
index 4943c5cb703c33..7140287a886ccf 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.h
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.h
@@ -760,6 +760,8 @@ class SystemZTargetLowering : public TargetLowering {
MachineBasicBlock *Target) const;
// Implement EmitInstrWithCustomInserter for individual operation types.
+ MachineBasicBlock *emitAdjCallStack(MachineInstr &MI,
+ MachineBasicBlock *BB) const;
MachineBasicBlock *emitSelect(MachineInstr &MI, MachineBasicBlock *BB) const;
MachineBasicBlock *emitCondStore(MachineInstr &MI, MachineBasicBlock *BB,
unsigned StoreOpcode, unsigned STOCOpcode,
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index 2a6dce863c28f1..950548abcfa92c 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -59,7 +59,7 @@ static uint64_t allOnes(unsigned int Count) {
void SystemZInstrInfo::anchor() {}
SystemZInstrInfo::SystemZInstrInfo(SystemZSubtarget &sti)
- : SystemZGenInstrInfo(SystemZ::ADJCALLSTACKDOWN, SystemZ::ADJCALLSTACKUP),
+ : SystemZGenInstrInfo(-1, -1),
RI(sti.getSpecialRegisters()->getReturnFunctionAddressRegister()),
STI(sti) {}
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.td b/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
index 96ea65b6c3d881..7f3a143aad9709 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.td
@@ -13,9 +13,9 @@ def IsTargetELF : Predicate<"Subtarget->isTargetELF()">;
// Stack allocation
//===----------------------------------------------------------------------===//
-// The callseq_start node requires the hasSideEffects flag, even though these
-// instructions are noops on SystemZ.
-let hasNoSchedulingInfo = 1, hasSideEffects = 1 in {
+// These pseudos carry values needed to compute the MaxcallFrameSize of the
+// function. The callseq_start node requires the hasSideEffects flag.
+let usesCustomInserter = 1, hasNoSchedulingInfo = 1, hasSideEffects = 1 in {
def ADJCALLSTACKDOWN : Pseudo<(outs), (ins i64imm:$amt1, i64imm:$amt2),
[(callseq_start timm:$amt1, timm:$amt2)]>;
def ADJCALLSTACKUP : Pseudo<(outs), (ins i64imm:$amt1, i64imm:$amt2),
``````````
</details>
https://github.com/llvm/llvm-project/pull/77812
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