[CFIFixup] Allow function prologues to span more than one basic block #68984
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@llvm/pr-subscribers-backend-aarch64 Author: Momchil Velikov (momchil-velikov) ChangesThe CFIFixup pass assumes a function prologue is contained in a single basic block. This assumption is broken with upcoming support for stack probing (
Thus, for the prologue CFI instructions, if one is executed then all are executed, there is a total order of executions, and the last instruction in that order can be considered the end of the prologoue for the purpose of inserting the initial That last instruction is found by finding the first block in the post-order traversal which contains prologue CFI instructions. Full diff: https://github.com/llvm/llvm-project/pull/68984.diff 2 Files Affected:
diff --git a/llvm/lib/CodeGen/CFIFixup.cpp b/llvm/lib/CodeGen/CFIFixup.cpp
index 837dbd77d07361a..7269616e3fffab9 100644
--- a/llvm/lib/CodeGen/CFIFixup.cpp
+++ b/llvm/lib/CodeGen/CFIFixup.cpp
@@ -10,20 +10,25 @@
// This pass inserts the necessary instructions to adjust for the inconsistency
// of the call-frame information caused by final machine basic block layout.
// The pass relies in constraints LLVM imposes on the placement of
-// save/restore points (cf. ShrinkWrap):
-// * there is a single basic block, containing the function prologue
+// save/restore points (cf. ShrinkWrap) and has certain preconditions about
+// placement of CFI instructions:
+// * for any two CFI instructions of the function prologue one dominates
+// and is post-dominated by the other
// * possibly multiple epilogue blocks, where each epilogue block is
// complete and self-contained, i.e. CSR restore instructions (and the
// corresponding CFI instructions are not split across two or more blocks.
-// * prologue and epilogue blocks are outside of any loops
-// Thus, during execution, at the beginning and at the end of each basic block
-// the function can be in one of two states:
+// * CFI instructions are not contained in any loops
+// Thus, during execution, at the beginning and at the end of each basic block,
+// following the prologue, the function can be in one of two states:
// - "has a call frame", if the function has executed the prologue, and
// has not executed any epilogue
// - "does not have a call frame", if the function has not executed the
// prologue, or has executed an epilogue
// which can be computed by a single RPO traversal.
+// The location of the prologue is determined by finding the first block in the
+// post-order traversal which contains CFI instructions.
+
// In order to accommodate backends which do not generate unwind info in
// epilogues we compute an additional property "strong no call frame on entry",
// which is set for the entry point of the function and for every block
@@ -85,10 +90,6 @@ static bool isPrologueCFIInstruction(const MachineInstr &MI) {
MI.getFlag(MachineInstr::FrameSetup);
}
-static bool containsPrologue(const MachineBasicBlock &MBB) {
- return llvm::any_of(MBB.instrs(), isPrologueCFIInstruction);
-}
-
static bool containsEpilogue(const MachineBasicBlock &MBB) {
return llvm::any_of(llvm::reverse(MBB), [](const auto &MI) {
return MI.getOpcode() == TargetOpcode::CFI_INSTRUCTION &&
@@ -96,6 +97,24 @@ static bool containsEpilogue(const MachineBasicBlock &MBB) {
});
}
+static MachineBasicBlock *
+findPrologueEnd(MachineFunction &MF, MachineBasicBlock::iterator &PrologueEnd) {
+ MachineBasicBlock *PrologueBlock = nullptr;
+ for (auto It = po_begin(&MF.front()), End = po_end(&MF.front()); It != End; ++It) {
+ MachineBasicBlock *MBB = *It;
+ llvm::for_each(MBB->instrs(), [&](MachineInstr &MI) {
+ if (isPrologueCFIInstruction(MI)) {
+ PrologueBlock = MBB;
+ PrologueEnd = std::next(MI.getIterator());
+ }
+ });
+ if (PrologueBlock)
+ return PrologueBlock;
+ }
+
+ return nullptr;
+}
+
bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
const TargetFrameLowering &TFL = *MF.getSubtarget().getFrameLowering();
if (!TFL.enableCFIFixup(MF))
@@ -105,6 +124,14 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
if (NumBlocks < 2)
return false;
+ // Find the prologue and the point where we can issue the first
+ // `.cfi_remember_state`.
+
+ MachineBasicBlock::iterator PrologueEnd;
+ MachineBasicBlock *PrologueBlock = findPrologueEnd(MF, PrologueEnd);
+ if (PrologueBlock == nullptr)
+ return false;
+
struct BlockFlags {
bool Reachable : 1;
bool StrongNoFrameOnEntry : 1;
@@ -116,21 +143,15 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
BlockInfo[0].StrongNoFrameOnEntry = true;
// Compute the presence/absence of frame at each basic block.
- MachineBasicBlock *PrologueBlock = nullptr;
ReversePostOrderTraversal<MachineBasicBlock *> RPOT(&*MF.begin());
for (MachineBasicBlock *MBB : RPOT) {
BlockFlags &Info = BlockInfo[MBB->getNumber()];
// Set to true if the current block contains the prologue or the epilogue,
// respectively.
- bool HasPrologue = false;
+ bool HasPrologue = MBB == PrologueBlock;
bool HasEpilogue = false;
- if (!PrologueBlock && !Info.HasFrameOnEntry && containsPrologue(*MBB)) {
- PrologueBlock = MBB;
- HasPrologue = true;
- }
-
if (Info.HasFrameOnEntry || HasPrologue)
HasEpilogue = containsEpilogue(*MBB);
@@ -149,9 +170,6 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
}
}
- if (!PrologueBlock)
- return false;
-
// Walk the blocks of the function in "physical" order.
// Every block inherits the frame state (as recorded in the unwind tables)
// of the previous block. If the intended frame state is different, insert
@@ -162,10 +180,7 @@ bool CFIFixup::runOnMachineFunction(MachineFunction &MF) {
// insert a `.cfi_remember_state`, in the case that the current block needs a
// `.cfi_restore_state`.
MachineBasicBlock *InsertMBB = PrologueBlock;
- MachineBasicBlock::iterator InsertPt = PrologueBlock->begin();
- for (MachineInstr &MI : *PrologueBlock)
- if (isPrologueCFIInstruction(MI))
- InsertPt = std::next(MI.getIterator());
+ MachineBasicBlock::iterator InsertPt = PrologueEnd;
assert(InsertPt != PrologueBlock->begin() &&
"Inconsistent notion of \"prologue block\"");
diff --git a/llvm/test/CodeGen/AArch64/cfi-fixup-multi-block-prologue.mir b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-block-prologue.mir
new file mode 100644
index 000000000000000..31fa3832367becc
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/cfi-fixup-multi-block-prologue.mir
@@ -0,0 +1,308 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 3
+# RUN: llc -run-pass=cfi-fixup %s -o - | FileCheck %s
+--- |
+ source_filename = "cfi-fixup.ll"
+ target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+ target triple = "aarch64-linux"
+
+ define i32 @f(i32 %x) #0 {
+ entry:
+ %p = alloca i8, i32 30000, align 1
+ switch i32 %x, label %if.end7 [
+ i32 0, label %return
+ i32 1, label %if.then2
+ i32 2, label %if.then5
+ ]
+
+ if.then2: ; preds = %entry
+ %call = tail call i32 @g1(i32 1)
+ %add = add nsw i32 %call, 1
+ br label %return
+
+ if.then5: ; preds = %entry
+ %call6 = tail call i32 @g0(i32 2)
+ %sub = sub nsw i32 1, %call6
+ br label %return
+
+ if.end7: ; preds = %entry
+ br label %return
+
+ return: ; preds = %if.end7, %if.then5, %if.then2, %entry
+ %retval.0 = phi i32 [ %add, %if.then2 ], [ %sub, %if.then5 ], [ 0, %if.end7 ], [ 1, %entry ]
+ ret i32 %retval.0
+ }
+
+ declare i32 @g1(i32)
+
+ declare i32 @g0(i32)
+
+ attributes #0 = { uwtable "probe-stack"="inline-asm" }
+
+...
+---
+name: f
+alignment: 4
+exposesReturnsTwice: false
+legalized: false
+regBankSelected: false
+selected: false
+failedISel: false
+tracksRegLiveness: true
+hasWinCFI: false
+callsEHReturn: false
+callsUnwindInit: false
+hasEHCatchret: false
+hasEHScopes: false
+hasEHFunclets: false
+isOutlined: false
+debugInstrRef: false
+failsVerification: false
+tracksDebugUserValues: true
+registers: []
+liveins:
+ - { reg: '$w0', virtual-reg: '' }
+frameInfo:
+ isFrameAddressTaken: false
+ isReturnAddressTaken: false
+ hasStackMap: false
+ hasPatchPoint: false
+ stackSize: 30016
+ offsetAdjustment: 0
+ maxAlignment: 8
+ adjustsStack: true
+ hasCalls: true
+ stackProtector: ''
+ functionContext: ''
+ maxCallFrameSize: 0
+ cvBytesOfCalleeSavedRegisters: 0
+ hasOpaqueSPAdjustment: false
+ hasVAStart: false
+ hasMustTailInVarArgFunc: false
+ hasTailCall: false
+ localFrameSize: 30000
+ savePoint: ''
+ restorePoint: ''
+fixedStack: []
+stack:
+ - { id: 0, name: p, type: default, offset: -30016, size: 30000, alignment: 1,
+ stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+ local-offset: -30000, debug-info-variable: '', debug-info-expression: '',
+ debug-info-location: '' }
+ - { id: 1, name: '', type: spill-slot, offset: -8, size: 8, alignment: 8,
+ stack-id: default, callee-saved-register: '$lr', callee-saved-restored: true,
+ debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+ - { id: 2, name: '', type: spill-slot, offset: -16, size: 8, alignment: 8,
+ stack-id: default, callee-saved-register: '$fp', callee-saved-restored: true,
+ debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+entry_values: []
+callSites: []
+debugValueSubstitutions: []
+constants: []
+machineFunctionInfo:
+ hasRedZone: false
+body: |
+ ; CHECK-LABEL: name: f
+ ; CHECK: bb.0.entry:
+ ; CHECK-NEXT: successors: %bb.1(0x80000000)
+ ; CHECK-NEXT: liveins: $w0, $lr, $fp
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: early-clobber $sp = frame-setup STPXpre killed $fp, killed $lr, $sp, -2 :: (store (s64) into %stack.2), (store (s64) into %stack.1)
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa_offset 16
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION offset $w30, -8
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION offset $w29, -16
+ ; CHECK-NEXT: $x9 = frame-setup SUBXri $sp, 7, 12
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa $w9, 28688
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1.entry:
+ ; CHECK-NEXT: successors: %bb.2(0x40000000), %bb.1(0x40000000)
+ ; CHECK-NEXT: liveins: $x9
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: $sp = frame-setup SUBXri $sp, 1, 12
+ ; CHECK-NEXT: $xzr = frame-setup SUBSXrx64 $sp, $x9, 24, implicit-def $nzcv
+ ; CHECK-NEXT: frame-setup STRXui $xzr, $sp, 0
+ ; CHECK-NEXT: frame-setup Bcc 1, %bb.1, implicit killed $nzcv
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2.entry:
+ ; CHECK-NEXT: successors: %bb.6(0x20000000), %bb.3(0x60000000)
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa_register $wsp
+ ; CHECK-NEXT: $sp = frame-setup SUBXri $sp, 1328, 0
+ ; CHECK-NEXT: frame-setup CFI_INSTRUCTION def_cfa_offset 30016
+ ; CHECK-NEXT: CFI_INSTRUCTION remember_state
+ ; CHECK-NEXT: frame-setup STRXui $xzr, $sp, 0
+ ; CHECK-NEXT: CBZW renamable $w0, %bb.6
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.3.entry:
+ ; CHECK-NEXT: successors: %bb.7(0x2aaaaaab), %bb.4(0x55555555)
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: dead $wzr = SUBSWri renamable $w0, 2, 0, implicit-def $nzcv
+ ; CHECK-NEXT: Bcc 0, %bb.7, implicit killed $nzcv
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.4.entry:
+ ; CHECK-NEXT: successors: %bb.5(0x40000000), %bb.8(0x40000000)
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: dead $wzr = SUBSWri renamable $w0, 1, 0, implicit-def $nzcv
+ ; CHECK-NEXT: Bcc 1, %bb.8, implicit killed $nzcv
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.5.if.then2:
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: BL @g1, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
+ ; CHECK-NEXT: renamable $w0 = nsw ADDWri killed renamable $w0, 1, 0
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 7, 12
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 1328, 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ ; CHECK-NEXT: early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w30
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w29
+ ; CHECK-NEXT: RET undef $lr, implicit killed $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.6:
+ ; CHECK-NEXT: CFI_INSTRUCTION restore_state
+ ; CHECK-NEXT: CFI_INSTRUCTION remember_state
+ ; CHECK-NEXT: renamable $w0 = MOVZWi 1, 0
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 7, 12
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 1328, 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ ; CHECK-NEXT: early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w30
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w29
+ ; CHECK-NEXT: RET undef $lr, implicit killed $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.7.if.then5:
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: CFI_INSTRUCTION restore_state
+ ; CHECK-NEXT: CFI_INSTRUCTION remember_state
+ ; CHECK-NEXT: BL @g0, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
+ ; CHECK-NEXT: renamable $w8 = MOVZWi 1, 0
+ ; CHECK-NEXT: $w0 = SUBWrs killed renamable $w8, killed renamable $w0, 0
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 7, 12
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 1328, 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ ; CHECK-NEXT: early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w30
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w29
+ ; CHECK-NEXT: RET undef $lr, implicit killed $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.8.if.end7:
+ ; CHECK-NEXT: CFI_INSTRUCTION restore_state
+ ; CHECK-NEXT: $w0 = ORRWrs $wzr, $wzr, 0
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 7, 12
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 1328, 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ ; CHECK-NEXT: early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w30
+ ; CHECK-NEXT: frame-destroy CFI_INSTRUCTION restore $w29
+ ; CHECK-NEXT: RET undef $lr, implicit killed $w0
+ bb.0.entry:
+ successors: %bb.1(0x80000000)
+ liveins: $w0, $lr, $fp
+
+ early-clobber $sp = frame-setup STPXpre killed $fp, killed $lr, $sp, -2 :: (store (s64) into %stack.2), (store (s64) into %stack.1)
+ frame-setup CFI_INSTRUCTION def_cfa_offset 16
+ frame-setup CFI_INSTRUCTION offset $w30, -8
+ frame-setup CFI_INSTRUCTION offset $w29, -16
+ $x9 = frame-setup SUBXri $sp, 7, 12
+ frame-setup CFI_INSTRUCTION def_cfa $w9, 28688
+
+ bb.1.entry:
+ successors: %bb.2(0x40000000), %bb.1(0x40000000)
+ liveins: $x9
+
+ $sp = frame-setup SUBXri $sp, 1, 12
+ $xzr = frame-setup SUBSXrx64 $sp, $x9, 24, implicit-def $nzcv
+ frame-setup STRXui $xzr, $sp, 0
+ frame-setup Bcc 1, %bb.1, implicit killed $nzcv
+
+ bb.2.entry:
+ successors: %bb.6(0x20000000), %bb.3(0x60000000)
+ liveins: $w0
+
+ frame-setup CFI_INSTRUCTION def_cfa_register $wsp
+ $sp = frame-setup SUBXri $sp, 1328, 0
+ frame-setup CFI_INSTRUCTION def_cfa_offset 30016
+ frame-setup STRXui $xzr, $sp, 0
+ CBZW renamable $w0, %bb.6
+
+ bb.3.entry:
+ successors: %bb.7(0x2aaaaaab), %bb.4(0x55555555)
+ liveins: $w0
+
+ dead $wzr = SUBSWri renamable $w0, 2, 0, implicit-def $nzcv
+ Bcc 0, %bb.7, implicit killed $nzcv
+
+ bb.4.entry:
+ successors: %bb.5(0x40000000), %bb.8(0x40000000)
+ liveins: $w0
+
+ dead $wzr = SUBSWri renamable $w0, 1, 0, implicit-def $nzcv
+ Bcc 1, %bb.8, implicit killed $nzcv
+
+ bb.5.if.then2:
+ liveins: $w0
+
+ BL @g1, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
+ renamable $w0 = nsw ADDWri killed renamable $w0, 1, 0
+ $sp = frame-destroy ADDXri $sp, 7, 12
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ $sp = frame-destroy ADDXri $sp, 1328, 0
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ frame-destroy CFI_INSTRUCTION restore $w30
+ frame-destroy CFI_INSTRUCTION restore $w29
+ RET undef $lr, implicit killed $w0
+
+ bb.6:
+ renamable $w0 = MOVZWi 1, 0
+ $sp = frame-destroy ADDXri $sp, 7, 12
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ $sp = frame-destroy ADDXri $sp, 1328, 0
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ frame-destroy CFI_INSTRUCTION restore $w30
+ frame-destroy CFI_INSTRUCTION restore $w29
+ RET undef $lr, implicit killed $w0
+
+ bb.7.if.then5:
+ liveins: $w0
+
+ BL @g0, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit killed $w0, implicit-def $sp, implicit-def $w0
+ renamable $w8 = MOVZWi 1, 0
+ $w0 = SUBWrs killed renamable $w8, killed renamable $w0, 0
+ $sp = frame-destroy ADDXri $sp, 7, 12
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ $sp = frame-destroy ADDXri $sp, 1328, 0
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ frame-destroy CFI_INSTRUCTION restore $w30
+ frame-destroy CFI_INSTRUCTION restore $w29
+ RET undef $lr, implicit killed $w0
+
+ bb.8.if.end7:
+ $w0 = ORRWrs $wzr, $wzr, 0
+ $sp = frame-destroy ADDXri $sp, 7, 12
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 1344
+ $sp = frame-destroy ADDXri $sp, 1328, 0
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 16
+ early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 0
+ frame-destroy CFI_INSTRUCTION restore $w30
+ frame-destroy CFI_INSTRUCTION restore $w29
+ RET undef $lr, implicit killed $w0
+
+...
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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Sorry for the late reply. I have just cleaned up my exploded inbox after llvm-project's github PR transition and are catching up with the messages. Studying... |
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) Precommit test for #68984
The CFIFixup pass assumes a function prologue is contained in a single basic block. This assumption is broken with upcoming support for stack probing (`-fstack-clash-protection`) in AArch64 - the emitted probing sequence in a prologue may contain loops, i.e. more than one basic block. The generated CFG is not arbitrary though: * CFI instructions are outside of any loops * for any two CFI instructions of the function prologue one dominates and is post-dominated by the other Thus, for the prologue CFI instructions, if one is executed then all are executed, there is a total order of executions, and the last instruction in that order can be considered the end of the prologoue for the purpose of inserting the initial `.cfi_remember_state` directive. That last instruction is found by finding the first block in the post-order traversal which contains prologue CFI instructions.
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…llvm#68984) The CFIFixup pass assumes a function prologue is contained in a single basic block. This assumption is broken with upcoming support for stack probing (`-fstack-clash-protection`) in AArch64 - the emitted probing sequence in a prologue may contain loops, i.e. more than one basic block. The generated CFG is not arbitrary though: * CFI instructions are outside of any loops * for any two CFI instructions of the function prologue one dominates and is post-dominated by the other Thus, for the prologue CFI instructions, if one is executed then all are executed, there is a total order of executions, and the last instruction in that order can be considered the end of the prologoue for the purpose of inserting the initial `.cfi_remember_state` directive. That last instruction is found by finding the first block in the post-order traversal which contains prologue CFI instructions.
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The CFIFixup pass assumes a function prologue is contained in a single basic block. This assumption is broken with upcoming support for stack probing (
-fstack-clash-protection) in AArch64 - the emitted probing sequence in a prologue may contain loops, i.e. more than one basic block. The generated CFG is not arbitrary though:Thus, for the prologue CFI instructions, if one is executed then all are executed, there is a total order of executions, and the last instruction in that order can be considered the end of the prologoue for the purpose of inserting the initial
.cfi_remember_statedirective.That last instruction is found by finding the first block in the post-order traversal which contains prologue CFI instructions.