intel/llvm
1
0
Fork 0
mirror of https://github.com/intel/llvm.git synced 2026-01-18 16:50:51 +08:00
Code Issues Packages Projects Releases Wiki Activity

ARM: don't return by popping PC if we have to adjust the stack afterwards.

Browse Source 
In mandatory tail calling conventions we might have to deallocate stack
space used by our arguments before return. This happens after popping
CSRs, so the pop cannot be turned into the return itself in this case.

The else branch here was already a nop, so removing it as a tidy-up.
This commit is contained in:
Tim Northover
2021-07-21 09:06:51 +01:00
parent 291e0daa6e
commit 19d2e42be2
2 changed files with 21 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
llvm/lib/Target/ARM/ARMFrameLowering.cpp
View File

@@ -1229,19 +1229,16 @@ void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
// The aligned reloads from area DPRCS2 are not inserted here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt &&
!isCmseEntry && !isTrap && STI.hasV5TOps()) {
if (MBB.succ_empty()) {
Reg = ARM::PC;
// Fold the return instruction into the LDM.
DeleteRet = true;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
// We 'restore' LR into PC so it is not live out of the return block:
// Clear Restored bit.
Info.setRestored(false);
} else
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
!isCmseEntry && !isTrap && AFI->getArgumentStackToRestore() == 0 &&
STI.hasV5TOps() && MBB.succ_empty()) {
Reg = ARM::PC;
// Fold the return instruction into the LDM.
DeleteRet = true;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
// We 'restore' LR into PC so it is not live out of the return block:
// Clear Restored bit.
Info.setRestored(false);
}
// If NoGap is true, pop consecutive registers and then leave the rest

12
llvm/test/CodeGen/ARM/tailcc-call.ll
View File

@@ -191,3 +191,15 @@ define tailcc void @fromtail_toC() {
call void @Ccallee_stack4([4 x i32] undef, i32 42)
ret void
}
; Don't try to return by popping pc if there's stack to reclaim.
define tailcc void @notail_stackclean([4 x i32], i32) {
; COMMON-LABEL: notail_stackclean:
; COMMON: pop {r7, lr}
; COMMON: add sp, #8
; COMMON: bx lr
call void @callee_stack0()
ret void
}