Dynamic stack realignment use of sp register as source/dest register
in "bic sp, sp, #15" leads to unpredicatble behaviour in Thumb2 mode.
Emit the following code instead:
mov r4, sp
bic r4, r4, #15
mov sp, r4
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90724 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index ff11576..9b5f79f 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -578,6 +578,13 @@
MFI->calculateMaxStackAlignment();
}
+ // Spill R4 if Thumb2 function requires stack realignment - it will be used as
+ // scratch register.
+ // FIXME: It will be better just to find spare register here.
+ if (needsStackRealignment(MF) &&
+ AFI->isThumb2Function())
+ MF.getRegInfo().setPhysRegUsed(ARM::R4);
+
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is used.
const unsigned *CSRegs = getCalleeSavedRegs();
@@ -1351,14 +1358,30 @@
// If we need dynamic stack realignment, do it here.
if (needsStackRealignment(MF)) {
- unsigned Opc;
unsigned MaxAlign = MFI->getMaxAlignment();
assert (!AFI->isThumb1OnlyFunction());
- Opc = AFI->isThumbFunction() ? ARM::t2BICri : ARM::BICri;
-
- AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(Opc), ARM::SP)
+ if (!AFI->isThumbFunction()) {
+ // Emit bic sp, sp, MaxAlign
+ AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
+ TII.get(ARM::BICri), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addImm(MaxAlign-1)));
+ } else {
+ // We cannot use sp as source/dest register here, thus we're emitting the
+ // following sequence:
+ // mov r4, sp
+ // bic r4, r4, MaxAlign
+ // mov sp, r4
+ // FIXME: It will be better just to find spare register here.
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::R4)
+ .addReg(ARM::SP, RegState::Kill);
+ AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
+ TII.get(ARM::t2BICri), ARM::R4)
+ .addReg(ARM::R4, RegState::Kill)
+ .addImm(MaxAlign-1)));
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
+ .addReg(ARM::R4, RegState::Kill);
+ }
}
}