Add support for dynamic stack realignment when in thumb1 mode.
rdar://10288916
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142337 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Thumb1FrameLowering.cpp b/lib/Target/ARM/Thumb1FrameLowering.cpp
index d848177..ad1edc8 100644
--- a/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -155,10 +155,32 @@
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
- // Thumb1 does not currently support dynamic stack realignment. Report a
- // fatal error rather then silently generate bad code.
- if (RegInfo->needsStackRealignment(MF))
- report_fatal_error("Dynamic stack realignment not supported for thumb1.");
+ // If we need dynamic stack realignment, do it here. Be paranoid and make
+ // sure if we also have VLAs, we have a base pointer for frame access.
+ if (RegInfo->needsStackRealignment(MF)) {
+ // We cannot use sp as source/dest register here, thus we're emitting the
+ // following sequence:
+ // mov r4, sp
+ // lsrs r4, r4, Log2MaxAlign
+ // lsls r4, r4, Log2MaxAlign
+ // mov sp, r4
+ unsigned MaxAlign = MFI->getMaxAlignment();
+ unsigned Log2MaxAlign = Log2_32(MaxAlign);
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
+ .addReg(ARM::SP, RegState::Kill));
+ AddDefaultPred(AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tLSRri),
+ ARM::R4))
+ .addReg(ARM::R4, RegState::Kill)
+ .addImm(Log2MaxAlign));
+ AddDefaultPred(AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tLSLri),
+ ARM::R4))
+ .addReg(ARM::R4, RegState::Kill)
+ .addImm(Log2MaxAlign));
+ AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
+ .addReg(ARM::R4, RegState::Kill));
+
+ AFI->setShouldRestoreSPFromFP(true);
+ }
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects