AMDGPU: Figure out private memory regs after lowering

Introduce pseudo-registers for registers needed for stack
access, which are replaced during finalizeLowering.
Note these pseudo-registers are currently only used for the
used register location, and not for determining their
input argument register.

This is better because it avoids the need to try to predict
whether a call will be emitted from the IR, and also
detects stack objects introduced by legalization.

Test changes are from the HasStackObjects check being more
accurate since stack objects introduced during legalization
are now known.

llvm-svn: 308325

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
index ef6ad4ad0c8..4a3fbb4593b 100644
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -207,7 +207,11 @@ BitVector SIRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
     assert(!isSubRegister(ScratchRSrcReg, ScratchWaveOffsetReg));
   }
 
+  // We have to assume the SP is needed in case there are calls in the function,
+  // which is detected after the function is lowered. If we aren't really going
+  // to need SP, don't bother reserving it.
   unsigned StackPtrReg = MFI->getStackPtrOffsetReg();
+
   if (StackPtrReg != AMDGPU::NoRegister) {
     reserveRegisterTuples(Reserved, StackPtrReg);
     assert(!isSubRegister(ScratchRSrcReg, StackPtrReg));