[PATCH] D70379: [AMDGPU] Reserving VGPR for future SGPR Spill

[Saiyedul Islam via Phabricator via llvm-commits]

saiislam created this revision.
saiislam added reviewers: arsenm, rampitec, msearles.
saiislam added a project: AMDGPU.
Herald added subscribers: llvm-commits, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.

VGPR register is allocated to handle a future spill of SGPR.


https://reviews.llvm.org/D70379

Files:
  llvm/lib/Target/AMDGPU/SIISelLowering.cpp


Index: llvm/lib/Target/AMDGPU/SIISelLowering.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -100,6 +100,11 @@
   cl::desc("Do not align and prefetch loops"),
   cl::init(false));
 
+static cl::opt<bool> VGPRReserveforSGPRSpill(
+  "amdgpu-reserve-vgpr-for-sgpr-spill",
+  cl::desc("Allocates one VGPR for future SGPR Spill"),
+  cl::init(false));
+
 static unsigned findFirstFreeSGPR(CCState &CCInfo) {
   unsigned NumSGPRs = AMDGPU::SGPR_32RegClass.getNumRegs();
   for (unsigned Reg = 0; Reg < NumSGPRs; ++Reg) {
@@ -10745,6 +10750,7 @@
   const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
   const SIRegisterInfo *TRI = Subtarget->getRegisterInfo();
 
+
   if (Info->isEntryFunction()) {
     // Callable functions have fixed registers used for stack access.
     reservePrivateMemoryRegs(getTargetMachine(), MF, *TRI, *Info);
@@ -10790,6 +10796,15 @@
   }
 
   TargetLoweringBase::finalizeLowering(MF);
+
+  // Allocate a VGPR for future SGPR Spill if
+  // "amdgpu-reserve-vgpr-for-sgpr-spill" option is used
+  if (VGPRReserveforSGPRSpill) {
+    int fi = MF.getFrameInfo().CreateStackObject(4,4,false, nullptr, TargetStackID::SGPRSpill);
+    Info->allocateSGPRSpillToVGPR(MF, fi);
+    MF.getFrameInfo().RemoveStackObject(fi);
+  }
+
 }
 
 void SITargetLowering::computeKnownBitsForFrameIndex(const SDValue Op,


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D70379.229763.patch
Type: text/x-patch
Size: 1447 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20191118/8b0a43c2/attachment.bin>