AMDGPU/SI: Make sure MIMG descriptors and samplers stay in SGPRs

Summary:
It's possible to have resource descriptors and samplers stored in
VGPRs, either by a VMEM instruction or in the case of samplers,
floating-point calculations.  When this happens, we need to use
v_readfirstlane to copy these values back to sgprs.

Reviewers: mareko, arsenm

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D17102

llvm-svn: 260599

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
index 025ed2b5b76..ef1c25b4304 100644
--- a/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -479,6 +479,24 @@ const TargetRegisterClass *SIRegisterInfo::getEquivalentVGPRClass(
   }
 }
 
+const TargetRegisterClass *SIRegisterInfo::getEquivalentSGPRClass(
+                                         const TargetRegisterClass *VRC) const {
+  switch (VRC->getSize()) {
+  case 4:
+    return &AMDGPU::SGPR_32RegClass;
+  case 8:
+    return &AMDGPU::SReg_64RegClass;
+  case 16:
+    return &AMDGPU::SReg_128RegClass;
+  case 32:
+    return &AMDGPU::SReg_256RegClass;
+  case 64:
+    return &AMDGPU::SReg_512RegClass;
+  default:
+    llvm_unreachable("Invalid register class size");
+  }
+}
+
 const TargetRegisterClass *SIRegisterInfo::getSubRegClass(
                          const TargetRegisterClass *RC, unsigned SubIdx) const {
   if (SubIdx == AMDGPU::NoSubRegister)