AMDGPU: Avoid assertions after SGPR spilling failed

Summary:
The comment explains it: emitError does not necessarily exit the compilation
process, and then using NoRegister leads to assertions later on.
This generates incorrect code, of course, but the user should know to not use
the result when an error has been emitted.

It would be nice to have a test-case for this inside the LLVM repository,
but llc exits on error. shader-db tests trigger the underlying issue at least
on Tonga.

Reviewers: arsenm, tstellarAMD, mareko

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D15826

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256757 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp b/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
index 935aad427198f23b527e424a105536fdea0a0857..bf15516bea7b6f33ceeb48ae915316554690b3b7 100644 (file)
--- a/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
+++ b/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
@@ -156,6 +156,17 @@ SIMachineFunctionInfo::SpilledReg SIMachineFunctionInfo::getSpilledReg(
 
   if (!LaneVGPRs.count(LaneVGPRIdx)) {
     unsigned LaneVGPR = TRI->findUnusedRegister(MRI, &AMDGPU::VGPR_32RegClass);
+
+    if (LaneVGPR == AMDGPU::NoRegister) {
+      LLVMContext &Ctx = MF->getFunction()->getContext();
+      Ctx.emitError("Ran out of VGPRs for spilling SGPR");
+
+      // When compiling from inside Mesa, the compilation continues.
+      // Select an arbitrary register to avoid triggering assertions
+      // during subsequent passes.
+      LaneVGPR = AMDGPU::VGPR0;
+    }
+
     LaneVGPRs[LaneVGPRIdx] = LaneVGPR;
 
     // Add this register as live-in to all blocks to avoid machine verifer

diff --git a/lib/Target/AMDGPU/SIRegisterInfo.cpp b/lib/Target/AMDGPU/SIRegisterInfo.cpp
index 3cdffef0558310bcc56f911e2621b8e08159bc86..353c2b930637645f9dce0aaf04435913258d1453 100644 (file)
--- a/lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ b/lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -282,11 +282,6 @@ void SIRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator MI,
         struct SIMachineFunctionInfo::SpilledReg Spill =
             MFI->getSpilledReg(MF, Index, i);
 
-        if (Spill.VGPR == AMDGPU::NoRegister) {
-           LLVMContext &Ctx = MF->getFunction()->getContext();
-           Ctx.emitError("Ran out of VGPRs for spilling SGPR");
-        }
-
         BuildMI(*MBB, MI, DL,
                 TII->getMCOpcodeFromPseudo(AMDGPU::V_WRITELANE_B32),
                 Spill.VGPR)
@@ -315,11 +310,6 @@ void SIRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator MI,
         struct SIMachineFunctionInfo::SpilledReg Spill =
             MFI->getSpilledReg(MF, Index, i);
 
-        if (Spill.VGPR == AMDGPU::NoRegister) {
-           LLVMContext &Ctx = MF->getFunction()->getContext();
-           Ctx.emitError("Ran out of VGPRs for spilling SGPR");
-        }
-
         BuildMI(*MBB, MI, DL,
                 TII->getMCOpcodeFromPseudo(AMDGPU::V_READLANE_B32),
                 SubReg)