RegBankSelect: Fix copy insertion point for terminators

If a copy was needed to handle the condition of brcond, it was being
inserted before the defining instruction. Add tests for iterator edge
cases.

I find the existing code here suspect for the case where it's looking
for terminators that modify the register. It's going to insert a copy
in the middle of the terminators, which isn't allowed (it might be
necessary to have a COPY_terminator if anybody actually needs this).

Also legalize brcond for AMDGPU.

llvm-svn: 350595

3 files changed, 43 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
index 98df7d34857..bfd7a68a8b0 100644
--- a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
@@ -717,15 +717,21 @@ RegBankSelect::RepairingPlacement::RepairingPlacement(
     unsigned Reg = MO.getReg();
     if (Before) {
       // Check whether Reg is defined by any terminator.
-      MachineBasicBlock::iterator It = MI;
-      for (auto Begin = MI.getParent()->begin();
-           --It != Begin && It->isTerminator();)
-        if (It->modifiesRegister(Reg, &TRI)) {
-          // Insert the repairing code right after the definition.
-          addInsertPoint(*It, /*Before*/ false);
-          return;
-        }
-      addInsertPoint(*It, /*Before*/ true);
+      MachineBasicBlock::reverse_iterator It = MI;
+      auto REnd = MI.getParent()->rend();
+
+      for (; It != REnd && It->isTerminator(); ++It) {
+        assert(!It->modifiesRegister(Reg, &TRI) &&
+               "copy insertion in middle of terminators not handled");
+      }
+
+      if (It == REnd) {
+        addInsertPoint(*MI.getParent()->begin(), true);
+        return;
+      }
+
+      // We are sure to be right before the first terminator.
+      addInsertPoint(*It, /*Before*/ false);
       return;
     }
     // Make sure Reg is not redefined by other terminators, otherwise
diff --git a/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
index 820ff4b6add..01ee4afe886 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
@@ -85,6 +85,8 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST,
     PrivatePtr
   };
 
+  setAction({G_BRCOND, S1}, Legal);
+
   setAction({G_ADD, S32}, Legal);
   setAction({G_ASHR, S32}, Legal);
   setAction({G_SUB, S32}, Legal);
diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
index 9d576e62160..90553425c95 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
@@ -221,6 +221,22 @@ AMDGPURegisterBankInfo::getInstrAlternativeMappings(
     AltMappings.push_back(&VVMapping);
     return AltMappings;
   }
+  case AMDGPU::G_BRCOND: {
+    assert(MRI.getType(MI.getOperand(0).getReg()).getSizeInBits() == 1);
+
+    const InstructionMapping &SMapping = getInstructionMapping(
+      1, 1, getOperandsMapping(
+        {AMDGPU::getValueMapping(AMDGPU::SCCRegBankID, 1), nullptr}),
+      2); // Num Operands
+    AltMappings.push_back(&SMapping);
+
+    const InstructionMapping &VMapping = getInstructionMapping(
+      1, 1, getOperandsMapping(
+        {AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, 1), nullptr }),
+      2); // Num Operands
+    AltMappings.push_back(&VMapping);
+    return AltMappings;
+  }
   default:
     break;
   }
@@ -712,6 +728,16 @@ AMDGPURegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   case AMDGPU::G_ATOMIC_CMPXCHG: {
     return getDefaultMappingAllVGPR(MI);
   }
+  case AMDGPU::G_BRCOND: {
+    unsigned Bank = getRegBankID(MI.getOperand(0).getReg(), MRI, *TRI,
+                                 AMDGPU::SGPRRegBankID);
+    assert(MRI.getType(MI.getOperand(0).getReg()).getSizeInBits() == 1);
+    if (Bank != AMDGPU::SCCRegBankID)
+      Bank = AMDGPU::SGPRRegBankID;
+
+    OpdsMapping[0] = AMDGPU::getValueMapping(Bank, 1);
+    break;
+  }
   }
 
   return getInstructionMapping(1, 1, getOperandsMapping(OpdsMapping),