AMDGPU/GlobalISel: Allow scalar s1 and/or/xor

If a 1-bit value is in a 32-bit VGPR, the scalar opcodes set SCC to
whether the result is 0. If the inputs are SCC, these can be copied to
a 32-bit SGPR to produce an SCC result.

llvm-svn: 366125

1 files changed, 91 insertions, 6 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
index be05d9cb0ec..815cbc5e26e 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
@@ -108,14 +108,22 @@ AMDGPURegisterBankInfo::AMDGPURegisterBankInfo(const TargetRegisterInfo &TRI)
 unsigned AMDGPURegisterBankInfo::copyCost(const RegisterBank &Dst,
                                           const RegisterBank &Src,
                                           unsigned Size) const {
+  // TODO: Should there be a UniformVGPRRegBank which can use readfirstlane?
   if (Dst.getID() == AMDGPU::SGPRRegBankID &&
       Src.getID() == AMDGPU::VGPRRegBankID) {
     return std::numeric_limits<unsigned>::max();
   }
 
-  // SGPRRegBank with size 1 is actually vcc or another 64-bit sgpr written by
-  // the valu.
-  if (Size == 1 && Dst.getID() == AMDGPU::SCCRegBankID &&
+  // Bool values are tricky, because the meaning is based on context. The SCC
+  // and VCC banks are for the natural scalar and vector conditions produced by
+  // a compare.
+  //
+  // Legalization doesn't know about the necessary context, so an s1 use may
+  // have been a truncate from an arbitrary value, in which case a copy (lowered
+  // as a compare with 0) needs to be inserted.
+  if (Size == 1 &&
+      (Dst.getID() == AMDGPU::SCCRegBankID ||
+       Dst.getID() == AMDGPU::SGPRRegBankID) &&
       (Src.getID() == AMDGPU::SGPRRegBankID ||
        Src.getID() == AMDGPU::VGPRRegBankID ||
        Src.getID() == AMDGPU::VCCRegBankID))
@@ -333,6 +341,35 @@ AMDGPURegisterBankInfo::getInstrAlternativeMappings(
   case TargetOpcode::G_OR:
   case TargetOpcode::G_XOR: {
     unsigned Size = getSizeInBits(MI.getOperand(0).getReg(), MRI, *TRI);
+
+    if (Size == 1) {
+      // s_{and|or|xor}_b32 set scc when the result of the 32-bit op is not 0.
+      const InstructionMapping &SCCMapping = getInstructionMapping(
+        1, 1, getOperandsMapping(
+          {AMDGPU::getValueMapping(AMDGPU::SCCRegBankID, Size),
+           AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, Size),
+           AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, Size)}),
+        3); // Num Operands
+      AltMappings.push_back(&SCCMapping);
+
+      const InstructionMapping &SGPRMapping = getInstructionMapping(
+        1, 1, getOperandsMapping(
+          {AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, Size),
+           AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, Size),
+           AMDGPU::getValueMapping(AMDGPU::SGPRRegBankID, Size)}),
+        3); // Num Operands
+      AltMappings.push_back(&SGPRMapping);
+
+      const InstructionMapping &VCCMapping0 = getInstructionMapping(
+        2, 10, getOperandsMapping(
+          {AMDGPU::getValueMapping(AMDGPU::VCCRegBankID, Size),
+              AMDGPU::getValueMapping(AMDGPU::VCCRegBankID, Size),
+              AMDGPU::getValueMapping(AMDGPU::VCCRegBankID, Size)}),
+        3); // Num Operands
+      AltMappings.push_back(&VCCMapping0);
+      return AltMappings;
+    }
+
     if (Size != 64)
       break;
 
@@ -360,7 +397,7 @@ AMDGPURegisterBankInfo::getInstrAlternativeMappings(
       3); // Num Operands
     AltMappings.push_back(&SVMapping);
 
-    // SGPR in LHS is slightly preferrable, so make it VS more expnesive than
+    // SGPR in LHS is slightly preferrable, so make it VS more expensive than
     // SV.
     const InstructionMapping &VSMapping = getInstructionMapping(
       3, 4, getOperandsMapping(
@@ -1551,8 +1588,56 @@ AMDGPURegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   case AMDGPU::G_XOR: {
     unsigned Size = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
     if (Size == 1) {
-      OpdsMapping[0] = OpdsMapping[1] =
-        OpdsMapping[2] = AMDGPU::getValueMapping(AMDGPU::VCCRegBankID, Size);
+      const RegisterBank *DstBank
+        = getRegBank(MI.getOperand(0).getReg(), MRI, *TRI);
+
+      unsigned TargetBankID = -1;
+      unsigned BankLHS = -1;
+      unsigned BankRHS = -1;
+      if (DstBank) {
+        TargetBankID = DstBank->getID();
+        if (DstBank == &AMDGPU::VCCRegBank) {
+          TargetBankID = AMDGPU::VCCRegBankID;
+          BankLHS = AMDGPU::VCCRegBankID;
+          BankRHS = AMDGPU::VCCRegBankID;
+        } else if (DstBank == &AMDGPU::SCCRegBank) {
+          TargetBankID = AMDGPU::SCCRegBankID;
+          BankLHS = AMDGPU::SGPRRegBankID;
+          BankRHS = AMDGPU::SGPRRegBankID;
+        } else {
+          BankLHS = getRegBankID(MI.getOperand(1).getReg(), MRI, *TRI,
+                                 AMDGPU::SGPRRegBankID);
+          BankRHS = getRegBankID(MI.getOperand(2).getReg(), MRI, *TRI,
+                                 AMDGPU::SGPRRegBankID);
+        }
+      } else {
+        BankLHS = getRegBankID(MI.getOperand(1).getReg(), MRI, *TRI,
+                               AMDGPU::VCCRegBankID);
+        BankRHS = getRegBankID(MI.getOperand(2).getReg(), MRI, *TRI,
+                               AMDGPU::VCCRegBankID);
+
+        // Both inputs should be true booleans to produce a boolean result.
+        if (BankLHS == AMDGPU::VGPRRegBankID || BankRHS == AMDGPU::VGPRRegBankID) {
+          TargetBankID = AMDGPU::VGPRRegBankID;
+        } else if (BankLHS == AMDGPU::VCCRegBankID || BankRHS == AMDGPU::VCCRegBankID) {
+          TargetBankID = AMDGPU::VCCRegBankID;
+          BankLHS = AMDGPU::VCCRegBankID;
+          BankRHS = AMDGPU::VCCRegBankID;
+        } else if (BankLHS == AMDGPU::SGPRRegBankID && BankRHS == AMDGPU::SGPRRegBankID) {
+          TargetBankID = AMDGPU::SGPRRegBankID;
+        } else if (BankLHS == AMDGPU::SCCRegBankID || BankRHS == AMDGPU::SCCRegBankID) {
+          // The operation must be done on a 32-bit register, but it will set
+          // scc. The result type could interchangably be SCC or SGPR, since
+          // both values will be produced.
+          TargetBankID = AMDGPU::SCCRegBankID;
+          BankLHS = AMDGPU::SGPRRegBankID;
+          BankRHS = AMDGPU::SGPRRegBankID;
+        }
+      }
+
+      OpdsMapping[0] = AMDGPU::getValueMapping(TargetBankID, Size);
+      OpdsMapping[1] = AMDGPU::getValueMapping(BankLHS, Size);
+      OpdsMapping[2] = AMDGPU::getValueMapping(BankRHS, Size);
       break;
     }