R600/SI: Special case v_mov_b32 as really rematerializable

This should be fixed to properly understand all rematerializable
instructions while ignoring implicit reads of exec.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235671 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/R600/SIInstrInfo.cpp

@@ -74,6 +74,20 @@ static bool nodesHaveSameOperandValue(SDNode *N0, SDNode* N1, unsigned OpName) {
   return N0->getOperand(Op0Idx) == N1->getOperand(Op1Idx);
 }
 
+bool SIInstrInfo::isReallyTriviallyReMaterializable(const MachineInstr *MI,
+                                                    AliasAnalysis *AA) const {
+  // TODO: The generic check fails for VALU instructions that should be
+  // rematerializable due to implicit reads of exec. We really want all of the
+  // generic logic for this except for this.
+  switch (MI->getOpcode()) {
+  case AMDGPU::V_MOV_B32_e32:
+  case AMDGPU::V_MOV_B32_e64:
+    return true;
+  default:
+    return false;
+  }
+}
+
 bool SIInstrInfo::areLoadsFromSameBasePtr(SDNode *Load0, SDNode *Load1,
                                           int64_t &Offset0,
                                           int64_t &Offset1) const {

lib/Target/R600/SIInstrInfo.h

@@ -72,6 +72,9 @@ public:
     return RI;
   }
 
+  bool isReallyTriviallyReMaterializable(const MachineInstr *MI,
+                                         AliasAnalysis *AA) const override;
+
   bool areLoadsFromSameBasePtr(SDNode *Load1, SDNode *Load2,
                                int64_t &Offset1,
                                int64_t &Offset2) const override;