[GlobalISel]: Add a getConstantIntVRegVal utility

Returns ConstantInt from G_CONSTANT instruction given its def register.

Differential Revision: https://reviews.llvm.org/D99733

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
index 1a592b6..5bb36ad 100644 (file)
--- a/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/Utils.h
@@ -41,6 +41,7 @@ class TargetLowering;
 class TargetPassConfig;
 class TargetRegisterInfo;
 class TargetRegisterClass;
+class ConstantInt;
 class ConstantFP;
 class APFloat;
 
@@ -189,6 +190,8 @@ getConstantVRegValWithLookThrough(Register VReg, const MachineRegisterInfo &MRI,
                                   bool LookThroughInstrs = true,
                                   bool HandleFConstants = true,
                                   bool LookThroughAnyExt = false);
+const ConstantInt *getConstantIntVRegVal(Register VReg,
+                                         const MachineRegisterInfo &MRI);
 const ConstantFP* getConstantFPVRegVal(Register VReg,
                                        const MachineRegisterInfo &MRI);
 

diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index 0b89ae4..b8dc131 100644 (file)
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -365,6 +365,14 @@ Optional<ValueAndVReg> llvm::getConstantVRegValWithLookThrough(
   return ValueAndVReg{Val, VReg};
 }
 
+const ConstantInt *llvm::getConstantIntVRegVal(Register VReg,
+                                               const MachineRegisterInfo &MRI) {
+  MachineInstr *MI = MRI.getVRegDef(VReg);
+  if (MI->getOpcode() != TargetOpcode::G_CONSTANT)
+    return nullptr;
+  return MI->getOperand(1).getCImm();
+}
+
 const ConstantFP *
 llvm::getConstantFPVRegVal(Register VReg, const MachineRegisterInfo &MRI) {
   MachineInstr *MI = MRI.getVRegDef(VReg);