[llvm] [GlobalIsel] Transform build_vector(binop(_, C), ...) -> binop(bv, constant bv) (PR #73577)

[Matt Arsenault via llvm-commits]

Thorsten =?utf-8?q?Schütt?= <schuett at gmail.com>,
Thorsten =?utf-8?q?Schütt?= <schuett at gmail.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/73577 at github.com>


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@@ -6224,3 +6224,89 @@ void CombinerHelper::applyCommuteBinOpOperands(MachineInstr &MI) {
   MI.getOperand(2).setReg(LHSReg);
   Observer.changedInstr(MI);
 }
+
+// Transform build_vector of binop(_,C) -> binop(BV, constant BV).
+bool CombinerHelper::matchBuildVectorToBinOp(MachineInstr &MI,
+                                             BuildFnTy &MatchInfo) {
+  GBuildVector *BuildVector = cast<GBuildVector>(&MI);
+  Register Dst = BuildVector->getReg(0);
+
+  unsigned NumOfSources = BuildVector->getNumSources();
+  if (NumOfSources == 1)
+    return false;
+
+  LLT ElementTy = MRI.getType(BuildVector->getSourceReg(0));
+  LLT BVTy = MRI.getType(BuildVector->getReg(0));
+
+  MachineInstr *FirstDef = MRI.getVRegDef(BuildVector->getSourceReg(0));
+  const unsigned Opcode = FirstDef->getOpcode();
+  SmallVector<Register> LHS;
+
+  if (isa<GIntBinOp>(FirstDef)) {
+    SmallVector<APInt> RHS;
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arsenm wrote:

We probably should have a form that returns a Constant* and also handles G_FCONSTANT (or we could just do away with G_FCONSTANT and always encode as an integer)

https://github.com/llvm/llvm-project/pull/73577