[llvm] [AMDGPU][GISel] Fold 'min(min(x,y),z)' and 'max(max(x,y),z)' into min3 and max3 (PR #200410)

[Petar Avramovic via llvm-commits]

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@@ -481,6 +491,75 @@ bool AMDGPURegBankCombinerImpl::combineD16Load(MachineInstr &MI) const {
   return false;
 }
 
+void AMDGPURegBankCombinerImpl::applyMinMaxToMinMax3(
+    MachineInstr &MI, MinMaxToMinMax3MatchInfo &MatchInfo) const {
+  B.buildInstr(MatchInfo.Opc, {MI.getOperand(0)},
+               {MatchInfo.Val0, MatchInfo.Val1, MatchInfo.Val2}, MI.getFlags());
+  MI.eraseFromParent();
+  return;
+}
+
+// min(min(a, b), c) == min(a, min(b, c)) == min3(a, b, c)
+// supported scalar type: S32 S16 U32 U16 F32 F16
+bool AMDGPURegBankCombinerImpl::matchMinMaxToMinMax3(
+    MachineInstr &MI, MinMaxToMinMax3MatchInfo &MatchInfo) const {
+  Register Dst = MI.getOperand(0).getReg();
+  Register Src1 = MI.getOperand(1).getReg();
+  Register Src2 = MI.getOperand(2).getReg();
+  // If the register is SGPR, don't optimize it.
+  if (!(isVgprRegBank(Dst) && isVgprRegBank(Src1) && isVgprRegBank(Src2))) {
+    return false;
+  }
+
+  LLT Ty = MRI.getType(Dst);
+  unsigned Opc = MI.getOpcode();
+  bool IsSupportedTy =
+      Ty == LLT::scalar(32) || (Ty == LLT::scalar(16) && STI.hasMin3Max3_16());
+  if (!IsSupportedTy)
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petar-avramovic wrote:

inline IsSupportedTy into if

https://github.com/llvm/llvm-project/pull/200410