0077-RISCV-Implement-computeKnownBitsForTargetNode-for-RI.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Alex Bradbury <asb@lowrisc.org>
Subject: [RISCV] Implement computeKnownBitsForTargetNode for
 RISCVISD::SELECT_CC

Doesn't seem to have any real impact on the code I'm testing against.
---
 lib/Target/RISCV/RISCVISelLowering.cpp | 14 ++++++++++++++
 lib/Target/RISCV/RISCVISelLowering.h   |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/lib/Target/RISCV/RISCVISelLowering.cpp b/lib/Target/RISCV/RISCVISelLowering.cpp
index adf0d0c70ab..bac74ee62c5 100644
--- a/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -30,6 +30,7 @@
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/KnownBits.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
@@ -215,6 +216,19 @@ bool RISCVTargetLowering::isZExtFree(SDValue Val, EVT VT2) const {
   return TargetLowering::isZExtFree(Val, VT2);
 }
 
+void RISCVTargetLowering::computeKnownBitsForTargetNode(
+    const SDValue Op, KnownBits &Known, const APInt &DemandedElts,
+    const SelectionDAG &DAG, unsigned Depth) const {
+  if (Op.getOpcode() != RISCVISD::SELECT_CC)
+    return;
+
+  KnownBits Known2;
+  DAG.computeKnownBits(Op->getOperand(3), Known, Depth + 1);
+  DAG.computeKnownBits(Op->getOperand(4), Known2, Depth + 1);
+  Known.Zero &= Known2.Zero;
+  Known.One &= Known2.One;
+}
+
 // Changes the condition code and swaps operands if necessary, so the SetCC
 // operation matches one of the comparisons supported directly in the RISC-V
 // ISA.
diff --git a/lib/Target/RISCV/RISCVISelLowering.h b/lib/Target/RISCV/RISCVISelLowering.h
index ccce434f69f..807cb9c0b8d 100644
--- a/lib/Target/RISCV/RISCVISelLowering.h
+++ b/lib/Target/RISCV/RISCVISelLowering.h
@@ -46,6 +46,11 @@ public:
   bool isTruncateFree(EVT SrcVT, EVT DstVT) const override;
   bool isZExtFree(SDValue Val, EVT VT2) const override;
 
+  void computeKnownBitsForTargetNode(const SDValue Op, KnownBits &Known,
+                                     const APInt &DemandedElts,
+                                     const SelectionDAG &DAG,
+                                     unsigned Depth = 0) const override;
+
   // Provide custom lowering hooks for some operations.
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
 
-- 
2.16.2