[lanai] Add computeKnownBitsForTargetNode for Lanai.

Summary: computeKnownBitsForTargetNode was not defined for Lanai which resulted in additional AND's with 0x1 for the output of SETCC instructions.

Reviewers: eliben, majnemer

Reviewed By: majnemer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29605

llvm-svn: 302568

lib/Target/Lanai/LanaiISelLowering.cpp

@@ -11,9 +11,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "LanaiISelLowering.h"
 #include "Lanai.h"
 #include "LanaiCondCode.h"
-#include "LanaiISelLowering.h"
 #include "LanaiMachineFunctionInfo.h"
 #include "LanaiSubtarget.h"
 #include "LanaiTargetObjectFile.h"
@@ -38,10 +38,11 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/Support/Casting.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/CodeGen.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/KnownBits.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetCallingConv.h"
@@ -1499,3 +1500,24 @@ SDValue LanaiTargetLowering::PerformDAGCombine(SDNode *N,
 
   return SDValue();
 }
+
+void LanaiTargetLowering::computeKnownBitsForTargetNode(
+    const SDValue Op, KnownBits &Known, const APInt &DemandedElts,
+    const SelectionDAG &DAG, unsigned Depth) const {
+  unsigned BitWidth = Known.getBitWidth();
+  switch (Op.getOpcode()) {
+  default:
+    break;
+  case LanaiISD::SETCC:
+    Known = KnownBits(BitWidth);
+    Known.Zero.setBits(1, BitWidth);
+    break;
+  case LanaiISD::SELECT_CC:
+    KnownBits Known2;
+    DAG.computeKnownBits(Op->getOperand(0), Known, Depth + 1);
+    DAG.computeKnownBits(Op->getOperand(1), Known2, Depth + 1);
+    Known.Zero &= Known2.Zero;
+    Known.One &= Known2.One;
+    break;
+  }
+}

lib/Target/Lanai/LanaiISelLowering.h

@@ -106,6 +106,11 @@ public:
 
   SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
+  void computeKnownBitsForTargetNode(const SDValue Op, KnownBits &Known,
+                                     const APInt &DemandedElts,
+                                     const SelectionDAG &DAG,
+                                     unsigned Depth = 0) const override;
+
 private:
   SDValue LowerCCCCallTo(SDValue Chain, SDValue Callee,
                          CallingConv::ID CallConv, bool IsVarArg,

lib/Target/Lanai/LanaiInstrInfo.td

@@ -771,9 +771,6 @@ let Uses = [SR] in {
                     [(set (i32 GPR:$Rs1), (LanaiSetCC imm:$DDDI))]>;
 }
 
-// SCC's output is already 1-bit so and'ing with 1 is redundant.
-def : Pat<(and (LanaiSetCC imm:$DDDI), 1), (SCC imm:$DDDI)>;
-
 // Select with hardware support
 let Uses = [SR], isSelect = 1 in {
   def SELECT : InstRR<0b111, (outs GPR:$Rd),

test/CodeGen/Lanai/masking_setccs.ll

@@ -0,0 +1,48 @@
+; RUN: llc < %s | FileCheck %s
+
+; Test that unnecessary masking with 0x1 is not inserted.
+
+target datalayout = "E-m:e-p:32:32-i64:64-a:0:32-n32-S64"
+target triple = "lanai"
+
+; CHECK-LABEL: masking:
+; CHECK-NOT: mov 1
+define i32 @masking(i32 inreg %a, i32 inreg %b, i32 inreg %c, i32 inreg %d) {
+entry:
+  %cmp = icmp ne i32 %a, 0
+  %cmp1 = icmp ult i32 %a, %b
+  %or.cond = and i1 %cmp, %cmp1
+  br i1 %or.cond, label %return, label %if.end
+
+if.end:                                           ; preds = %entry
+  %cmp2 = icmp ne i32 %b, 0
+  %cmp4 = icmp ult i32 %b, %c
+  %or.cond29 = and i1 %cmp2, %cmp4
+  br i1 %or.cond29, label %return, label %if.end6
+
+if.end6:                                          ; preds = %if.end
+  %cmp7 = icmp ne i32 %c, 0
+  %cmp9 = icmp ult i32 %c, %d
+  %or.cond30 = and i1 %cmp7, %cmp9
+  br i1 %or.cond30, label %return, label %if.end11
+
+if.end11:                                         ; preds = %if.end6
+  %cmp12 = icmp ne i32 %d, 0
+  %cmp14 = icmp ult i32 %d, %a
+  %or.cond31 = and i1 %cmp12, %cmp14
+  %b. = select i1 %or.cond31, i32 %b, i32 21
+  ret i32 %b.
+
+return:                                           ; preds = %if.end6, %if.end, %entry
+  %retval.0 = phi i32 [ %c, %entry ], [ %d, %if.end ], [ %a, %if.end6 ]
+  ret i32 %retval.0
+}
+
+; CHECK-LABEL: notnot:
+; CHECK-NOT: mov 1
+define i32 @notnot(i32 %x) {
+entry:
+  %tobool = icmp ne i32 %x, 0
+  %lnot.ext = zext i1 %tobool to i32
+  ret i32 %lnot.ext
+}