[llvm] r300911 - [InstCombine] allow shl+shr demanded bits folds with splat constants

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Apr 20 17:33:54 2017
New Revision: 300911

URL: http://llvm.org/viewvc/llvm-project?rev=300911&view=rev
Log:
[InstCombine] allow shl+shr demanded bits folds with splat constants

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
    llvm/trunk/test/Transforms/InstCombine/shift.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h?rev=300911&r1=300910&r2=300911&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h Thu Apr 20 17:33:54 2017
@@ -551,9 +551,10 @@ private:
                                          unsigned Depth, Instruction *CxtI);
   /// Helper routine of SimplifyDemandedUseBits. It tries to simplify demanded
   /// bit for "r1 = shr x, c1; r2 = shl r1, c2" instruction sequence.
-  Value *SimplifyShrShlDemandedBits(Instruction *Lsr, Instruction *Sftl,
-                                    const APInt &DemandedMask, APInt &KnownZero,
-                                    APInt &KnownOne);
+  Value *SimplifyShrShlDemandedBits(
+      Instruction *Shr, const APInt &ShrOp1, Instruction *Shl,
+      const APInt &ShlOp1, const APInt &DemandedMask, APInt &KnownZero,
+      APInt &KnownOne);
 
   /// \brief Tries to simplify operands to an integer instruction based on its
   /// demanded bits.

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp?rev=300911&r1=300910&r2=300911&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp Thu Apr 20 17:33:54 2017
@@ -472,15 +472,12 @@ Value *InstCombiner::SimplifyDemandedUse
   case Instruction::Shl: {
     const APInt *SA;
     if (match(I->getOperand(1), m_APInt(SA))) {
-      {
-        Value *VarX; ConstantInt *C1;
-        if (match(I->getOperand(0), m_Shr(m_Value(VarX), m_ConstantInt(C1)))) {
-          Instruction *Shr = cast<Instruction>(I->getOperand(0));
-          Value *R = SimplifyShrShlDemandedBits(Shr, I, DemandedMask,
-                                                KnownZero, KnownOne);
-          if (R)
-            return R;
-        }
+      const APInt *ShrAmt;
+      if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt)))) {
+        Instruction *Shr = cast<Instruction>(I->getOperand(0));
+        if (Value *R = SimplifyShrShlDemandedBits(
+                Shr, *ShrAmt, I, *SA, DemandedMask, KnownZero, KnownOne))
+          return R;
       }
 
       uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
@@ -876,20 +873,17 @@ Value *InstCombiner::SimplifyMultipleUse
 ///
 /// As with SimplifyDemandedUseBits, it returns NULL if the simplification was
 /// not successful.
-Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr,
-                                                Instruction *Shl,
-                                                const APInt &DemandedMask,
-                                                APInt &KnownZero,
-                                                APInt &KnownOne) {
-
-  const APInt &ShlOp1 = cast<ConstantInt>(Shl->getOperand(1))->getValue();
-  const APInt &ShrOp1 = cast<ConstantInt>(Shr->getOperand(1))->getValue();
+Value *
+InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr, const APInt &ShrOp1,
+                                         Instruction *Shl, const APInt &ShlOp1,
+                                         const APInt &DemandedMask,
+                                         APInt &KnownZero, APInt &KnownOne) {
   if (!ShlOp1 || !ShrOp1)
-      return nullptr; // Noop.
+    return nullptr; // No-op.
 
   Value *VarX = Shr->getOperand(0);
   Type *Ty = VarX->getType();
-  unsigned BitWidth = Ty->getIntegerBitWidth();
+  unsigned BitWidth = Ty->getScalarSizeInBits();
   if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
     return nullptr; // Undef.
 

Modified: llvm/trunk/test/Transforms/InstCombine/shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/shift.ll?rev=300911&r1=300910&r2=300911&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/shift.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/shift.ll Thu Apr 20 17:33:54 2017
@@ -1075,9 +1075,8 @@ define i32 @test54(i32 %x) {
 
 define <2 x i32> @test54_splat_vec(<2 x i32> %x) {
 ; CHECK-LABEL: @test54_splat_vec(
-; CHECK-NEXT:    [[SHR2:%.*]] = lshr <2 x i32> %x, <i32 1, i32 1>
-; CHECK-NEXT:    [[SHL:%.*]] = shl <2 x i32> [[SHR2]], <i32 4, i32 4>
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i32> [[SHL]], <i32 16, i32 16>
+; CHECK-NEXT:    [[TMP1:%.*]] = shl <2 x i32> %x, <i32 3, i32 3>
+; CHECK-NEXT:    [[AND:%.*]] = and <2 x i32> [[TMP1]], <i32 16, i32 16>
 ; CHECK-NEXT:    ret <2 x i32> [[AND]]
 ;
   %shr2 = lshr <2 x i32> %x, <i32 1, i32 1>
@@ -1138,9 +1137,8 @@ define i32 @test58(i32 %x) {
 
 define <2 x i32> @test58_splat_vec(<2 x i32> %x) {
 ; CHECK-LABEL: @test58_splat_vec(
-; CHECK-NEXT:    [[SHR:%.*]] = ashr <2 x i32> %x, <i32 4, i32 4>
-; CHECK-NEXT:    [[SHL:%.*]] = shl nsw <2 x i32> [[SHR]], <i32 1, i32 1>
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i32> [[SHL]], <i32 1, i32 1>
+; CHECK-NEXT:    [[TMP1:%.*]] = ashr <2 x i32> %x, <i32 3, i32 3>
+; CHECK-NEXT:    [[OR:%.*]] = or <2 x i32> [[TMP1]], <i32 1, i32 1>
 ; CHECK-NEXT:    ret <2 x i32> [[OR]]
 ;
   %shr = ashr <2 x i32> %x, <i32 4, i32 4>