[llvm] r294628 - [InstCombine] use m_APInt to allow demanded bits analysis on splat constants

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Feb  9 15:43:06 2017
New Revision: 294628

URL: http://llvm.org/viewvc/llvm-project?rev=294628&view=rev
Log:
[InstCombine] use m_APInt to allow demanded bits analysis on splat constants

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
    llvm/trunk/test/Transforms/InstCombine/and.ll
    llvm/trunk/test/Transforms/InstCombine/zext.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp?rev=294628&r1=294627&r2=294628&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp Thu Feb  9 15:43:06 2017
@@ -30,18 +30,20 @@ static bool ShrinkDemandedConstant(Instr
   assert(I && "No instruction?");
   assert(OpNo < I->getNumOperands() && "Operand index too large");
 
-  // If the operand is not a constant integer, nothing to do.
-  ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
-  if (!OpC) return false;
+  // The operand must be a constant integer or splat integer.
+  Value *Op = I->getOperand(OpNo);
+  const APInt *C;
+  if (!match(Op, m_APInt(C)))
+    return false;
 
   // If there are no bits set that aren't demanded, nothing to do.
-  Demanded = Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
-  if ((~Demanded & OpC->getValue()) == 0)
+  Demanded = Demanded.zextOrTrunc(C->getBitWidth());
+  if ((~Demanded & *C) == 0)
     return false;
 
   // This instruction is producing bits that are not demanded. Shrink the RHS.
-  Demanded &= OpC->getValue();
-  I->setOperand(OpNo, ConstantInt::get(OpC->getType(), Demanded));
+  Demanded &= *C;
+  I->setOperand(OpNo, ConstantInt::get(Op->getType(), Demanded));
 
   return true;
 }
@@ -114,9 +116,10 @@ Value *InstCombiner::SimplifyDemandedUse
       KnownOne.getBitWidth() == BitWidth &&
       "Value *V, DemandedMask, KnownZero and KnownOne "
       "must have same BitWidth");
-  if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
-    // We know all of the bits for a constant!
-    KnownOne = CI->getValue() & DemandedMask;
+  const APInt *C;
+  if (match(V, m_APInt(C))) {
+    // We know all of the bits for a scalar constant or a splat vector constant!
+    KnownOne = *C & DemandedMask;
     KnownZero = ~KnownOne & DemandedMask;
     return nullptr;
   }

Modified: llvm/trunk/test/Transforms/InstCombine/and.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/and.ll?rev=294628&r1=294627&r2=294628&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/and.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/and.ll Thu Feb  9 15:43:06 2017
@@ -382,12 +382,11 @@ define i32 @test31(i1 %X) {
   ret i32 %A
 }
 
-; FIXME: Demanded bit analysis allows us to eliminate the add.
+; Demanded bit analysis allows us to eliminate the add.
 
 define <2 x i32> @and_demanded_bits_splat_vec(<2 x i32> %x) {
 ; CHECK-LABEL: @and_demanded_bits_splat_vec(
-; CHECK-NEXT:    [[Y:%.*]] = add <2 x i32> %x, <i32 8, i32 8>
-; CHECK-NEXT:    [[Z:%.*]] = and <2 x i32> [[Y]], <i32 7, i32 7>
+; CHECK-NEXT:    [[Z:%.*]] = and <2 x i32> %x, <i32 7, i32 7>
 ; CHECK-NEXT:    ret <2 x i32> [[Z]]
 ;
   %y = add <2 x i32> %x, <i32 8, i32 8>

Modified: llvm/trunk/test/Transforms/InstCombine/zext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/zext.ll?rev=294628&r1=294627&r2=294628&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/zext.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/zext.ll Thu Feb  9 15:43:06 2017
@@ -35,7 +35,7 @@ define <2 x i64> @test3(<2 x i64> %A) {
 
 define <2 x i64> @test4(<2 x i64> %A) {
 ; CHECK-LABEL: @test4(
-; CHECK-NEXT:    [[TMP1:%.*]] = xor <2 x i64> %A, <i64 4294967295, i64 4294967295>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <2 x i64> %A, <i64 63, i64 63>
 ; CHECK-NEXT:    [[XOR:%.*]] = and <2 x i64> [[TMP1]], <i64 23, i64 42>
 ; CHECK-NEXT:    ret <2 x i64> [[XOR]]
 ;