[llvm] r292238 - [InstCombine] Fold ((C1 OP zext(X)) & C2) -> zext((C1 OP X) & C2)

[David Majnemer via llvm-commits]

Author: majnemer
Date: Tue Jan 17 12:08:06 2017
New Revision: 292238

URL: http://llvm.org/viewvc/llvm-project?rev=292238&view=rev
Log:
[InstCombine] Fold ((C1 OP zext(X)) & C2) -> zext((C1 OP X) & C2)

This further extends r292179 to support additional binary operators
beyond subtraction.

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

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=292238&r1=292237&r2=292238&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Tue Jan 17 12:08:06 2017
@@ -1331,21 +1331,6 @@ Instruction *InstCombiner::visitAnd(Bina
         if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
           return BinaryOperator::CreateAnd(V, AndRHS);
 
-        // ((C1-zext(X)) & C2) -> zext((C1-X) & C2) if C2 fits in the bitwidth
-        // of X.
-        if (auto *ZI = dyn_cast<ZExtInst>(Op0RHS)) {
-          auto *X = ZI->getOperand(0);
-          ConstantInt *C1;
-          if (match(Op0LHS, m_ConstantInt(C1)) &&
-              AndRHSMask.isIntN(X->getType()->getScalarSizeInBits())) {
-            auto *TruncC1 = ConstantExpr::getTrunc(C1, X->getType());
-            auto *Sub = Builder->CreateSub(TruncC1, X);
-            auto *TruncC2 = ConstantExpr::getTrunc(AndRHS, X->getType());
-            auto *And = Builder->CreateAnd(Sub, TruncC2);
-            return new ZExtInst(And, I.getType());
-          }
-        }
-
         // -x & 1 -> x & 1
         if (AndRHSMask == 1 && match(Op0LHS, m_Zero()))
           return BinaryOperator::CreateAnd(Op0RHS, AndRHS);
@@ -1376,6 +1361,34 @@ Instruction *InstCombiner::visitAnd(Bina
         break;
       }
 
+      // ((C1 OP zext(X)) & C2) -> zext((C1-X) & C2) if C2 fits in the bitwidth
+      // of X and OP behaves well when given trunc(C1) and X.
+      switch (Op0I->getOpcode()) {
+      default:
+        break;
+      case Instruction::Xor:
+      case Instruction::Or:
+      case Instruction::Mul:
+      case Instruction::Add:
+      case Instruction::Sub:
+        Value *X;
+        ConstantInt *C1;
+        if (match(Op0I, m_BinOp(m_ZExt(m_Value(X)), m_ConstantInt(C1))) ||
+            match(Op0I, m_BinOp(m_ConstantInt(C1), m_ZExt(m_Value(X))))) {
+          if (AndRHSMask.isIntN(X->getType()->getScalarSizeInBits())) {
+            auto *TruncC1 = ConstantExpr::getTrunc(C1, X->getType());
+            Value *BinOp;
+            if (isa<ZExtInst>(Op0LHS))
+              BinOp = Builder->CreateBinOp(Op0I->getOpcode(), X, TruncC1);
+            else
+              BinOp = Builder->CreateBinOp(Op0I->getOpcode(), TruncC1, X);
+            auto *TruncC2 = ConstantExpr::getTrunc(AndRHS, X->getType());
+            auto *And = Builder->CreateAnd(BinOp, TruncC2);
+            return new ZExtInst(And, I.getType());
+          }
+        }
+      }
+
       if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
         if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
           return Res;

Modified: llvm/trunk/test/Transforms/InstCombine/and.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/and.ll?rev=292238&r1=292237&r2=292238&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/and.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/and.ll Tue Jan 17 12:08:06 2017
@@ -436,3 +436,49 @@ define i64 @test35(i32 %X) {
   %res = and i64 %zsub, 240
   ret i64 %res
 }
+
+define i64 @test36(i32 %X) {
+; CHECK-LABEL: @test36(
+; CHECK-NEXT:  %[[sub:.*]] = add i32 %X, 7
+; CHECK-NEXT:  %[[and:.*]] = and i32 %[[sub]], 240
+; CHECK-NEXT:  %[[cst:.*]] = zext i32 %[[and]] to i64
+; CHECK-NEXT:  ret i64 %[[cst]]
+  %zext = zext i32 %X to i64
+  %zsub = add i64 %zext, 7
+  %res = and i64 %zsub, 240
+  ret i64 %res
+}
+
+define i64 @test37(i32 %X) {
+; CHECK-LABEL: @test37(
+; CHECK-NEXT:  %[[sub:.*]] = mul i32 %X, 7
+; CHECK-NEXT:  %[[and:.*]] = and i32 %[[sub]], 240
+; CHECK-NEXT:  %[[cst:.*]] = zext i32 %[[and]] to i64
+; CHECK-NEXT:  ret i64 %[[cst]]
+  %zext = zext i32 %X to i64
+  %zsub = mul i64 %zext, 7
+  %res = and i64 %zsub, 240
+  ret i64 %res
+}
+
+define i64 @test38(i32 %X) {
+; CHECK-LABEL: @test38(
+; CHECK-NEXT:  %[[and:.*]] = and i32 %X, 240
+; CHECK-NEXT:  %[[cst:.*]] = zext i32 %[[and]] to i64
+; CHECK-NEXT:  ret i64 %[[cst]]
+  %zext = zext i32 %X to i64
+  %zsub = xor i64 %zext, 7
+  %res = and i64 %zsub, 240
+  ret i64 %res
+}
+
+define i64 @test39(i32 %X) {
+; CHECK-LABEL: @test39(
+; CHECK-NEXT:  %[[and:.*]] = and i32 %X, 240
+; CHECK-NEXT:  %[[cst:.*]] = zext i32 %[[and]] to i64
+; CHECK-NEXT:  ret i64 %[[cst]]
+  %zext = zext i32 %X to i64
+  %zsub = or i64 %zext, 7
+  %res = and i64 %zsub, 240
+  ret i64 %res
+}