[SCCP] Remove masking operations

Author: dtcxzyw

llvm/lib/Transforms/Utils/SCCPSolver.cpp

@@ -20,6 +20,7 @@
 #include "llvm/Analysis/ValueLatticeUtils.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -30,6 +31,7 @@
 #include <vector>
 
 using namespace llvm;
+using namespace PatternMatch;
 
 #define DEBUG_TYPE "sccp"
 
@@ -86,7 +88,7 @@ bool SCCPSolver::tryToReplaceWithConstant(Value *V) {
 /// Try to use \p Inst's value range from \p Solver to infer the NUW flag.
 static bool refineInstruction(SCCPSolver &Solver,
                               const SmallPtrSetImpl<Value *> &InsertedValues,
-                              Instruction &Inst) {
+                              Instruction &Inst, Statistic &InstRemovedStat) {
   bool Changed = false;
   auto GetRange = [&Solver, &InsertedValues](Value *Op) {
     if (auto *Const = dyn_cast<Constant>(Op))
@@ -99,6 +101,9 @@ static bool refineInstruction(SCCPSolver &Solver,
         Op->getType(), /*UndefAllowed=*/false);
   };
 
+  Value *X;
+  const APInt *RHSC;
+
   if (isa<OverflowingBinaryOperator>(Inst)) {
     if (Inst.hasNoSignedWrap() && Inst.hasNoUnsignedWrap())
       return false;
@@ -157,6 +162,15 @@ static bool refineInstruction(SCCPSolver &Solver,
                           GEPNoWrapFlags::noUnsignedWrap());
       Changed = true;
     }
+  } else if (match(&Inst, m_And(m_Value(X), m_LowBitMask(RHSC)))) {
+    ConstantRange LRange = GetRange(Inst.getOperand(0));
+    if (!LRange.getUnsignedMax().ule(*RHSC))
+      return false;
+
+    Inst.replaceAllUsesWith(X);
+    Inst.eraseFromParent();
+    ++InstRemovedStat;
+    Changed = true;
   }
 
   return Changed;
@@ -249,7 +263,8 @@ bool SCCPSolver::simplifyInstsInBlock(BasicBlock &BB,
     } else if (replaceSignedInst(*this, InsertedValues, Inst)) {
       MadeChanges = true;
       ++InstReplacedStat;
-    } else if (refineInstruction(*this, InsertedValues, Inst)) {
+    } else if (refineInstruction(*this, InsertedValues, Inst,
+                                 InstRemovedStat)) {
       MadeChanges = true;
     }
   }

llvm/test/Transforms/SCCP/conditions-ranges-with-undef.ll

@@ -46,8 +46,7 @@ define void @val_undef_range() {
 ; CHECK-NEXT:    br i1 [[BC_1]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       true:
 ; CHECK-NEXT:    call void @use(i1 false)
-; CHECK-NEXT:    [[A_127:%.*]] = and i32 [[A]], 127
-; CHECK-NEXT:    call void @use.i32(i32 [[A_127]])
+; CHECK-NEXT:    call void @use.i32(i32 [[A]])
 ; CHECK-NEXT:    ret void
 ; CHECK:       false:
 ; CHECK-NEXT:    ret void
@@ -82,8 +81,7 @@ define void @val_singlecrfromundef_range(i1 %cond) {
 ; CHECK-NEXT:    br label [[TRUE:%.*]]
 ; CHECK:       true:
 ; CHECK-NEXT:    call void @use(i1 false)
-; CHECK-NEXT:    [[P_127:%.*]] = and i32 10, 127
-; CHECK-NEXT:    call void @use.i32(i32 [[P_127]])
+; CHECK-NEXT:    call void @use.i32(i32 10)
 ; CHECK-NEXT:    ret void
 ;
 entry:
@@ -131,8 +129,7 @@ define void @val_undef_to_cr_to_overdef_range(i32 %a, i1 %cond) {
 ; CHECK-NEXT:    br i1 [[BC_1]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       true:
 ; CHECK-NEXT:    call void @use(i1 false)
-; CHECK-NEXT:    [[P_127:%.*]] = and i32 [[P]], 127
-; CHECK-NEXT:    call void @use.i32(i32 [[P_127]])
+; CHECK-NEXT:    call void @use.i32(i32 [[P]])
 ; CHECK-NEXT:    ret void
 ; CHECK:       false:
 ; CHECK-NEXT:    ret void

llvm/test/Transforms/SCCP/range-and.ll

@@ -1,4 +1,4 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --verbose
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S -passes=sccp %s | FileCheck %s
 
 declare void @use(i1)
@@ -140,9 +140,8 @@ define i64 @constant_range_and_255_100(i1 %cond, i64 %a) {
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[P:%.*]] = phi i64 [ [[R_1]], [[BB1]] ], [ [[R_2]], [[BB2]] ]
-; CHECK-NEXT:    [[P_AND:%.*]] = and i64 [[P]], 255
 ; CHECK-NEXT:    call void @use(i1 true)
-; CHECK-NEXT:    ret i64 [[P_AND]]
+; CHECK-NEXT:    ret i64 [[P]]
 ;
 entry:
   br i1 %cond, label %bb1, label %bb2

llvm/test/Transforms/SCCP/range-with-undef.ll

@@ -12,8 +12,7 @@ define i8 @test_binop(i1 %cond, i8 %a) {
 ; CHECK-NEXT:    [[A_EXT:%.*]] = zext i8 [[A]] to i16
 ; CHECK-NEXT:    br label %[[JOIN]]
 ; CHECK:       [[JOIN]]:
-; CHECK-NEXT:    [[PHI:%.*]] = phi i16 [ undef, %[[ENTRY]] ], [ [[A_EXT]], %[[IF]] ]
-; CHECK-NEXT:    [[AND:%.*]] = and i16 [[PHI]], -1
+; CHECK-NEXT:    [[AND:%.*]] = phi i16 [ undef, %[[ENTRY]] ], [ [[A_EXT]], %[[IF]] ]
 ; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i16 [[AND]] to i8
 ; CHECK-NEXT:    ret i8 [[TRUNC]]
 ;