[llvm] r216135 - New InstCombine pattern: (icmp ult/ule (A + C1), C3) | (icmp ult/ule (A + C2), C3) to (icmp ult/ule ((A & ~(C1 ^ C2)) + max(C1, C2)), C3) under certain condition

[Yi Jiang]

Author: yjiang
Date: Wed Aug 20 17:55:40 2014
New Revision: 216135

URL: http://llvm.org/viewvc/llvm-project?rev=216135&view=rev
Log:
New InstCombine pattern: (icmp ult/ule (A + C1), C3) | (icmp ult/ule (A + C2), C3)  to (icmp ult/ule ((A & ~(C1 ^ C2)) + max(C1, C2)), C3) under certain condition

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

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=216135&r1=216134&r2=216135&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Wed Aug 20 17:55:40 2014
@@ -1612,6 +1612,61 @@ Value *InstCombiner::FoldOrOfICmps(ICmpI
     }
   }
 
+  // Fold (icmp ult/ule (A + C1), C3) | (icmp ult/ule (A + C2), C3)
+  //                   -->  (icmp ult/ule ((A & ~(C1 ^ C2)) + max(C1, C2)), C3)
+  // The original condition actually refers to the following two ranges:
+  // [MAX_UINT-C1+1, MAX_UINT-C1+1+C3] and [MAX_UINT-C2+1, MAX_UINT-C2+1+C3]
+  // We can fold these two ranges if:
+  // 1) C1 and C2 is unsigned greater than C3.
+  // 2) The two ranges are separated.
+  // 3) C1 ^ C2 is one-bit mask.
+  // 4) LowRange1 ^ LowRange2 and HighRange1 ^ HighRange2 are one-bit mask.
+  // This implies all values in the two ranges differ by exactly one bit.
+
+  if ((LHSCC == ICmpInst::ICMP_ULT || LHSCC == ICmpInst::ICMP_ULE) &&
+      LHSCC == RHSCC && LHSCst && RHSCst && LHS->hasOneUse() &&
+      RHS->hasOneUse() && LHSCst->getType() == RHSCst->getType() &&
+      LHSCst->getValue() == (RHSCst->getValue())) {
+
+    Value *LAdd = LHS->getOperand(0);
+    Value *RAdd = RHS->getOperand(0);
+
+    Value *LAddOpnd, *RAddOpnd;
+    ConstantInt *LAddCst, *RAddCst;
+    if (match(LAdd, m_Add(m_Value(LAddOpnd), m_ConstantInt(LAddCst))) &&
+        match(RAdd, m_Add(m_Value(RAddOpnd), m_ConstantInt(RAddCst))) &&
+        LAddCst->getValue().ugt(LHSCst->getValue()) &&
+        RAddCst->getValue().ugt(LHSCst->getValue())) {
+
+      APInt DiffCst = LAddCst->getValue() ^ RAddCst->getValue();
+      if (LAddOpnd == RAddOpnd && DiffCst.isPowerOf2()) {
+        ConstantInt *MaxAddCst = nullptr;
+        if (LAddCst->getValue().ult(RAddCst->getValue()))
+          MaxAddCst = RAddCst;
+        else
+          MaxAddCst = LAddCst;
+
+        APInt RRangeLow = -RAddCst->getValue();
+        APInt RRangeHigh = RRangeLow + LHSCst->getValue();
+        APInt LRangeLow = -LAddCst->getValue();
+        APInt LRangeHigh = LRangeLow + LHSCst->getValue();
+        APInt LowRangeDiff = RRangeLow ^ LRangeLow;
+        APInt HighRangeDiff = RRangeHigh ^ LRangeHigh;
+        APInt RangeDiff = LRangeLow.sgt(RRangeLow) ? LRangeLow - RRangeLow
+                                                   : RRangeLow - LRangeLow;
+
+        if (LowRangeDiff.isPowerOf2() && LowRangeDiff == HighRangeDiff &&
+            RangeDiff.ugt(LHSCst->getValue())) {
+          Value *MaskCst = ConstantInt::get(LAddCst->getType(), ~DiffCst);
+
+          Value *NewAnd = Builder->CreateAnd(LAddOpnd, MaskCst);
+          Value *NewAdd = Builder->CreateAdd(NewAnd, MaxAddCst);
+          return (Builder->CreateICmp(LHS->getPredicate(), NewAdd, LHSCst));
+        }
+      }
+    }
+  }
+
   // (icmp1 A, B) | (icmp2 A, B) --> (icmp3 A, B)
   if (PredicatesFoldable(LHSCC, RHSCC)) {
     if (LHS->getOperand(0) == RHS->getOperand(1) &&

Modified: llvm/trunk/test/Transforms/InstCombine/or.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/or.ll?rev=216135&r1=216134&r2=216135&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/or.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/or.ll Wed Aug 20 17:55:40 2014
@@ -480,3 +480,29 @@ define i32 @test45(i32 %x, i32 %y, i32 %
   %or1 = or i32 %and, %y
   ret i32 %or1
 }
+
+define i1 @test46(i8 signext %c)  {
+  %c.off = add i8 %c, -97
+  %cmp1 = icmp ult i8 %c.off, 26
+  %c.off17 = add i8 %c, -65
+  %cmp2 = icmp ult i8 %c.off17, 26
+  %or = or i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK-LABEL: @test46(
+; CHECK-NEXT:  and i8 %c, -33
+; CHECK-NEXT:  add i8 %1, -65
+; CHECK-NEXT:  icmp ult i8 %2, 26
+}
+
+define i1 @test47(i8 signext %c)  {
+  %c.off = add i8 %c, -65
+  %cmp1 = icmp ule i8 %c.off, 26
+  %c.off17 = add i8 %c, -97
+  %cmp2 = icmp ule i8 %c.off17, 26
+  %or = or i1 %cmp1, %cmp2
+  ret i1 %or
+; CHECK-LABEL: @test47(
+; CHECK-NEXT:  and i8 %c, -33
+; CHECK-NEXT:  add i8 %1, -65
+; CHECK-NEXT:  icmp ult i8 %2, 27
+}