[llvm] r372491 - [InstSimplify] simplifyUnsignedRangeCheck(): X >= Y && Y == 0 --> Y == 0

[Roman Lebedev via llvm-commits]

Author: lebedevri
Date: Sat Sep 21 15:27:39 2019
New Revision: 372491

URL: http://llvm.org/viewvc/llvm-project?rev=372491&view=rev
Log:
[InstSimplify] simplifyUnsignedRangeCheck(): X >= Y && Y == 0  -->  Y == 0

https://rise4fun.com/Alive/v9Y4

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/unsigned-range-checks.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=372491&r1=372490&r2=372491&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Sat Sep 21 15:27:39 2019
@@ -1443,11 +1443,10 @@ static Value *simplifyUnsignedRangeCheck
       isKnownNonZero(X, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
     return IsAnd ? UnsignedICmp : ZeroICmp;
 
-  // X >= Y && Y == 0  -->  Y == 0    FIXME
+  // X >= Y && Y == 0  -->  Y == 0
   // X >= Y || Y == 0  -->  X >= Y
-  if (UnsignedPred == ICmpInst::ICMP_UGE && EqPred == ICmpInst::ICMP_EQ &&
-      !IsAnd)
-    return UnsignedICmp;
+  if (UnsignedPred == ICmpInst::ICMP_UGE && EqPred == ICmpInst::ICMP_EQ)
+    return IsAnd ? ZeroICmp : UnsignedICmp;
 
   // X > Y && Y == 0  -->  Y == 0  iff X != 0
   // X > Y || Y == 0  -->  X > Y   iff X != 0

Modified: llvm/trunk/test/Transforms/InstSimplify/unsigned-range-checks.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/unsigned-range-checks.ll?rev=372491&r1=372490&r2=372491&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/unsigned-range-checks.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/unsigned-range-checks.ll Sat Sep 21 15:27:39 2019
@@ -84,9 +84,7 @@ define i1 @t7(i8 %x, i8 %y) {
 define i1 @t8(i8 %x, i8 %y) {
 ; CHECK-LABEL: @t8(
 ; CHECK-NEXT:    [[NOT_NULL:%.*]] = icmp eq i8 [[Y:%.*]], 0
-; CHECK-NEXT:    [[NO_UNDERFLOW:%.*]] = icmp ule i8 [[Y]], [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = and i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 [[NOT_NULL]]
 ;
   %not_null = icmp eq i8 %y, 0
   %no_underflow = icmp ule i8 %y, %x