[PATCH] D14223: Do (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1 rather than (A == C1 || A == C2) -> (A | (C1 ^ C2)) == C2 when C1 ^ C2 is a power of 2.

[Amaury SECHET via llvm-commits]

deadalnix created this revision.
deadalnix added reviewers: chandlerc, kuba, majnemer, craig.topper.
deadalnix added a subscriber: llvm-commits.

As per title.

http://reviews.llvm.org/D14223

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/icmp.ll
  test/Transforms/InstCombine/load-cmp.ll
  test/Transforms/InstCombine/or.ll

Index: test/Transforms/InstCombine/or.ll
===================================================================
--- test/Transforms/InstCombine/or.ll
+++ test/Transforms/InstCombine/or.ll
@@ -182,7 +182,7 @@
         %D = or i1 %B, %C
         ret i1 %D
 ; CHECK-LABEL: @test19(
-; CHECK: and i32
+; CHECK: or i32
 ; CHECK: icmp eq 
 ; CHECK: ret i1
 }
Index: test/Transforms/InstCombine/load-cmp.ll
===================================================================
--- test/Transforms/InstCombine/load-cmp.ll
+++ test/Transforms/InstCombine/load-cmp.ll
@@ -148,8 +148,8 @@
   %S = icmp eq i16 %R, 0
   ret i1 %S
 ; CHECK-LABEL: @test8(
-; CHECK-NEXT: and i32 %X, -2
-; CHECK-NEXT: icmp eq i32 {{.*}}, 8
+; CHECK-NEXT: or i32 %X, 1
+; CHECK-NEXT: icmp eq i32 {{.*}}, 9
 ; CHECK-NEXT: ret i1
 }
 
Index: test/Transforms/InstCombine/icmp.ll
===================================================================
--- test/Transforms/InstCombine/icmp.ll
+++ test/Transforms/InstCombine/icmp.ll
@@ -819,8 +819,8 @@
 
 ; PR14708
 ; CHECK-LABEL: @test69(
-; CHECK: %1 = and i32 %c, -33
-; CHECK: %2 = icmp eq i32 %1, 65
+; CHECK: %1 = or i32 %c, 32
+; CHECK: %2 = icmp eq i32 %1, 97
 ; CHECK: ret i1 %2
 define i1 @test69(i32 %c) nounwind uwtable {
   %1 = icmp eq i32 %c, 97
Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1962,14 +1962,14 @@
     case ICmpInst::ICMP_EQ:
       if (LHS->getOperand(0) == RHS->getOperand(0)) {
         // if LHSCst and RHSCst differ only by one bit:
-        // (A == C1 || A == C2) -> (A & ~(C1 ^ C2)) == C1
+        // (A == C1 || A == C2) -> (A | (C1 ^ C2)) == C2
         assert(LHSCst->getValue().ule(LHSCst->getValue()));
 
         APInt Xor = LHSCst->getValue() ^ RHSCst->getValue();
         if (Xor.isPowerOf2()) {
-          Value *NegCst = Builder->getInt(~Xor);
-          Value *And = Builder->CreateAnd(LHS->getOperand(0), NegCst);
-          return Builder->CreateICmp(ICmpInst::ICMP_EQ, And, LHSCst);
+          Value *Cst = Builder->getInt(Xor);
+          Value *Or = Builder->CreateOr(LHS->getOperand(0), Cst);
+          return Builder->CreateICmp(ICmpInst::ICMP_EQ, Or, RHSCst);
         }
       }
 


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