[llvm-commits] [llvm] r169942 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp test/Transforms/InstCombine/shift.ll

[Shuxin Yang]

Author: shuxin_yang
Date: Tue Dec 11 18:29:03 2012
New Revision: 169942

URL: http://llvm.org/viewvc/llvm-project?rev=169942&view=rev
Log:
- Fix a problematic way in creating all-the-1 APInt.
- Propagate "exact" bit of [l|a]shr instruction.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
    llvm/trunk/test/Transforms/InstCombine/shift.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp?rev=169942&r1=169941&r2=169942&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp Tue Dec 11 18:29:03 2012
@@ -858,8 +858,8 @@
   Value *VarX = Shr->getOperand(0);
   Type *Ty = VarX->getType();
 
-  APInt BitMask1(Ty->getIntegerBitWidth(), (uint64_t)-1);
-  APInt BitMask2(Ty->getIntegerBitWidth(), (uint64_t)-1);
+  APInt BitMask1(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
+  APInt BitMask2(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
 
   bool isLshr = (Shr->getOpcode() == Instruction::LShr);
   BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :
@@ -891,6 +891,8 @@
       Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
       New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) :
                      BinaryOperator::CreateAShr(VarX, Amt);
+      if (cast<BinaryOperator>(Shr)->isExact())
+        New->setIsExact(true);
     }
 
     return InsertNewInstWith(New, *Shl);

Modified: llvm/trunk/test/Transforms/InstCombine/shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/shift.ll?rev=169942&r1=169941&r2=169942&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/shift.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/shift.ll Tue Dec 11 18:29:03 2012
@@ -735,3 +735,13 @@
 ; CHECK: @test61
 ; CHECK: ashr i32 %x, 4
 }
+
+; propagate "exact" trait
+define i32 @test62(i32 %x) {
+  %shr = ashr exact i32 %x, 4
+  %shl = shl i32 %shr, 1
+  %or = or i32 %shl, 1
+  ret i32 %or
+; CHECK: @test62
+; CHECK: ashr exact i32 %x, 3
+}