[llvm-commits] [llvm] r53271 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/2008-07-08-SubAnd.ll
Nick Lewycky
nicholas at mxc.ca
Tue Jul 8 21:32:37 PDT 2008
Author: nicholas
Date: Tue Jul 8 23:32:37 2008
New Revision: 53271
URL: http://llvm.org/viewvc/llvm-project?rev=53271&view=rev
Log:
Reduce x - y to -y when we know the 'x' part will get masked off anyways.
Added:
llvm/trunk/test/Transforms/InstCombine/2008-07-08-SubAnd.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=53271&r1=53270&r2=53271&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Tue Jul 8 23:32:37 2008
@@ -3461,6 +3461,17 @@
// ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
return BinaryOperator::CreateAnd(V, AndRHS);
+
+ // (A - N) & AndRHS -> -N & AndRHS where A & AndRHS == 0
+ if (Op0I->hasOneUse() && MaskedValueIsZero(Op0LHS, AndRHSMask)) {
+ ConstantInt *A = dyn_cast<ConstantInt>(Op0LHS);
+ if (!A || !A->isZero()) {
+ Instruction *NewNeg = BinaryOperator::CreateNeg(Op0RHS);
+ InsertNewInstBefore(NewNeg, I);
+ return BinaryOperator::CreateAnd(NewNeg, AndRHS);
+ }
+ }
+
break;
}
@@ -3780,7 +3791,7 @@
}
}
}
-
+
return Changed ? &I : 0;
}
Added: llvm/trunk/test/Transforms/InstCombine/2008-07-08-SubAnd.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2008-07-08-SubAnd.ll?rev=53271&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/2008-07-08-SubAnd.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/2008-07-08-SubAnd.ll Tue Jul 8 23:32:37 2008
@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep -v {i32 8}
+; PR2330
+
+define i32 @a(i32 %a) nounwind {
+entry:
+ %tmp2 = sub i32 8, %a ; <i32> [#uses=1]
+ %tmp3 = and i32 %tmp2, 7 ; <i32> [#uses=1]
+ ret i32 %tmp3
+}
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