[llvm-commits] [llvm] r131888 - /llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
Chris Lattner
sabre at nondot.org
Sun May 22 17:32:19 PDT 2011
Author: lattner
Date: Sun May 22 19:32:19 2011
New Revision: 131888
URL: http://llvm.org/viewvc/llvm-project?rev=131888&view=rev
Log:
rearrange two transforms, since one subsumes the other. Make the shift-exactness
xform recurse.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=131888&r1=131887&r2=131888&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Sun May 22 19:32:19 2011
@@ -29,40 +29,47 @@
// code.
if (!V->hasOneUse()) return 0;
+ bool MadeChange = false;
+
+ // ((1 << A) >>u B) --> (1 << (A-B))
+ // Because V cannot be zero, we know that B is less than A.
+ Value *A = 0, *B = 0, *PowerOf2 = 0;
+ if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))),
+ m_Value(B))) &&
+ // The "1" can be any value known to be a power of 2.
+ isPowerOfTwo(PowerOf2, IC.getTargetData())) {
+ A = IC.Builder->CreateSub(A, B, "tmp");
+ return IC.Builder->CreateShl(PowerOf2, A);
+ }
// (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
// inexact. Similarly for <<.
if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
if (I->isLogicalShift() &&
isPowerOfTwo(I->getOperand(0), IC.getTargetData())) {
+ // We know that this is an exact/nuw shift and that the input is a
+ // non-zero context as well.
+ if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC)) {
+ I->setOperand(0, V2);
+ MadeChange = true;
+ }
+
if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
I->setIsExact();
- return I;
+ MadeChange = true;
}
if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
I->setHasNoUnsignedWrap();
- return I;
+ MadeChange = true;
}
}
-
- // ((1 << A) >>u B) --> (1 << (A-B))
- // Because V cannot be zero, we know that B is less than A.
- Value *A = 0, *B = 0, *PowerOf2 = 0;
- if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))),
- m_Value(B))) &&
- // The "1" can be any value known to be a power of 2.
- isPowerOfTwo(PowerOf2, IC.getTargetData())) {
- A = IC.Builder->CreateSub(A, B, "tmp");
- return IC.Builder->CreateShl(PowerOf2, A);
- }
-
+
// TODO: Lots more we could do here:
- // "1 >> X" could get an "isexact" bit.
// If V is a phi node, we can call this on each of its operands.
// "select cond, X, 0" can simplify to "X".
- return 0;
+ return MadeChange ? V : 0;
}
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