rearrange two transforms, since one subsumes the other. Make the shift-exactness
xform recurse.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131888 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index f3d1061..a9b60d3 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -29,23 +29,8 @@
// code.
if (!V->hasOneUse()) return 0;
-
- // (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())) {
- if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
- I->setIsExact();
- return I;
- }
-
- if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
- I->setHasNoUnsignedWrap();
- return I;
- }
- }
-
+ 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;
@@ -57,12 +42,34 @@
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();
+ MadeChange = true;
+ }
+
+ if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
+ I->setHasNoUnsignedWrap();
+ MadeChange = true;
+ }
+ }
+
// 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;
}