optimize:
void a(int x) { if (((1<<x)&8)==0) b(); }
into "x != 3", which occurs over 100 times in 403.gcc but in no
other program in llvm-test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119922 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index d7e2b72..8a35a5f 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1744,14 +1744,84 @@
// simplify this comparison. For example, (x&4) < 8 is always true.
switch (I.getPredicate()) {
default: llvm_unreachable("Unknown icmp opcode!");
- case ICmpInst::ICMP_EQ:
+ case ICmpInst::ICMP_EQ: {
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
+
+ // If all bits are known zero except for one, then we know at most one
+ // bit is set. If the comparison is against zero, then this is a check
+ // to see if *that* bit is set.
+ APInt Op0KnownZeroInverted = ~Op0KnownZero;
+ if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ // If the LHS is an AND with the same constant, look through it.
+ Value *LHS = 0;
+ ConstantInt *LHSC = 0;
+ if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
+ LHSC->getValue() != Op0KnownZeroInverted)
+ LHS = Op0;
+
+ // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
+ // then turn "((1 << x)&8) == 0" into "x == 3".
+ Value *X = 0;
+ if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
+ unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
+
+ // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
+ // then turn "((8 >>u x)&1) == 0" into "x == 3".
+ ConstantInt *CI = 0;
+ if (Op0KnownZeroInverted == 1 &&
+ match(LHS, m_LShr(m_ConstantInt(CI), m_Value(X))) &&
+ CI->getValue().isPowerOf2()) {
+ unsigned CmpVal = CI->getValue().countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_EQ, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
+ }
+
break;
- case ICmpInst::ICMP_NE:
+ }
+ case ICmpInst::ICMP_NE: {
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
+
+ // If all bits are known zero except for one, then we know at most one
+ // bit is set. If the comparison is against zero, then this is a check
+ // to see if *that* bit is set.
+ APInt Op0KnownZeroInverted = ~Op0KnownZero;
+ if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
+ // If the LHS is an AND with the same constant, look through it.
+ Value *LHS = 0;
+ ConstantInt *LHSC = 0;
+ if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
+ LHSC->getValue() != Op0KnownZeroInverted)
+ LHS = Op0;
+
+ // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
+ // then turn "((1 << x)&8) != 0" into "x != 3".
+ Value *X = 0;
+ if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
+ unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
+
+ // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
+ // then turn "((8 >>u x)&1) != 0" into "x != 3".
+ ConstantInt *CI = 0;
+ if (Op0KnownZeroInverted == 1 &&
+ match(LHS, m_LShr(m_ConstantInt(CI), m_Value(X))) &&
+ CI->getValue().isPowerOf2()) {
+ unsigned CmpVal = CI->getValue().countTrailingZeros();
+ return new ICmpInst(ICmpInst::ICMP_NE, X,
+ ConstantInt::get(X->getType(), CmpVal));
+ }
+ }
+
break;
+ }
case ICmpInst::ICMP_ULT:
if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));