Implement review feedback, including additional transforms
(icmp slt (sub A B) 1) -> (icmp sle A B)
icmp sgt (sub A B) -1) -> (icmp sge A B)
and add testcase.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45256 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index d9b4173..e80f0ef 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4785,23 +4785,6 @@
if (isa<UndefValue>(Op1)) // X icmp undef -> undef
return ReplaceInstUsesWith(I, UndefValue::get(Type::Int1Ty));
-
- // (icmp cond (sub m A) 0) ->
- // (icmp cond m A)
- {
- ConstantInt *C1, *C2;
- Value *A;
- // Check both arguments of the compare for a matching subtract.
- if (match(Op0, m_ConstantInt(C1)) && C1->getValue() == 0 &&
- match(Op1, m_Sub(m_ConstantInt(C2), m_Value(A)))) {
- // We managed to fold the add into the RHS of the select condition.
- return new ICmpInst(I.getPredicate(), A, C2);
- } else if (match(Op1, m_ConstantInt(C1)) && C1->getValue() == 0 &&
- match(Op0, m_Sub(m_ConstantInt(C2), m_Value(A)))) {
- // We managed to fold the add into the LHS of the select condition.
- return new ICmpInst(I.getPredicate(), C2, A);
- }
- }
// icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
// addresses never equal each other! We already know that Op0 != Op1.
@@ -4850,6 +4833,12 @@
// See if we are doing a comparison between a constant and an instruction that
// can be folded into the comparison.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
+ Value *A, *B;
+
+ // (icmp cond (sub A B) 0) -> (icmp cond A B)
+ if (CI->isNullValue() && match(Op0, m_Sub(m_Value(A), m_Value(B))))
+ return new ICmpInst(I.getPredicate(), A, B);
+
switch (I.getPredicate()) {
default: break;
case ICmpInst::ICMP_ULT: // A <u MIN -> FALSE
@@ -4873,6 +4862,10 @@
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMinValuePlusOne(CI,true)) // A <s MIN+1 -> A == MIN
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
+
+ // (icmp slt (sub A B) 1) -> (icmp sle A B)
+ if (CI->isOne() && match(Op0, m_Sub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SLE, A, B);
break;
case ICmpInst::ICMP_UGT:
@@ -4896,6 +4889,11 @@
return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
if (isMaxValueMinusOne(CI, true)) // A >s MAX-1 -> A == MAX
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
+
+ // (icmp sgt (sub A B) -1) -> (icmp sge A B)
+ if (CI->getValue().getSExtValue() == -1 &&
+ match(Op0, m_Sub(m_Value(A), m_Value(B))))
+ return new ICmpInst(ICmpInst::ICMP_SGE, A, B);
break;
case ICmpInst::ICMP_ULE: