[PatternMatch] Make m_c_ICmp swap the predicate (PR42801)

This addresses https://bugs.llvm.org/show_bug.cgi?id=42801.
The m_c_ICmp() matcher is changed to provide the swapped predicate
if the operands are swapped.

Existing uses of m_c_ICmp() fall in one of two categories: Working
on equality predicates only, where swapping is irrelevant.
Or performing a manual swap, in which case this patch removes it.

The only exception is the foldICmpWithLowBitMaskedVal() fold, which
does not swap the predicate, and instead reasons about whether
a swap occurred or not for each predicate. Getting the swapped
predicate allows us to merge the logic for pairs of predicates,
instead of duplicating it.

Differential Revision: https://reviews.llvm.org/D72976

1 files changed, 0 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index ad6765e..7b9de94 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -592,10 +592,6 @@ static bool isKnownNonZeroFromAssume(const Value *V, const Query &Q) {
     CmpInst::Predicate Pred;
     if (!match(Cmp, m_c_ICmp(Pred, m_V, m_Value(RHS))))
       return false;
-    // Canonicalize 'v' to be on the LHS of the comparison.
-    if (Cmp->getOperand(1) != RHS)
-      Pred = CmpInst::getSwappedPredicate(Pred);
-
     // assume(v u> y) -> assume(v != 0)
     if (Pred == ICmpInst::ICMP_UGT)
       return true;