[llvm] [InstCombine][AArch64] Combine ANDs with two constant CMPHS (PR #213995)

[Paul Walker via llvm-commits]

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@@ -3392,6 +3392,46 @@ static std::optional<Instruction *> instCombineSVEUMin(InstCombiner &IC,
   return std::nullopt;
 }
 
+static std::optional<Instruction *> instCombineSVEAnd(InstCombiner &IC,
+                                                      IntrinsicInst &II) {
+  // and(cmphs(pg, C0, A), cmphs(pg, A, C1))
+  // ->
+  // cmphs(pg, C0 - C1, sub(pg, A, C1))
+  constexpr Intrinsic::ID CmphsID = Intrinsic::aarch64_sve_cmphs;
+  Value *Pg = II.getOperand(0);
+  Value *LHS = II.getOperand(1);
+  Value *RHS = II.getOperand(2);
+
+  Value *A, *PgLHS, *PgRHS;
+  uint64_t ConstA, ConstB;
+  if (!match(LHS, m_Intrinsic<CmphsID>(m_Value(PgLHS), m_ConstantInt(ConstA),
+                                       m_Value(A))) ||
+      !match(RHS, m_Intrinsic<CmphsID>(m_Value(PgRHS), m_Specific(A),
+                                       m_ConstantInt(ConstB))) ||
+      !LHS->hasOneUser() || !RHS->hasOneUser())
+    return std::nullopt;
+
+  // Always false regardless of predication
+  if (ConstB > ConstA)
+    return IC.replaceInstUsesWith(II, Constant::getNullValue(II.getType()));
----------------
paulwalker-arm wrote:

Sorry, my mistake.  I was thinking about the compares in isolation and forgot about the and.

https://github.com/llvm/llvm-project/pull/213995