[llvm] [X86][GISel] Add DU chain lookups for LOAD & STORE (PR #87453)

[Evgenii Kudriashov via llvm-commits]

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@@ -68,6 +71,143 @@ X86RegisterBankInfo::getRegBankFromRegClass(const TargetRegisterClass &RC,
   llvm_unreachable("Unsupported register kind yet.");
 }
 
+// Returns whether opcode \p Opc is a pre-isel generic floating-point opcode,
+// having only floating-point operands.
+static bool isPreISelGenericFloatingPointOpcode(unsigned Opc) {
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e-kud wrote:

Does it make sense to have a field in instruction definitions similarly to `hasSideEffects` instead of having such switches? Or do we consider DU approach as a temporary measure until proper float types are implemented, so this switch will be no longer needed.

https://github.com/llvm/llvm-project/pull/87453