[llvm] [SandboxIR] Implement CmpInst, FCmpInst, and ICmpInst (PR #106301)

[via llvm-commits]

================
@@ -4392,6 +4392,159 @@ define void @foo(i32 %arg) {
   EXPECT_EQ(NewPHI->getNumIncomingValues(), PHI->getNumIncomingValues());
 }
 
+static void checkSwapOperands(sandboxir::Context &Ctx,
+                              llvm::sandboxir::CmpInst *Cmp,
+                              llvm::CmpInst *LLVMCmp) {
+  auto OrigOp0 = Cmp->getOperand(0);
+  auto OrigOp1 = Cmp->getOperand(1);
+  EXPECT_EQ(Ctx.getValue(LLVMCmp->getOperand(0)), OrigOp0);
+  EXPECT_EQ(Ctx.getValue(LLVMCmp->getOperand(1)), OrigOp1);
+  // This checks the dispatch mechanism in CmpInst, as well as
+  // the specific implementations.
+  Cmp->swapOperands();
+  EXPECT_EQ(Ctx.getValue(LLVMCmp->getOperand(1)), OrigOp0);
+  EXPECT_EQ(Ctx.getValue(LLVMCmp->getOperand(0)), OrigOp1);
----------------
vporpo wrote:

We have already checked the predicates in CmpInst's tests, but I guess there is no harm in checking them here too?
```
auto OrigPred = LLVMCmp->getPredicate();
auto NewPred = sandboxir::CmpInst::getInversePredicate(OrigPred);
Cmp->swapOperands();
EXPECT_NE(NewPred, OrigPred);
EXPECT_EQ(Cmp->getPredicate(), NewPred)`
```

https://github.com/llvm/llvm-project/pull/106301