[clang] [CIR] Add cir-simplify pass (PR #138317)

[Andy Kaylor via cfe-commits]

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@@ -0,0 +1,60 @@
+// RUN: cir-opt -cir-canonicalize -cir-simplify -o %t.cir %s
+// RUN: FileCheck --input-file=%t.cir %s
+
+!s32i = !cir.int<s, 32>
+
+module {
+  cir.func @fold_ternary(%arg0: !s32i, %arg1: !s32i) -> !s32i {
+    %0 = cir.const #cir.bool<false> : !cir.bool
+    %1 = cir.ternary (%0, true {
+      cir.yield %arg0 : !s32i
+    }, false {
+      cir.yield %arg1 : !s32i
+    }) : (!cir.bool) -> !s32i
+    cir.return %1 : !s32i
+  }
+
+  //      CHECK: cir.func @fold_ternary(%{{.+}}: !s32i, %[[ARG:.+]]: !s32i) -> !s32i {
+  // CHECK-NEXT:   cir.return %[[ARG]] : !s32i
+  // CHECK-NEXT: }
+
+  cir.func @simplify_ternary(%arg0 : !cir.bool, %arg1 : !s32i) -> !s32i {
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andykaylor wrote:

Can you add a case where the constant is returned in the false branch?

https://github.com/llvm/llvm-project/pull/138317