[llvm] [DAG] Support saturated truncate (PR #99418)

[David Green via llvm-commits]

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@@ -5418,64 +5418,62 @@ def VImm7FFF: PatLeaf<(AArch64movi_msl (i32 127), (i32 264))>;
 def VImm8000: PatLeaf<(AArch64mvni_msl (i32 127), (i32 264))>;
 
 // trunc(umin(X, 255)) -> UQXTRN v8i8
-def : Pat<(v8i8 (trunc (umin (v8i16 V128:$Vn), (v8i16 VImmFF)))),
+def : Pat<(v8i8 (truncusat_u (v8i16 V128:$Vn))),
           (UQXTNv8i8 V128:$Vn)>;
 // trunc(umin(X, 65535)) -> UQXTRN v4i16
-def : Pat<(v4i16 (trunc (umin (v4i32 V128:$Vn), (v4i32 VImmFFFF)))),
+def : Pat<(v4i16 (truncusat_u (v4i32 V128:$Vn))),
           (UQXTNv4i16 V128:$Vn)>;
+// trunc(umin(X, 4294967295)) -> UQXTRN v2i32
+def : Pat<(v2i32 (truncusat_u (v2i64 V128:$Vn))),
+          (UQXTNv2i32 V128:$Vn)>;
 // trunc(smin(smax(X, -128), 128)) -> SQXTRN
-//  with reversed min/max
-def : Pat<(v8i8 (trunc (smin (smax (v8i16 V128:$Vn), (v8i16 VImm80)),
-                             (v8i16 VImm7F)))),
-          (SQXTNv8i8 V128:$Vn)>;
-def : Pat<(v8i8 (trunc (smax (smin (v8i16 V128:$Vn), (v8i16 VImm7F)),
-                             (v8i16 VImm80)))),
+def : Pat<(v8i8 (truncssat_s (v8i16 V128:$Vn))),
           (SQXTNv8i8 V128:$Vn)>;
+// trunc(umin(smax(X, 0), 255)) -> SQXTUN
+def : Pat<(v8i8 (truncssat_u (v8i16 V128:$Vn))),
+          (SQXTUNv8i8 V128:$Vn)>;
 // trunc(smin(smax(X, -32768), 32767)) -> SQXTRN
-//  with reversed min/max
-def : Pat<(v4i16 (trunc (smin (smax (v4i32 V128:$Vn), (v4i32 VImm8000)),
-                              (v4i32 VImm7FFF)))),
+def : Pat<(v4i16 (truncssat_s (v4i32 V128:$Vn))),
           (SQXTNv4i16 V128:$Vn)>;
-def : Pat<(v4i16 (trunc (smax (smin (v4i32 V128:$Vn), (v4i32 VImm7FFF)),
-                              (v4i32 VImm8000)))),
+// trunc(smin(smax(X, -2147483648), 2147483647)) -> SQXTRN
+def : Pat<(v2i32 (truncssat_s (v2i64 V128:$Vn))),
           (SQXTNv4i16 V128:$Vn)>;
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davemgreen wrote:

SQXTNv4i16 -> SQXTNv2i32

Can you add a SQXTUNv2i32 version too?

https://github.com/llvm/llvm-project/pull/99418