[clang] [llvm] [NVPTX] Add conversion intrinsics from/to fp8 types (e4m3, e5m2) (PR #102969)

[Sergey Kozub via cfe-commits]

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@@ -722,6 +722,37 @@ let hasSideEffects = false in {
 
   defm CVT_f16x2 : CVT_FROM_FLOAT_V2_SM80<"f16x2", Int32Regs>;
   defm CVT_bf16x2 : CVT_FROM_FLOAT_V2_SM80<"bf16x2", Int32Regs>;
+
+  // FP8 conversions.
+  multiclass CVT_TO_F8X2<string F8Name> {
+    def _f32 :
+      NVPTXInst<(outs Int16Regs:$dst),
+                (ins Float32Regs:$src1, Float32Regs:$src2, CvtMode:$mode),
+                !strconcat("cvt${mode:base}.satfinite${mode:relu}.",
+                F8Name, "x2.f32 \t$dst, $src1, $src2;"), []>,
+      Requires<[hasPTX<81>, hasSM<89>]>;
+    def _f16x2 :
+      NVPTXInst<(outs Int16Regs:$dst),
+                (ins Int32Regs:$src, CvtMode:$mode),
+                !strconcat("cvt${mode:base}.satfinite${mode:relu}.",
+                F8Name, "x2.f16x2 \t$dst, $src;"), []>,
+      Requires<[hasPTX<81>, hasSM<89>]>;
+  }
+
+  defm CVT_e4m3x2 : CVT_TO_F8X2<"e4m3">;
+  defm CVT_e5m2x2 : CVT_TO_F8X2<"e5m2">;
+
+  multiclass CVT_FROM_F8X2<string F8Name> {
+    def x2 :
+      NVPTXInst<(outs Int32Regs:$dst),
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sergey-kozub wrote:

This one is confusing, "x2" is only there only because (for some reason) I cannot specify an empty suffix.
All the classes in this file use the `CVT_<to>_<from>` pattern. I need to define two classes: CVT_f16x2_e4m3x2 and CVT_f16x2_e5m2.

You're suggesting to rename to `_f16x2` but I guess "multiclass" only supports appending the suffixes, whereas I need "f16x2" to appear in the middle of the class name (in order to conform to the common naming pattern).

Also, "outs" is Int32Regs, and I cannot specify <2xf16> here. This is in line with the other class definitions in this file.


https://github.com/llvm/llvm-project/pull/102969