[GlobalISel] list undocumented opcodes in docs (#119089)

Author: Thorsten Schütt

llvm/docs/GlobalISel/GenericOpcode.rst

@@ -474,6 +474,9 @@ undefined.
   %2:_(s33) = G_CTLZ_ZERO_UNDEF %1
   %2:_(s33) = G_CTTZ_ZERO_UNDEF %1
 
+G_ABDS, G_ABDU
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 Compute the absolute difference (signed and unsigned), e.g. abs(x-y).
 
 .. code-block:: none
@@ -1131,3 +1134,6 @@ G_CONSTANT_FOLD_BARRIER
 This operation is used as an opaque barrier to prevent constant folding. Combines
 and other transformations should not look through this. These have no other
 semantics and can be safely eliminated if a target chooses.
+
+
+Unlisted: G_STACKSAVE, G_STACKRESTORE, G_FSHL, G_FSHR, G_SMULFIX, G_UMULFIX, G_SMULFIXSAT, G_UMULFIXSAT, G_SDIVFIX, G_UDIVFIX, G_SDIVFIXSAT, G_UDIVFIXSAT, G_FPOWI, G_FEXP10, G_FLDEXP, G_FFREXP, G_GET_FPENV, G_SET_FPENV, G_RESET_FPENV, G_GET_FPMODE, G_SET_FPMODE, G_RESET_FPMODE, G_INTRINSIC_FPTRUNC_ROUND, G_INTRINSIC_LRINT, G_INTRINSIC_LLRINT, G_INTRINSIC_ROUNDEVEN, G_READCYCLECOUNTER, G_READSTEADYCOUNTER, G_PREFETCH, G_READ_REGISTER, G_WRITE_REGISTER, G_STRICT_FADD, G_STRICT_FSUB, G_STRICT_FMUL, G_STRICT_FDIV, G_STRICT_FREM, G_STRICT_FMA, G_STRICT_FSQRT, G_STRICT_FLDEXP, G_ASSERT_ALIGN