[llvm] [GlobalISel] Remove `fp_to_[s/u]int_sat_gi` node (PR #202908)

[Igor Wodiany via llvm-commits]

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@@ -954,6 +954,25 @@ Expected<InstructionMatcher &> GlobalISelEmitter::createAndImportSelDAGMatcher(
       }
     }
 
+    // The SDAG fp_to_[su]int_sat nodes carry a trailing ValueType operand
+    // encoding the saturation width. G_FPTOSI_SAT/G_FPTOUI_SAT instead saturate
+    // to their result type and have no such operand, so drop the trailing child
+    // before matching the operands.
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IgWod wrote:

So just to confirm, we want to add saturation width/type to `G_FPTOSI_SAT/G_FPTOUI_SAT`. Would it make sense to add it as `untyped_imm_0:$sat_width`? This would be similar to `G_SEXT_INREG`.

https://github.com/llvm/llvm-project/pull/202908