[mlir][spirv] Remove invalid canon pattern for GL.Length (llvm#164301)

This rewrite does not preserve numerics: for example, we'd expect the
maximum fp value to yield Inf instead of identity.

`GL.Length` does not allow for fast math flags, so we need to remove
this. Special cases (constants) can be handled via a folder if someone
wants to implement one.

Author: kuhar

mlir/lib/Dialect/SPIRV/IR/SPIRVCanonicalization.td

@@ -75,11 +75,3 @@ def ConvertComparisonIntoClamp2_#CmpClampPair[0] : Pat<
         )),
     (CmpClampPair[1] $input, $min, $max)>;
 }
-
-//===----------------------------------------------------------------------===//
-// spirv.GL.Length -> spirv.GL.FAbs
-//===----------------------------------------------------------------------===//
-
-def ConvertGLLengthToGLFAbs : Pat<
-    (SPIRV_GLLengthOp SPIRV_Float:$operand),
-    (SPIRV_GLFAbsOp $operand)>;

mlir/lib/Dialect/SPIRV/IR/SPIRVGLCanonicalization.cpp

@@ -34,8 +34,8 @@ void populateSPIRVGLCanonicalizationPatterns(RewritePatternSet &results) {
               ConvertComparisonIntoClamp2_SPIRV_SLessThanOp,
               ConvertComparisonIntoClamp2_SPIRV_SLessThanEqualOp,
               ConvertComparisonIntoClamp2_SPIRV_ULessThanOp,
-              ConvertComparisonIntoClamp2_SPIRV_ULessThanEqualOp,
-              ConvertGLLengthToGLFAbs>(results.getContext());
+              ConvertComparisonIntoClamp2_SPIRV_ULessThanEqualOp>(
+      results.getContext());
 }
 } // namespace spirv
 } // namespace mlir

mlir/test/Dialect/SPIRV/Transforms/gl-canonicalize.mlir

@@ -177,25 +177,3 @@ func.func @clamp_ulessthanequal(%input: i32, %min: i32, %max: i32) -> i32 {
   // CHECK-NEXT: spirv.ReturnValue [[RES]]
   spirv.ReturnValue %2 : i32
 }
-
-// -----
-
-//===----------------------------------------------------------------------===//
-// spirv.GL.Length
-//===----------------------------------------------------------------------===//
-
-// CHECK-LABEL: @convert_length_into_fabs_scalar
-func.func @convert_length_into_fabs_scalar(%arg0 : f32) -> f32 {
-  //CHECK: spirv.GL.FAbs {{%.*}} : f32
-  //CHECK-NOT: spirv.GL.Length
-  %0 = spirv.GL.Length %arg0 : f32 -> f32
-  spirv.ReturnValue %0 : f32
-}
-
-// CHECK-LABEL: @dont_convert_length_into_fabs_vec
-func.func @dont_convert_length_into_fabs_vec(%arg0 : vector<3xf32>) -> f32 {
-  //CHECK: spirv.GL.Length {{%.*}} : vector<3xf32> -> f32
-  //CHECK-NOT: spirv.GL.FAbs
-  %0 = spirv.GL.Length %arg0 : vector<3xf32> -> f32
-  spirv.ReturnValue %0 : f32
-}