[Mlir-commits] [mlir] 9c442c7 - [mlir][math] Set llvm readnone attribute for libm functions.

[Slava Zakharin]

Author: Slava Zakharin
Date: 2022-08-29T13:03:12-07:00
New Revision: 9c442c7d002184fb1abd32ea7f88481bd21281f2

URL: https://github.com/llvm/llvm-project/commit/9c442c7d002184fb1abd32ea7f88481bd21281f2
DIFF: https://github.com/llvm/llvm-project/commit/9c442c7d002184fb1abd32ea7f88481bd21281f2.diff

LOG: [mlir][math] Set llvm readnone attribute for libm functions.

Math dialect operations currently do not limit transformations
applied to them, which means that they potentially behave like
clang's -ffast-math mathematics. Clang marks math functions with
readnone attribute enabling more optimizations.

This change does the same for functions used by MathToLibm convertor.
In particular, this enables LLVM LICM for tan() call in
Polyhedron/mp_prop_design_11 compiled with flang.

Differential Revision: https://reviews.llvm.org/D131031

Added: 
    

Modified: 
    mlir/lib/Conversion/MathToLibm/MathToLibm.cpp
    mlir/test/Conversion/MathToLibm/convert-to-libm.mlir

Removed: 
    


################################################################################
diff  --git a/mlir/lib/Conversion/MathToLibm/MathToLibm.cpp b/mlir/lib/Conversion/MathToLibm/MathToLibm.cpp
index 5071d60f9e473..6dcf4532dd824 100644
--- a/mlir/lib/Conversion/MathToLibm/MathToLibm.cpp
+++ b/mlir/lib/Conversion/MathToLibm/MathToLibm.cpp
@@ -11,6 +11,7 @@
 #include "../PassDetail.h"
 #include "mlir/Dialect/Arithmetic/IR/Arithmetic.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/Dialect/Math/IR/Math.h"
 #include "mlir/Dialect/Utils/IndexingUtils.h"
 #include "mlir/Dialect/Vector/IR/VectorOps.h"
@@ -129,6 +130,14 @@ ScalarOpToLibmCall<Op>::matchAndRewrite(Op op,
     opFunc = rewriter.create<func::FuncOp>(rewriter.getUnknownLoc(), name,
                                            opFunctionTy);
     opFunc.setPrivate();
+
+    // By definition Math dialect operations imply LLVM's "readnone"
+    // function attribute, so we can set it here to provide more
+    // optimization opportunities (e.g. LICM) for backends targeting LLVM IR.
+    // This will have to be changed, when strict FP behavior is supported
+    // by Math dialect.
+    opFunc->setAttr(LLVM::LLVMDialect::getReadnoneAttrName(),
+                    UnitAttr::get(rewriter.getContext()));
   }
   assert(isa<FunctionOpInterface>(SymbolTable::lookupSymbolIn(module, name)));
 

diff  --git a/mlir/test/Conversion/MathToLibm/convert-to-libm.mlir b/mlir/test/Conversion/MathToLibm/convert-to-libm.mlir
index 641dd568fe494..2f00eaf53d91c 100644
--- a/mlir/test/Conversion/MathToLibm/convert-to-libm.mlir
+++ b/mlir/test/Conversion/MathToLibm/convert-to-libm.mlir
@@ -1,29 +1,29 @@
 // RUN: mlir-opt %s -convert-math-to-libm -canonicalize | FileCheck %s
 
-// CHECK-DAG: @atan(f64) -> f64
-// CHECK-DAG: @atanf(f32) -> f32
-// CHECK-DAG: @erf(f64) -> f64
-// CHECK-DAG: @erff(f32) -> f32
-// CHECK-DAG: @expm1(f64) -> f64
-// CHECK-DAG: @expm1f(f32) -> f32
-// CHECK-DAG: @atan2(f64, f64) -> f64
-// CHECK-DAG: @atan2f(f32, f32) -> f32
-// CHECK-DAG: @tan(f64) -> f64
-// CHECK-DAG: @tanf(f32) -> f32
-// CHECK-DAG: @tanh(f64) -> f64
-// CHECK-DAG: @tanhf(f32) -> f32
-// CHECK-DAG: @round(f64) -> f64
-// CHECK-DAG: @roundf(f32) -> f32
-// CHECK-DAG: @roundeven(f64) -> f64
-// CHECK-DAG: @roundevenf(f32) -> f32
-// CHECK-DAG: @cos(f64) -> f64
-// CHECK-DAG: @cosf(f32) -> f32
-// CHECK-DAG: @sin(f64) -> f64
-// CHECK-DAG: @sinf(f32) -> f32
-// CHECK-DAG: @floor(f64) -> f64
-// CHECK-DAG: @floorf(f32) -> f32
-// CHECK-DAG: @ceil(f64) -> f64
-// CHECK-DAG: @ceilf(f32) -> f32
+// CHECK-DAG: @atan(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @atanf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @erf(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @erff(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @expm1(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @expm1f(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @atan2(f64, f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @atan2f(f32, f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @tan(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @tanf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @tanh(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @tanhf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @round(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @roundf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @roundeven(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @roundevenf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @cos(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @cosf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @sin(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @sinf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @floor(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @floorf(f32) -> f32 attributes {llvm.readnone}
+// CHECK-DAG: @ceil(f64) -> f64 attributes {llvm.readnone}
+// CHECK-DAG: @ceilf(f32) -> f32 attributes {llvm.readnone}
 
 // CHECK-LABEL: func @atan_caller
 // CHECK-SAME: %[[FLOAT:.*]]: f32