[flang] optimize acosd precision (#154118)

Part of #150452.

Author: c8ef

flang/lib/Optimizer/Builder/IntrinsicCall.cpp

@@ -2672,10 +2672,11 @@ mlir::Value IntrinsicLibrary::genAcosd(mlir::Type resultType,
       mlir::FunctionType::get(context, {resultType}, {args[0].getType()});
   mlir::Value result =
       getRuntimeCallGenerator("acos", ftype)(builder, loc, {args[0]});
-  llvm::APFloat pi = llvm::APFloat(llvm::numbers::pi);
-  mlir::Value dfactor = builder.createRealConstant(
-      loc, mlir::Float64Type::get(context), llvm::APFloat(180.0) / pi);
-  mlir::Value factor = builder.createConvert(loc, args[0].getType(), dfactor);
+  const llvm::fltSemantics &fltSem =
+      llvm::cast<mlir::FloatType>(resultType).getFloatSemantics();
+  llvm::APFloat pi = llvm::APFloat(fltSem, llvm::numbers::pis);
+  mlir::Value factor = builder.createRealConstant(
+      loc, resultType, llvm::APFloat(fltSem, "180.0") / pi);
   return mlir::arith::MulFOp::create(builder, loc, result, factor);
 }
 

flang/test/Lower/Intrinsics/acosd.f90

@@ -1,3 +1,4 @@
+! REQUIRES: flang-supports-f128-math
 ! RUN: %flang_fc1 -emit-fir %s -o - | FileCheck %s --check-prefixes="CHECK"
 
 function test_real4(x)
@@ -6,9 +7,8 @@ function test_real4(x)
 end function
 
 ! CHECK-LABEL: @_QPtest_real4
-! CHECK: %[[dfactor:.*]] = arith.constant 57.295779513082323 : f64
+! CHECK: %[[factor:.*]] = arith.constant 57.2957763 : f32
 ! CHECK: %[[result:.*]] = math.acos %{{.*}} fastmath<contract> : f32
-! CHECK: %[[factor:.*]] = fir.convert %[[dfactor]] : (f64) -> f32
 ! CHECK: %[[arg:.*]] = arith.mulf %[[result]], %[[factor]] fastmath<contract> : f32
 
 function test_real8(x)
@@ -17,6 +17,16 @@ function test_real8(x)
 end function
 
 ! CHECK-LABEL: @_QPtest_real8
-! CHECK: %[[dfactor:.*]] = arith.constant 57.295779513082323 : f64
+! CHECK: %[[factor:.*]] = arith.constant 57.295779513082323 : f64
 ! CHECK: %[[result:.*]] = math.acos %{{.*}} fastmath<contract> : f64
-! CHECK: %[[arg:.*]] = arith.mulf %[[result]], %[[dfactor]] fastmath<contract> : f64
+! CHECK: %[[arg:.*]] = arith.mulf %[[result]], %[[factor]] fastmath<contract> : f64
+
+function test_real16(x)
+  real(16) :: x, test_real16
+  test_real16 = acosd(x)
+end function
+
+! CHECK-LABEL: @_QPtest_real16
+! CHECK: %[[factor:.*]] = arith.constant 57.295779513082320876798154814105{{.*}} : f128
+! CHECK: %[[result:.*]] = fir.call @_FortranAAcosF128({{.*}}) fastmath<contract> : (f128) -> f128
+! CHECK: %[[arg:.*]] = arith.mulf %[[result]], %[[factor]] fastmath<contract> : f128