[compiler-rt] Compile __powitf2 under wasm

[sbc100]

Summary

See https://github.com/emscripten-core/emscripten/issues/10374
See https://reviews.llvm.org/D74274

[sbc100]

rebase

[sbc100]

Any idea why this file was listed under x86_ARCH_SOURCES? But only seems to active for ARCH_PPC?

[sbc100]

I think the reason we noticed this being missing under wasm is because we (somewhat unusually) use fp128 for long double

[phosek]

In D74275#1865769, @sbc100 wrote:

Any idea why this file was listed under x86_ARCH_SOURCES? But only seems to active for ARCH_PPC?

That looks like a bug to me.

[efriedma]

compiler-rt/lib/builtins/CMakeLists.txt

147 ↗

(On Diff #243345)

powixf2.c is, in fact, x86-specific. At first glance it might not look like that, but the "x" in the name powixf2 refers exclusively to x86 long double.

compiler-rt/lib/builtins/powitf2.c

16

Please change this so it matches the other 128 long double routines: it should include fp_lib.h, it should use the condition #if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT), and it should use fp_t instead of explicitly writing out "long double".

[sbc100]

• revert cmake
• feedback

[sbc100]

compiler-rt/lib/builtins/CMakeLists.txt

147 ↗

(On Diff #243345)

Indeed, sorry I misread/misunderstood.

compiler-rt/lib/builtins/powitf2.c

16

Great those macros looks like what I'm looking for.

Would you mind doing the fp_t change as a followup? I don't know this codebase well enough to feel confident doing that part.

[efriedma]

LGTM

compiler-rt/lib/builtins/powitf2.c

 //===-- powitf2.cpp - Implement __powitf2 ---------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements __powitf2 for the compiler_rt library.
 //
 //===----------------------------------------------------------------------===//
 
-#include "int_lib.h"
+#define QUAD_PRECISION
+#include "fp_lib.h"
 
-#if _ARCH_PPC
+#if defined(CRT_HAS_128BIT) && defined(CRT_LDBL_128BIT)
 
 // Returns: a ^ b
 
 COMPILER_RT_ABI long double __powitf2(long double a, si_int b) {
   const int recip = b < 0;
   long double r = 1;
   while (1) {
     if (b & 1)

compiler-rt/test/builtins/Unit/powitf2_test.c

 // RUN: %clang_builtins %s %librt -o %t && %run %t
 // REQUIRES: librt_has_powitf2
 //===-- powitf2_test.cpp - Test __powitf2 ---------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file tests __powitf2 for the compiler_rt library.
 //
 //===----------------------------------------------------------------------===//
 
 #include <stdio.h>
 
-#if _ARCH_PPC
+#if __LDBL_MANT_DIG__ == 113
 
 #include "int_lib.h"
 #include <math.h>
 
 // Returns: a ^ b
 
 COMPILER_RT_ABI long double __powitf2(long double a, si_int b);
 
 int test__powitf2(long double a, si_int b, long double expected)
 {
     long double x = __powitf2(a, b);
     int correct = (x == expected) && (signbit(x) == signbit(expected));
     if (!correct)
         printf("error in __powitf2(%Lf, %d) = %Lf, expected %Lf\n",
                a, b, x, expected);
     return !correct;
 }
 
 #endif
 
 int main()
 {
-#if _ARCH_PPC
+#if __LDBL_MANT_DIG__ == 113
     if (test__powitf2(0, 0, 1))
         return 1;
     if (test__powitf2(1, 0, 1))
         return 1;
     if (test__powitf2(1.5, 0, 1))
         return 1;
     if (test__powitf2(2, 0, 1))
         return 1;
     if (test__powitf2(INFINITY, 0, 1))