[libc] Disable 'DecodeInOtherBases` test on GPU targets

[jhuber6]

Summary

This test is excessively slow on GPU targets, taking anywhere beween 5
and 60 seconds to complete each time it's run. See
https://lab.llvm.org/buildbot/#/builders/55/builds/52203/steps/12/logs/stdio
for an example on the NVPTX buildbot. Simply disable testing this on the
GPU for now.

[jhuber6]

Fix

[michaelrj]

Try disabling just the third set of loops, since the size of the checks grows exponentially it's likely that they're taking up most of the time.

[jhuber6]

Changing to limit the nested loop depth

[michaelrj]

I'd rather not limit the digits to just 0 and 1. If you want to shorten the tests maybe try 16? Otherwise probably just disable the whole test. Having the test enabled and running but not actually checking anything seems like a recipe for confusion.

[jhuber6]

In D155979#4523279, @michaelrj wrote:

I'd rather not limit the digits to just 0 and 1. If you want to shorten the tests maybe try 16? Otherwise probably just disable the whole test. Having the test enabled and running but not actually checking anything seems like a recipe for confusion.

Well we at least get the first loop's checks. This version takes 5ms on my machine, the original takes 6000ms, changing it to 16 takes 500ms.

[michaelrj]

How long does it take with a limit of 36 but disabling the loop that goes to the third digit?

[jhuber6]

In D155979#4523294, @michaelrj wrote:

How long does it take with a limit of 36 but disabling the loop that goes to the third digit?

100ms

[michaelrj]

I think that's the option I would prefer then. That way we get to test all of the 1 and 2 digit cases

[jhuber6]

Disable only tertiary loop

[michaelrj]

libc/test/src/stdlib/StrtolTest.h

202

nit: Clarify this comment with the new design

libc/test/src/stdlib/StrtolTest.h

 //===-- A template class for testing strto* functions -----------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/CPP/limits.h"
 #include "src/__support/CPP/type_traits.h"
+#include "src/__support/macros/properties/architectures.h"
 #include "src/errno/libc_errno.h"
 #include "test/UnitTest/Test.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 using __llvm_libc::cpp::is_signed_v;
 
void MessyBaseTenDecode(FunctionT func) {
     const char *just_space_and_sign = " +";
     libc_errno = 0;
     ASSERT_EQ(func(just_space_and_sign, &str_end, 10), ReturnT(0));
     ASSERT_EQ(libc_errno, 0);
     EXPECT_EQ(str_end - just_space_and_sign, ptrdiff_t(0));
   }
 
   void DecodeInOtherBases(FunctionT func) {
+    // This test is excessively slow on the GPU, so we limit the innermost loop.
+#if defined(LIBC_TARGET_ARCH_IS_GPU)
+    constexpr int limit = 0;
+#else
+    constexpr int limit = 36;
+#endif
     char small_string[4] = {'\0', '\0', '\0', '\0'};
     for (int base = 2; base <= 36; ++base) {
       for (int first_digit = 0; first_digit <= 36; ++first_digit) {
         small_string[0] = int_to_b36_char(first_digit);
         if (first_digit < base) {
           libc_errno = 0;
           ASSERT_EQ(func(small_string, nullptr, base),
                     static_cast<ReturnT>(first_digit));
for (int base = 2; base <= 36; ++base) {
       }
     }
 
     for (int base = 2; base <= 36; ++base) {
       for (int first_digit = 0; first_digit <= 36; ++first_digit) {
         small_string[0] = int_to_b36_char(first_digit);
         for (int second_digit = 0; second_digit <= 36; ++second_digit) {
           small_string[1] = int_to_b36_char(second_digit);
-          for (int third_digit = 0; third_digit <= 36; ++third_digit) {
+          for (int third_digit = 0; third_digit <= limit; ++third_digit) {
             small_string[2] = int_to_b36_char(third_digit);
 
             if (first_digit < base && second_digit < base &&
                 third_digit < base) {
               libc_errno = 0;
               ASSERT_EQ(func(small_string, nullptr, base),
                         static_cast<ReturnT>(third_digit +
                                              (second_digit * base) +