File llvm-skip-broken-float-test.patch of Package llvm7.23724

From: Petr Tesarik <ptesarik@suse.com>
Subject: Skip broken floating-point tests on i586
References: bsc#1145085
Patch-mainline: not yet, needs further research

The test suite fails like this on i586:

 [ 1254s] FAIL: LLVM-Unit :: Support/./SupportTests/JSONTest.Integers (2436 of 27030)
 [ 1254s] ******************** TEST 'LLVM-Unit :: Support/./SupportTests/JSONTest.Integers' FAILED ********************
 [ 1254s] Note: Google Test filter = JSONTest.Integers
 [ 1254s] [==========] Running 1 test from 1 test case.
 [ 1254s] [----------] Global test environment set-up.
 [ 1254s] [----------] 1 test from JSONTest
 [ 1254s] [ RUN ] JSONTest.Integers
 [ 1254s] ../unittests/Support/JSONTest.cpp:319: Failure
 [ 1254s] Expected: Doc->getAsNumber()
 [ 1254s] Which is: 12-byte object <00-00 00-00 00-00 D0-43 01-38 D1-08>
 [ 1254s] To be equal to: T.AsNumber
 [ 1254s] Which is: 12-byte object <00-00 00-00 00-00 D0-43 01-B0 92-F2>
 [ 1254s] Integer, not exact double. Stored as int64, convertible.
 [ 1254s] ../unittests/Support/JSONTest.cpp:319: Failure
 [ 1254s] Expected: Doc->getAsNumber()
 [ 1254s] Which is: 12-byte object <00-00 00-00 00-00 D0-C3 01-60 D1-08>
 [ 1254s] To be equal to: T.AsNumber
 [ 1254s] Which is: 12-byte object <00-00 00-00 00-00 D0-C3 01-00 00-00>
 [ 1254s] Negative integer, not exact double. Stored as int64, convertible.
 [ 1254s] [ FAILED ] JSONTest.Integers (0 ms)
 [ 1254s] [----------] 1 test from JSONTest (0 ms total)
 [ 1254s]
 [ 1254s] [----------] Global test environment tear-down
 [ 1254s] [==========] 1 test from 1 test case ran. (1 ms total)
 [ 1254s] [ PASSED ] 0 tests.
 [ 1254s] [ FAILED ] 1 test, listed below:
 [ 1254s] [ FAILED ] JSONTest.Integers

Essentially, there is a check that an int64_t converted to a double
matches a pre-calculated value exactly. This does not work for a
large 64-bit integer which cannot be interpreted exactly as a 64-bit
double.

That's because the integer value is stored in a hardware floating-point
register (using the FILD instruction). This register has 80 bits, so it
can represent the integer value exactly. This register is then compared
with the 64-bit value (loaded into another 80-bit floating-point
register from memory using FLD instruction). Of course, the two do not
match.

It is not an issue on x86-64, because 64-bit XMM registers are used in
that case, so there is no extra precision. I believe this unit test is
broken, at least on i586.

Signed-off-by: Petr Tesarik <ptesarik@suse.com>
---
 unittests/Support/JSONTest.cpp |    2 ++
 1 file changed, 2 insertions(+)

--- a/unittests/Support/JSONTest.cpp
+++ b/unittests/Support/JSONTest.cpp
@@ -279,6 +279,7 @@ TEST(JSONTest, Integers) {
           1.5,
       },
 
+#ifndef __i386__
       {
           "Integer, not exact double. Stored as int64, convertible.",
           int64_t{0x4000000000000001},
@@ -294,6 +295,7 @@ TEST(JSONTest, Integers) {
           int64_t{-0x4000000000000001},
           double{-0x4000000000000000},
       },
+#endif
 
       {
           "Dynamically exact integer. Stored as double, convertible.",