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[C2y] Add conformance test for WG14 N3364 #115332

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Merged
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Nov 7, 2024
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[C2y] Add conformance test for WG14 N3364 #115332

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5 changes: 5 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -286,6 +286,11 @@ C2y Feature Support
language modes but is now rejected (all of the other qualifiers and storage
class specifiers were previously rejected).

- Updated conformance for `N3364 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3364.pdf>`_
on floating-point translation-time initialization with signaling NaN. This
paper adopts Clang's existing practice, so there were no changes to compiler
behavior.

C23 Feature Support
^^^^^^^^^^^^^^^^^^^

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35 changes: 35 additions & 0 deletions clang/test/C/C2y/n3364.c
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@@ -0,0 +1,35 @@
// RUN: %clang_cc1 -verify -std=c2y -Wall -pedantic -emit-llvm -o - %s
// RUN: %clang_cc1 -verify -Wall -pedantic -emit-llvm -o - %s
// expected-no-diagnostics

/* WG14 N3364: Yes
* Give consistent wording for SNAN initialization v3
*
* Ensure that initializing from a signaling NAN (optionally with a unary + or
* -) at translation time behaves correctly at runtime.
*/

#define FLT_SNAN __builtin_nansf("1")
#define DBL_SNAN __builtin_nans("1")
#define LD_SNAN __builtin_nansl("1")

float f1 = FLT_SNAN;
float f2 = +FLT_SNAN;
float f3 = -FLT_SNAN;
// CHECK: @f1 = {{.*}}global float 0x7FF0000020000000
// CHECK: @f2 = {{.*}}global float 0x7FF0000020000000
// CHECK: @f3 = {{.*}}global float 0xFFF0000020000000

double d1 = DBL_SNAN;
double d2 = +DBL_SNAN;
double d3 = -DBL_SNAN;
// CHECK: @d1 = {{.*}}global double 0x7FF0000000000001
// CHECK: @d2 = {{.*}}global double 0x7FF0000000000001
// CHECK: @d3 = {{.*}}global double 0xFFF0000000000001

long double ld1 = LD_SNAN;
long double ld2 = +LD_SNAN;
long double ld3 = -LD_SNAN;
// CHECK: @ld1 = {{.*}}global {{double 0x7FF0000000000001|x86_fp80 0xK7FFF8000000000000001|fp128 0xL00000000000000017FFF000000000000}}
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@jcranmer-intel : I recall seeing in the past that we sometimes print floats as scientific notation. Is this/the above in danger in any way because of it?

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These are sNaN values, which can't be emitted as a regular decimal floating-point literals. There is an outstanding patch right now to emit NaNs and infinities not in this special hexadecimal syntax (instead something like nan(u0x1), syntax still somewhat TBD), but I would assume such a patch would adjust these test results as necessary.

// CHECK: @ld2 = {{.*}}global {{double 0x7FF0000000000001|x86_fp80 0xK7FFF8000000000000001|fp128 0xL00000000000000017FFF000000000000}}
// CHECK: @ld3 = {{.*}}global {{double 0xFFF0000000000001|x86_fp80 0xKFFFF8000000000000001|fp128 0xL0000000000000001FFFF000000000000}}
2 changes: 1 addition & 1 deletion clang/www/c_status.html
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Expand Up @@ -231,7 +231,7 @@ <h2 id="c2y">C2y implementation status</h2>
<tr>
<td>Give consistent wording for SNAN initialization v3</td>
<td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3364.pdf">N3364</a></td>
<td class="unknown" align="center">Unknown</td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td>Case range expressions v3.1</td>
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