[flang-commits] [flang] [flang][NFC] document BOZ error in DIM, MOD, MODULO, and SIGN (PR #87779)

[via flang-commits]

https://github.com/jeanPerier created https://github.com/llvm/llvm-project/pull/87779

It is highly ambiguous to what type BOZ should be resolved in DIM, MOD, MODULO, and SIGN intrinsic arguments. Some other compilers accept them, but none agree. See table below.

List them explicitly as non supported extensions (semantics already reject them, this is an NFC).

Table listing the resolved types of the intrinsic results when there is a BOZ argument:

|                     | gfortran | nvfortran | ifort | nagfor | xlf    |
| ------------------- | -------- | --------- | ----- | ------ | ------ |
|  DIM(INT4, BOZ)     |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  DIM(BOZ, REAL4)    | error    |  INT8     | error | error  |  REAL4 |
|  DIM(REAL4, BOZ)    | error    |  REAL4    | error | error  |  REAL4 |
|  DIM(BOZ, INT4)     |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  DIM(BOZ, BOZ)      |  INT16   |  INT8     |  INT8 | INT8   |  REAL4 |
|  MOD(INT4, BOZ)     |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  MOD(BOZ, REAL4)    | error    |  INT8     | error | error  |  REAL4 |
|  MOD(REAL4, BOZ)    | error    |  REAL4    | error | error  |  REAL4 |
|  MOD(BOZ, INT4)     |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MOD(BOZ, BOZ)      |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MODULO(INT4, BOZ)  |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  MODULO(BOZ, REAL4) | error    |  INT8     | error | error  |  REAL4 |
|  MODULO(REAL4, BOZ) | error    |  REAL4    | error | error  |  REAL4 |
|  MODULO(BOZ, INT4)  |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MODULO(BOZ, BOZ)   |  INT16   |  INT8     |  INT8 | INT8   |  INT8  |
|  SIGN(INT4, BOZ)    | error    |  INT4     |  INT8 | INT4   |  INT4  |
|  SIGN(BOZ, REAL4)   | error    |  INT8     | error | error  |  REAL4 |
|  SIGN(REAL4, BOZ)   | error    |  REAL4    | error | error  |  REAL4 |
|  SIGN(BOZ, INT4)    | error    |  INT8     |  INT8 | INT8   |  INT4  |
|  SIGN(BOZ, BOZ)     |  INT16   |  INT8     |  INT8 | INT8   |  REAL4 |

>From 388264bc99c4ce6d03a277fb0fcb4c0be46b7535 Mon Sep 17 00:00:00 2001
From: Jean Perier <jperier at nvidia.com>
Date: Fri, 5 Apr 2024 05:58:25 -0700
Subject: [PATCH] [flang][NFC] document BOZ error in DIM, MOD, MODULO, and SIGN

It is highly ambiguous to what type BOZ should be resolved in DIM, MOD, MODULO,
and SIGN intrinsic arguments. Some other compilers accept them, but none agree.
See table below.

List them explicitly as non supported extensions (semantics already reject
them, this is an NFC).

Table listing the resolved types of the intrinsic results when there is a BOZ
argument:

|                     | gfortran | nvfortran | ifort | nagfor | xlf    |
| ------------------- | -------- | --------- | ----- | ------ | ------ |
|  DIM(INT4, BOZ)     |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  DIM(BOZ, REAL4)    | error    |  INT8     | error | error  |  REAL4 |
|  DIM(REAL4, BOZ)    | error    |  REAL4    | error | error  |  REAL4 |
|  DIM(BOZ, INT4)     |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  DIM(BOZ, BOZ)      |  INT16   |  INT8     |  INT8 | INT8   |  REAL4 |
|  MOD(INT4, BOZ)     |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  MOD(BOZ, REAL4)    | error    |  INT8     | error | error  |  REAL4 |
|  MOD(REAL4, BOZ)    | error    |  REAL4    | error | error  |  REAL4 |
|  MOD(BOZ, INT4)     |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MOD(BOZ, BOZ)      |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MODULO(INT4, BOZ)  |  INT16   |  INT4     |  INT8 | crash  |  INT4  |
|  MODULO(BOZ, REAL4) | error    |  INT8     | error | error  |  REAL4 |
|  MODULO(REAL4, BOZ) | error    |  REAL4    | error | error  |  REAL4 |
|  MODULO(BOZ, INT4)  |  INT16   |  INT8     |  INT8 | INT8   |  INT4  |
|  MODULO(BOZ, BOZ)   |  INT16   |  INT8     |  INT8 | INT8   |  INT8  |
|  SIGN(INT4, BOZ)    | error    |  INT4     |  INT8 | INT4   |  INT4  |
|  SIGN(BOZ, REAL4)   | error    |  INT8     | error | error  |  REAL4 |
|  SIGN(REAL4, BOZ)   | error    |  REAL4    | error | error  |  REAL4 |
|  SIGN(BOZ, INT4)    | error    |  INT8     |  INT8 | INT8   |  INT4  |
|  SIGN(BOZ, BOZ)     |  INT16   |  INT8     |  INT8 | INT8   |  REAL4 |
---
 flang/docs/Extensions.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
index 697bd131c04c7a..d44242de17d567 100644
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -193,7 +193,9 @@ end
   converted.  BOZ literals are interpreted as default INTEGER only
   when they appear as the first items of array constructors with no
   explicit type.  Otherwise, they generally cannot be used if the type would
-  not be known (e.g., `IAND(X'1',X'2')`).
+  not be known (e.g., `IAND(X'1',X'2')`, or as arguments of `DIM`, `MOD`,
+  `MODULO`, and `SIGN`. Note that while other compilers may accept such usages,
+  the type resolution of such BOZ literals usages is highly non portable).
 * BOZ literals can also be used as REAL values in some contexts where the
   type is unambiguous, such as initializations of REAL parameters.
 * EQUIVALENCE of numeric and character sequences (a ubiquitous extension),