[gcn] install.texi: Update for new ISA targets and their requirements

GCN now supports several additional ISA targets such that no longer
all targets have a multilib by default; add a note about this, the
generic targets and the required LLVM (and ROCm) versions.

gcc/ChangeLog:

	* doc/install.texi (GCN): Update section about multilibs and
	required LLVM version.

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 3b9f56b052925fd8f89d5ffa92d453dd0bad95f8..d6cf318b3afefa0bdb6cab289a9c9bebb87e58ca 100644 (file)
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -3991,14 +3991,36 @@ This is a synonym for @samp{x86_64-*-solaris2*}.
 @heading amdgcn-*-amdhsa
 AMD GCN GPU target.
 
-Instead of GNU Binutils, you will need to install LLVM 15, or later, and copy
+Instead of GNU Binutils, you need to install LLVM and copy
 @file{bin/llvm-mc} to @file{amdgcn-amdhsa/bin/as},
 @file{bin/lld} to @file{amdgcn-amdhsa/bin/ld},
 @file{bin/llvm-nm} to @file{amdgcn-amdhsa/bin/nm}, and
 @file{bin/llvm-ar} to both @file{bin/amdgcn-amdhsa-ar} and
-@file{bin/amdgcn-amdhsa-ranlib}.  Note that LLVM 13.0.1 or LLVM 14 can be used
-by specifying a @code{--with-multilib-list=} that does not list @code{gfx1100}
-and @code{gfx1103}.
+@file{bin/amdgcn-amdhsa-ranlib}.
+
+The required version of LLVM depends on the devices that you want to support.
+As the list of ISAs is long, GCC by default only builds a subset of the
+supported ISAs as multilib; use @code{--with-multilib-list=} to tailor the built
+multilibs.  Note that mixing ISAs in the same binary is not supported and gives
+a linker error.
+
+By default, multilib support is built for @code{gfx900}, @code{gfx906},
+@code{gfx908}, @code{gfx90a}, @code{gfx90c}, @code{gfx1030}, @code{gfx1036},
+@code{gfx1100} and @code{gfx1103}.  The default multilib configuration
+requires LLVM 15 or newer.  LLVM 13.0.1 or LLVM 14 can be used by specifying
+a @code{--with-multilib-list=} that does not list any GFX 11 device nor
+@code{gfx1036}.  At least LLVM 16 is required for @code{gfx1150} and
+@code{gfx1151}, LLVM 19 for the generic @code{gfx9-generic},
+@code{gfx10-3-generic}, and @code{gfx11-generic} targets and for
+@code{gfx1152}, while LLVM 20 is required for @code{gfx1153}.
+
+The supported ISA architectures are listed in the GCC manual. The generic
+ISA targets @code{gfx9-generic}, @code{gfx10-3-generic}, and
+@code{gfx11-generic} reduce the number of required multilibs but note
+that @code{gfx9-generic} does not include @code{gfx908} or @code{gfx90a},
+that linking specific ISA code with generic code is currently not supported,
+and that only a future ROCm release (newer than 6.3.2) will be able to execute
+generic code.
 
 Use Newlib (4.3.0 or newer; 4.4.0 contains some improvements and 4.5.0 fixes
 the device console output for GFX10 and GFX11 devices).