[libc-commits] [libc] [libc] Fix linking of AMDGPU device runtime control constants for math (PR #65676)

Thu Sep 7 14:13:09 PDT 2023

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/65676:

Summary:
Currently, `libc` temporarily provides math by linking against existing
vendor implementations. To use the AMDGPU DeviceRTL we need to define a
handful of control constants that alter behaviour for architecture
specific things. Previously these were marked `extern const` because
they must be present when we link-in the vendor bitcode library.
However, this causes linker errors if more than one math function was
used.

This patch fixes the issue by marking these functions as used and inline
on top of being external. This means that they are linkable, but it
gives us `linkonce_odr` semantics. The downside is that these globals
won't be optimized out, but it allows us to perform constant propagation
on them unlike using `weak`.


>From 048c9c988e56e5673837405f15447b09d7d9e972 Mon Sep 17 00:00:00 2001
From: Joseph Huber <jhuber6 at vols.utk.edu>
Date: Thu, 7 Sep 2023 16:08:30 -0500
Subject: [PATCH] [libc] Fix linking of AMDGPU device runtime control constants
 for math

Summary:
Currently, `libc` temporarily provides math by linking against existing
vendor implementations. To use the AMDGPU DeviceRTL we need to define a
handful of control constants that alter behaviour for architecture
specific things. Previously these were marked `extern const` because
they must be present when we link-in the vendor bitcode library.
However, this causes linker errors if more than one math function was
used.

This patch fixes the issue by marking these functions as used and inline
on top of being external. This means that they are linkable, but it
gives us `linkonce_odr` semantics. The downside is that these globals
won't be optimized out, but it allows us to perform constant propagation
on them unlike using `weak`.
---
 libc/src/math/gpu/vendor/amdgpu/platform.h | 82 +++++++++++-----------
 1 file changed, 41 insertions(+), 41 deletions(-)

diff --git a/libc/src/math/gpu/vendor/amdgpu/platform.h b/libc/src/math/gpu/vendor/amdgpu/platform.h
index 6ec47c24a93a2d7..429c6b16a40a5ef 100644
--- a/libc/src/math/gpu/vendor/amdgpu/platform.h
+++ b/libc/src/math/gpu/vendor/amdgpu/platform.h
@@ -19,91 +19,91 @@ namespace __llvm_libc {
 extern "C" {
 
 // Disable unsafe math optimizations in the implementation.
-extern const uint8_t __oclc_unsafe_math_opt = 0;
+[[gnu::used]] extern const inline uint8_t __oclc_unsafe_math_opt = 0;
 
 // Disable denormalization at zero optimizations in the implementation.
-extern const uint8_t __oclc_daz_opt = 0;
+[[gnu::used]] extern const inline uint8_t __oclc_daz_opt = 0;
 
 // Disable rounding optimizations for 32-bit square roots.
-extern const uint8_t __oclc_correctly_rounded_sqrt32 = 1;
+[[gnu::used]] extern const inline uint8_t __oclc_correctly_rounded_sqrt32 = 1;
 
 // Disable finite math optimizations.
-extern const uint8_t __oclc_finite_only_opt = 0;
+[[gnu::used]] extern const inline uint8_t __oclc_finite_only_opt = 0;
 
 #if defined(__gfx700__)
-extern const uint32_t __oclc_ISA_version = 7000;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7000;
 #elif defined(__gfx701__)
-extern const uint32_t __oclc_ISA_version = 7001;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7001;
 #elif defined(__gfx702__)
-extern const uint32_t __oclc_ISA_version = 7002;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7002;
 #elif defined(__gfx703__)
-extern const uint32_t __oclc_ISA_version = 7003;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7003;
 #elif defined(__gfx704__)
-extern const uint32_t __oclc_ISA_version = 7004;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7004;
 #elif defined(__gfx705__)
-extern const uint32_t __oclc_ISA_version = 7005;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 7005;
 #elif defined(__gfx801__)
-extern const uint32_t __oclc_ISA_version = 8001;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 8001;
 #elif defined(__gfx802__)
-extern const uint32_t __oclc_ISA_version = 8002;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 8002;
 #elif defined(__gfx803__)
-extern const uint32_t __oclc_ISA_version = 8003;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 8003;
 #elif defined(__gfx805__)
-extern const uint32_t __oclc_ISA_version = 8005;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 8005;
 #elif defined(__gfx810__)
-extern const uint32_t __oclc_ISA_version = 8100;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 8100;
 #elif defined(__gfx900__)
-extern const uint32_t __oclc_ISA_version = 9000;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9000;
 #elif defined(__gfx902__)
-extern const uint32_t __oclc_ISA_version = 9002;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9002;
 #elif defined(__gfx904__)
-extern const uint32_t __oclc_ISA_version = 9004;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9004;
 #elif defined(__gfx906__)
-extern const uint32_t __oclc_ISA_version = 9006;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9006;
 #elif defined(__gfx908__)
-extern const uint32_t __oclc_ISA_version = 9008;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9008;
 #elif defined(__gfx909__)
-extern const uint32_t __oclc_ISA_version = 9009;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9009;
 #elif defined(__gfx90a__)
-extern const uint32_t __oclc_ISA_version = 9010;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9010;
 #elif defined(__gfx90c__)
-extern const uint32_t __oclc_ISA_version = 9012;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9012;
 #elif defined(__gfx940__)
-extern const uint32_t __oclc_ISA_version = 9400;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 9400;
 #elif defined(__gfx1010__)
-extern const uint32_t __oclc_ISA_version = 10100;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10100;
 #elif defined(__gfx1011__)
-extern const uint32_t __oclc_ISA_version = 10101;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10101;
 #elif defined(__gfx1012__)
-extern const uint32_t __oclc_ISA_version = 10102;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10102;
 #elif defined(__gfx1013__)
-extern const uint32_t __oclc_ISA_version = 10103;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10103;
 #elif defined(__gfx1030__)
-extern const uint32_t __oclc_ISA_version = 10300;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10300;
 #elif defined(__gfx1031__)
-extern const uint32_t __oclc_ISA_version = 10301;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10301;
 #elif defined(__gfx1032__)
-extern const uint32_t __oclc_ISA_version = 10302;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10302;
 #elif defined(__gfx1033__)
-extern const uint32_t __oclc_ISA_version = 10303;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10303;
 #elif defined(__gfx1034__)
-extern const uint32_t __oclc_ISA_version = 10304;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10304;
 #elif defined(__gfx1035__)
-extern const uint32_t __oclc_ISA_version = 10305;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10305;
 #elif defined(__gfx1036__)
-extern const uint32_t __oclc_ISA_version = 10306;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 10306;
 #elif defined(__gfx1100__)
-extern const uint32_t __oclc_ISA_version = 11000;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11000;
 #elif defined(__gfx1101__)
-extern const uint32_t __oclc_ISA_version = 11001;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11001;
 #elif defined(__gfx1102__)
-extern const uint32_t __oclc_ISA_version = 11002;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11002;
 #elif defined(__gfx1103__)
-extern const uint32_t __oclc_ISA_version = 11003;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11003;
 #elif defined(__gfx1150__)
-extern const uint32_t __oclc_ISA_version = 11500;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11500;
 #elif defined(__gfx1151__)
-extern const uint32_t __oclc_ISA_version = 11501;
+[[gnu::used]] extern const inline uint32_t __oclc_ISA_version = 11501;
 #else
 #error "Unknown AMDGPU architecture"
 #endif

