[compiler-rt] 0ae2a41 - [compiler-rt][BF16] Provide __truncsfbf2 only when __bf16 is available

[Phoebe Wang via llvm-commits]

Author: Phoebe Wang
Date: 2022-08-10T09:13:44+08:00
New Revision: 0ae2a41d803d715975d710ec289a4bd90ca534e2

URL: https://github.com/llvm/llvm-project/commit/0ae2a41d803d715975d710ec289a4bd90ca534e2
DIFF: https://github.com/llvm/llvm-project/commit/0ae2a41d803d715975d710ec289a4bd90ca534e2.diff

LOG: [compiler-rt][BF16] Provide __truncsfbf2 only when __bf16 is available

#56854 shows a backwards compatibility problem when builtins of compiler-rt don't follow ABI. We need to prevent to fall into the trap again for BF16.

Reviewed By: bkramer

Differential Revision: https://reviews.llvm.org/D131147

Added: 
    

Modified: 
    compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
    compiler-rt/cmake/builtin-config-ix.cmake
    compiler-rt/lib/builtins/CMakeLists.txt
    compiler-rt/lib/builtins/fp_trunc.h
    compiler-rt/lib/builtins/truncsfbf2.c

Removed: 
    


################################################################################
diff  --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
index 2c9983c6a1ae3..9ece3c2c38559 100644
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -406,6 +406,8 @@ macro(darwin_add_builtin_libraries)
 
   append_list_if(COMPILER_RT_HAS_ASM_LSE -DHAS_ASM_LSE CFLAGS)
 
+  append_list_if(COMPILER_RT_HAS_BFLOAT16 -DCOMPILER_RT_HAS_BFLOAT16 CFLAGS)
+
   set(PROFILE_SOURCES ../profile/InstrProfiling.c
                       ../profile/InstrProfilingBuffer.c
                       ../profile/InstrProfilingPlatformDarwin.c

diff  --git a/compiler-rt/cmake/builtin-config-ix.cmake b/compiler-rt/cmake/builtin-config-ix.cmake
index 5aa2114fab93f..62e8281b919cf 100644
--- a/compiler-rt/cmake/builtin-config-ix.cmake
+++ b/compiler-rt/cmake/builtin-config-ix.cmake
@@ -30,6 +30,14 @@ _Float16 foo(_Float16 x) {
 "
 )
 
+builtin_check_c_compiler_source(COMPILER_RT_HAS_BFLOAT16
+"
+__bf16 foo(__bf16 x) {
+ return x;
+}
+"
+)
+
 builtin_check_c_compiler_source(COMPILER_RT_HAS_ASM_LSE
 "
 asm(\".arch armv8-a+lse\");

diff  --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 6143457cc9339..05c37930dae83 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -699,6 +699,8 @@ else ()
 
   append_list_if(COMPILER_RT_HAS_FLOAT16 -DCOMPILER_RT_HAS_FLOAT16 BUILTIN_CFLAGS)
 
+  append_list_if(COMPILER_RT_HAS_BFLOAT16 -DCOMPILER_RT_HAS_BFLOAT16 BUILTIN_CFLAGS)
+
   append_list_if(COMPILER_RT_HAS_STD_C11_FLAG -std=c11 BUILTIN_CFLAGS)
 
   # These flags would normally be added to CMAKE_C_FLAGS by the llvm

diff  --git a/compiler-rt/lib/builtins/fp_trunc.h b/compiler-rt/lib/builtins/fp_trunc.h
index 7a54564a3520a..91f614528ab3f 100644
--- a/compiler-rt/lib/builtins/fp_trunc.h
+++ b/compiler-rt/lib/builtins/fp_trunc.h
@@ -60,7 +60,7 @@ typedef uint16_t dst_rep_t;
 static const int dstSigBits = 10;
 
 #elif defined DST_BFLOAT
-typedef uint16_t dst_t;
+typedef __bf16 dst_t;
 typedef uint16_t dst_rep_t;
 #define DST_REP_C UINT16_C
 static const int dstSigBits = 7;

diff  --git a/compiler-rt/lib/builtins/truncsfbf2.c b/compiler-rt/lib/builtins/truncsfbf2.c
index 6bed116af9868..42ddab32a2f1c 100644
--- a/compiler-rt/lib/builtins/truncsfbf2.c
+++ b/compiler-rt/lib/builtins/truncsfbf2.c
@@ -6,8 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if defined(COMPILER_RT_HAS_BFLOAT16)
 #define SRC_SINGLE
 #define DST_BFLOAT
 #include "fp_trunc_impl.inc"
 
 COMPILER_RT_ABI dst_t __truncsfbf2(float a) { return __truncXfYf2__(a); }
+
+#endif