Fix missing builtins in C programs linking with compiler_builtins (#17475)

programs/bpf/c/src/float/float.c

@@ -0,0 +1,19 @@
+/**
+ * @brief Example C based BPF program that performs operations
+ * on floating point values.  The test fails if floating point
+ * emulation functions were not linked to the module.
+ */
+#include <solana_sdk.h>
+
+extern uint64_t entrypoint(const uint8_t *input) {
+  SolAccountInfo ka[1];
+  SolParameters params = (SolParameters) { .ka = ka };
+
+  if (!sol_deserialize(input, &params, SOL_ARRAY_SIZE(ka))) {
+    return ERROR_INVALID_ARGUMENT;
+  }
+  uint32_t *data = (uint32_t *)(params.ka[0].data);
+  *data += 1.5;
+
+  return SUCCESS;
+}

programs/bpf/tests/programs.rs

@@ -431,6 +431,7 @@ fn test_program_bpf_sanity() {
         programs.extend_from_slice(&[
             ("alloc", true),
             ("bpf_to_bpf", true),
+            ("float", true),
             ("multiple_static", true),
             ("noop", true),
             ("noop++", true),

sdk/bpf/c/bpf.mk

@@ -15,7 +15,8 @@ OUT_DIR ?= ./out
 OS := $(shell uname)
 
 LLVM_DIR = $(LOCAL_PATH)../dependencies/bpf-tools/llvm
-LLVM_SYSTEM_INC_DIRS := $(LLVM_DIR)/lib/clang/11.0.1/include
+LLVM_SYSTEM_INC_DIRS := $(LLVM_DIR)/lib/clang/12.0.1/include
+COMPILER_RT_DIR = $(LOCAL_PATH)../dependencies/bpf-tools/rust/lib/rustlib/bpfel-unknown-unknown/lib
 
 ifdef LLVM_DIR
 CC := $(LLVM_DIR)/bin/clang
@@ -167,7 +168,7 @@ define SO_RULE
 $1: $2
 	@echo "[lld] $1 ($2)"
 	$(_@)mkdir -p $(dir $1)
-	$(_@)$(LLD) $(BPF_LLD_FLAGS) -o $1 $2
+	$(_@)$(LLD) $(BPF_LLD_FLAGS) -o $1 $2 $(COMPILER_RT_DIR)/libcompiler_builtins-*.rlib
 ifeq (,$(wildcard $(subst .so,-keypair.json,$1)))
 	$(_@)solana-keygen new --no-passphrase --silent -o $(subst .so,-keypair.json,$1)
 endif