tsan: make obtaining current PC faster

We obtain the current PC is all interceptors and collectively
common interceptor code contributes to overall slowdown
(in particular cheaper str/mem* functions).

The current way to obtain the current PC involves:

  4493e1:       e8 3a f3 fe ff          callq  438720 <_ZN11__sanitizer10StackTrace12GetCurrentPcEv>
  4493e9:       48 89 c6                mov    %rax,%rsi

and the called function is:

uptr StackTrace::GetCurrentPc() {
  438720:       48 8b 04 24             mov    (%rsp),%rax
  438724:       c3                      retq

The new way uses address of a local label and involves just:

  44a888:       48 8d 35 fa ff ff ff    lea    -0x6(%rip),%rsi

I am not switching all uses of StackTrace::GetCurrentPc to GET_CURRENT_PC
because it may lead some differences in produced reports and break tests.
The difference comes from the fact that currently we have PC pointing
to the CALL instruction, but the new way does not yield any code on its own
so the PC points to a random instruction in the function and symbolizing
that instruction can produce additional inlined frames (if the random
instruction happen to relate to some inlined function).

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D106046

compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.cpp

@@ -19,38 +19,6 @@
 
 namespace __sanitizer {
 
-uptr StackTrace::GetNextInstructionPc(uptr pc) {
-#if defined(__sparc__) || defined(__mips__)
-  return pc + 8;
-#elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
-  return pc + 4;
-#elif SANITIZER_RISCV64
-  // Current check order is 4 -> 2 -> 6 -> 8
-  u8 InsnByte = *(u8 *)(pc);
-  if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) {
-    // xxxxxxxxxxxbbb11 | 32 bit | bbb != 111
-    return pc + 4;
-  }
-  if ((InsnByte & 0x3) != 0x3) {
-    // xxxxxxxxxxxxxxaa | 16 bit | aa != 11
-    return pc + 2;
-  }
-  // RISC-V encoding allows instructions to be up to 8 bytes long
-  if ((InsnByte & 0x3f) == 0x1f) {
-    // xxxxxxxxxx011111 | 48 bit |
-    return pc + 6;
-  }
-  if ((InsnByte & 0x7f) == 0x3f) {
-    // xxxxxxxxx0111111 | 64 bit |
-    return pc + 8;
-  }
-  // bail-out if could not figure out the instruction size
-  return 0;
-#else
-  return pc + 1;
-#endif
-}
-
 uptr StackTrace::GetCurrentPc() {
   return GET_CALLER_PC();
 }

compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h

@@ -106,6 +106,39 @@ uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
 #endif
 }
 
+ALWAYS_INLINE
+uptr StackTrace::GetNextInstructionPc(uptr pc) {
+#if defined(__sparc__) || defined(__mips__)
+  return pc + 8;
+#elif defined(__powerpc__) || defined(__arm__) || defined(__aarch64__)
+  return pc + 4;
+#elif SANITIZER_RISCV64
+  // Current check order is 4 -> 2 -> 6 -> 8
+  u8 InsnByte = *(u8 *)(pc);
+  if (((InsnByte & 0x3) == 0x3) && ((InsnByte & 0x1c) != 0x1c)) {
+    // xxxxxxxxxxxbbb11 | 32 bit | bbb != 111
+    return pc + 4;
+  }
+  if ((InsnByte & 0x3) != 0x3) {
+    // xxxxxxxxxxxxxxaa | 16 bit | aa != 11
+    return pc + 2;
+  }
+  // RISC-V encoding allows instructions to be up to 8 bytes long
+  if ((InsnByte & 0x3f) == 0x1f) {
+    // xxxxxxxxxx011111 | 48 bit |
+    return pc + 6;
+  }
+  if ((InsnByte & 0x7f) == 0x3f) {
+    // xxxxxxxxx0111111 | 64 bit |
+    return pc + 8;
+  }
+  // bail-out if could not figure out the instruction size
+  return 0;
+#else
+  return pc + 1;
+#endif
+}
+
 // StackTrace that owns the buffer used to store the addresses.
 struct BufferedStackTrace : public StackTrace {
   uptr trace_buffer[kStackTraceMax];
@@ -196,5 +229,10 @@ static inline bool IsValidFrame(uptr frame, uptr stack_top, uptr stack_bottom) {
   uptr local_stack;                           \
   uptr sp = (uptr)&local_stack
 
+#define GET_CURRENT_PC()                                   \
+  ({                                                       \
+    this_pc:                                               \
+      StackTrace::GetNextInstructionPc((uptr) && this_pc); \
+  })
 
 #endif  // SANITIZER_STACKTRACE_H

compiler-rt/lib/tsan/rtl/tsan_interceptors.h

@@ -35,9 +35,9 @@ inline bool in_symbolizer() {
   ThreadState *thr = cur_thread();             \
   const uptr caller_pc = GET_CALLER_PC();      \
   ScopedInterceptor si(thr, #func, caller_pc); \
-    const uptr pc = StackTrace::GetCurrentPc(); \
+  const uptr pc = GET_CURRENT_PC();            \
   (void)pc;                                    \
-/**/
+  /**/
 
 #define SCOPED_TSAN_INTERCEPTOR(func, ...) \
     SCOPED_INTERCEPTOR_RAW(func, __VA_ARGS__); \

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

@@ -2157,7 +2157,7 @@ void atfork_prepare() {
   if (in_symbolizer())
     return;
   ThreadState *thr = cur_thread();
-  const uptr pc = StackTrace::GetCurrentPc();
+  const uptr pc = GET_CURRENT_PC();
   ForkBefore(thr, pc);
 }
 
@@ -2165,7 +2165,7 @@ void atfork_parent() {
   if (in_symbolizer())
     return;
   ThreadState *thr = cur_thread();
-  const uptr pc = StackTrace::GetCurrentPc();
+  const uptr pc = GET_CURRENT_PC();
   ForkParentAfter(thr, pc);
 }
 
@@ -2173,7 +2173,7 @@ void atfork_child() {
   if (in_symbolizer())
     return;
   ThreadState *thr = cur_thread();
-  const uptr pc = StackTrace::GetCurrentPc();
+  const uptr pc = GET_CURRENT_PC();
   ForkChildAfter(thr, pc);
   FdOnFork(thr, pc);
 }