[PATCH] D28948: [XRay][AArch64] More staging for tail call support in XRay AArch64 - in compiler-rt
Serge Rogatch via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 20 05:53:13 PST 2017
rSerge created this revision.
Herald added a subscriber: aemerson.
This patch provides a trampoline for function tail exit tracing. Still, it's staging because code `1` is passed to the handler function (indicating a normal exit) instead of `2`, which would indicate tail exit. This is so until the logging part of XRay supports tail exits too.
https://reviews.llvm.org/D28948
Files:
lib/xray/xray_AArch64.cc
lib/xray/xray_trampoline_AArch64.S
Index: lib/xray/xray_trampoline_AArch64.S
===================================================================
--- lib/xray/xray_trampoline_AArch64.S
+++ lib/xray/xray_trampoline_AArch64.S
@@ -87,3 +87,54 @@
LDP X3, X4, [SP], #16
LDP X1, X2, [SP], #16
RET
+
+ /* Word-aligned function entry point */
+ .p2align 2
+ /* Let C/C++ see the symbol */
+ .global __xray_FunctionTailExit
+ .type __xray_FunctionTailExit, %function
+ /* In C++ it is void extern "C" __xray_FunctionTailExit(uint32_t FuncId)
+ with FuncId passed in W0 register. */
+__xray_FunctionTailExit:
+ /* Move the return address beyond the end of sled data. The 12 bytes of
+ data are inserted in the code of the runtime patch, between the call
+ instruction and the instruction returned into. The data contains 32
+ bits of instrumented function ID and 64 bits of the address of
+ the current trampoline. */
+ ADD X30, X30, #12
+ /* Push the registers which may be modified by the handler function */
+ STP X1, X2, [SP, #-16]!
+ STP X3, X4, [SP, #-16]!
+ STP X5, X6, [SP, #-16]!
+ STP X7, X30, [SP, #-16]!
+ /* Push the parameters of the tail called function */
+ STP Q0, Q1, [SP, #-32]!
+ STP Q2, Q3, [SP, #-32]!
+ STP Q4, Q5, [SP, #-32]!
+ STP Q6, Q7, [SP, #-32]!
+ /* Load the address of _ZN6__xray19XRayPatchedFunctionE into X1 */
+ LDR X1, =_ZN6__xray19XRayPatchedFunctionE
+ /* Load the handler function pointer into X2 */
+ LDR X2, [X1]
+ /* Handler address is nullptr if handler is not set */
+ CMP X2, #0
+ BEQ FunctionTailExit_restore
+ /* Function ID is already in W0 (the first parameter).
+ X1=2 means that we are tracing a tail exit event, but before the
+ logging part of XRay is ready, we pretend that here a normal function
+ exit happens, so we give the handler code 1 */
+ MOV X1, #1
+ /* Call the handler with 2 parameters in W0 and X1 */
+ BLR X2
+FunctionTailExit_restore:
+ /* Pop the parameters of the tail called function */
+ LDP Q6, Q7, [SP], #32
+ LDP Q4, Q5, [SP], #32
+ LDP Q2, Q3, [SP], #32
+ LDP Q0, Q1, [SP], #32
+ /* Pop the registers which may be modified by the handler function */
+ LDP X7, X30, [SP], #16
+ LDP X5, X6, [SP], #16
+ LDP X3, X4, [SP], #16
+ LDP X1, X2, [SP], #16
+ RET
Index: lib/xray/xray_AArch64.cc
===================================================================
--- lib/xray/xray_AArch64.cc
+++ lib/xray/xray_AArch64.cc
@@ -117,9 +117,7 @@
bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
- // FIXME: In the future we'd need to distinguish between non-tail exits and
- // tail exits for better information preservation.
- return patchSled(Enable, FuncId, Sled, __xray_FunctionExit);
+ return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
}
} // namespace __xray
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