File 1232-jit-Optimize-yield-tests.patch of Package erlang

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File 1232-jit-Optimize-yield-tests.patch of Package erlang (Revision 0e04b8d79a55adf8ba49c177393a4846)

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From a079fcaed1db15acf927688c17aea10fe7698554 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org>
Date: Thu, 23 Dec 2021 19:57:52 +0100
Subject: [PATCH 2/2] jit: Optimize yield tests

We no longer use `CALL` to figure out the yield address, so we may
as well get rid of it. While we're at it, we'll shrink the
instruction by branching directly into the shared fragment.

We'll use the same method on AArch64 as well as it's a bit easier
to follow.
---
 erts/emulator/beam/jit/arm/instr_common.cpp | 31 +++++++-------------
 erts/emulator/beam/jit/x86/instr_common.cpp | 32 +++++++++------------
 2 files changed, 24 insertions(+), 39 deletions(-)

diff --git a/erts/emulator/beam/jit/arm/instr_common.cpp b/erts/emulator/beam/jit/arm/instr_common.cpp
index d36c08ad75..6f64b5c1d6 100644
--- a/erts/emulator/beam/jit/arm/instr_common.cpp
+++ b/erts/emulator/beam/jit/arm/instr_common.cpp
@@ -1654,42 +1654,33 @@ void BeamModuleAssembler::emit_raw_raise() {
     mov_imm(XREG0, am_badarg);
 }
 
-static size_t TEST_YIELD_RETURN_OFFSET = sizeof(Uint32[3]);
+#define TEST_YIELD_RETURN_OFFSET                                               \
+    (BEAM_ASM_FUNC_PROLOGUE_SIZE + sizeof(Uint32[3]))
 
+/* ARG3 = currLabel */
 void BeamGlobalAssembler::emit_i_test_yield_shared() {
-    int mfa_offset = sizeof(ErtsCodeMFA) + BEAM_ASM_FUNC_PROLOGUE_SIZE;
+    a.sub(ARG2, ARG3, imm(sizeof(ErtsCodeMFA)));
+    a.add(ARG3, ARG3, imm(TEST_YIELD_RETURN_OFFSET));
 
-    /* Yield return address is in LR (x30). */
-    a.sub(ARG2, a64::x30, imm(TEST_YIELD_RETURN_OFFSET + mfa_offset));
     a.str(ARG2, arm::Mem(c_p, offsetof(Process, current)));
-
     a.ldr(ARG2, arm::Mem(ARG2, offsetof(ErtsCodeMFA, arity)));
     a.str(ARG2, arm::Mem(c_p, offsetof(Process, arity)));
 
-    a.mov(ARG3, a64::x30);
     a.b(labels[context_switch_simplified]);
 }
 
 void BeamModuleAssembler::emit_i_test_yield() {
-    Label next = a.newLabel();
-
     /* When present, this is guaranteed to be the first instruction after the
      * breakpoint trampoline. */
+    ASSERT((a.offset() - code.labelOffsetFromBase(currLabel)) ==
+           BEAM_ASM_FUNC_PROLOGUE_SIZE);
 
-#ifdef DEBUG
-    size_t startPos = a.offset();
-    ASSERT(startPos % 8 == 0);
-#endif
-
+    a.adr(ARG3, currLabel);
     a.subs(FCALLS, FCALLS, imm(1));
-    a.cond_gt().b(next);
-
-    /* We avoid using the `fragment_call` helper to ensure a constant layout,
-     * as it adds code in certain debug configurations. */
-    a.bl(resolve_fragment(ga->get_i_test_yield_shared(), disp128MB));
-    a.bind(next);
+    a.cond_le().b(resolve_fragment(ga->get_i_test_yield_shared(), disp1MB));
 
-    ASSERT(a.offset() - startPos == TEST_YIELD_RETURN_OFFSET);
+    ASSERT((a.offset() - code.labelOffsetFromBase(currLabel)) ==
+           TEST_YIELD_RETURN_OFFSET);
 }
 
 void BeamModuleAssembler::emit_i_yield() {
diff --git a/erts/emulator/beam/jit/x86/instr_common.cpp b/erts/emulator/beam/jit/x86/instr_common.cpp
index 76c4a14e48..81489df017 100644
--- a/erts/emulator/beam/jit/x86/instr_common.cpp
+++ b/erts/emulator/beam/jit/x86/instr_common.cpp
@@ -1916,19 +1916,14 @@ void BeamModuleAssembler::emit_raw_raise() {
     a.mov(getXRef(0), imm(am_badarg));
 }
 
-void BeamGlobalAssembler::emit_i_test_yield_shared() {
-    int mfa_offset = -(int)sizeof(ErtsCodeMFA) - BEAM_ASM_FUNC_PROLOGUE_SIZE;
-
-    if (erts_frame_layout == ERTS_FRAME_LAYOUT_FP_RA) {
-        /* Subtract the size of an `emit_enter_frame` sequence. */
-        mfa_offset -= 4;
-    } else {
-        ASSERT(erts_frame_layout == ERTS_FRAME_LAYOUT_RA);
-    }
+#define TEST_YIELD_RETURN_OFFSET                                               \
+    (BEAM_ASM_FUNC_PROLOGUE_SIZE + 16 +                                        \
+     (erts_frame_layout == ERTS_FRAME_LAYOUT_FP_RA ? 4 : 0))
 
-    a.add(x86::rsp, imm(8));
+/* ARG3 = return address, currLabel + TEST_YIELD_RETURN_OFFSET */
+void BeamGlobalAssembler::emit_i_test_yield_shared() {
+    int mfa_offset = -TEST_YIELD_RETURN_OFFSET - (int)sizeof(ErtsCodeMFA);
 
-    /* Yield address is in ARG3. */
     a.lea(ARG2, x86::qword_ptr(ARG3, mfa_offset));
     a.mov(x86::qword_ptr(c_p, offsetof(Process, current)), ARG2);
     a.mov(ARG2, x86::qword_ptr(ARG2, offsetof(ErtsCodeMFA, arity)));
@@ -1938,20 +1933,19 @@ void BeamGlobalAssembler::emit_i_test_yield_shared() {
 }
 
 void BeamModuleAssembler::emit_i_test_yield() {
-    Label next = a.newLabel(), entry = a.newLabel();
-
     /* When present, this is guaranteed to be the first instruction after the
      * breakpoint trampoline. */
-    ASSERT(a.offset() % 8 == 0);
+    ASSERT((a.offset() - code.labelOffsetFromBase(currLabel)) ==
+           BEAM_ASM_FUNC_PROLOGUE_SIZE);
 
     emit_enter_frame();
 
-    a.bind(entry);
+    a.lea(ARG3, x86::qword_ptr(currLabel, TEST_YIELD_RETURN_OFFSET));
     a.dec(FCALLS);
-    a.short_().jg(next);
-    a.lea(ARG3, x86::qword_ptr(entry));
-    a.call(yieldEnter);
-    a.bind(next);
+    a.jle(yieldEnter);
+
+    ASSERT((a.offset() - code.labelOffsetFromBase(currLabel)) ==
+           TEST_YIELD_RETURN_OFFSET);
 
 #if defined(JIT_HARD_DEBUG) && defined(ERLANG_FRAME_POINTERS)
     a.mov(ARG1, c_p);
-- 
2.31.1

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File 1232-jit-Optimize-yield-tests.patch of Package erlang (Revision 0e04b8d79a55adf8ba49c177393a4846)

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