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File 1144-x86-jit-Use-erlang-style-name-arity-for-labels-in-as.patch of Package erlang (Revision de16d5bb9b1e73f72aa79d2ecdf361ff)

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From 68ff8d95570867166e4023e725bcbbd19c9ce843 Mon Sep 17 00:00:00 2001
From: Frej Drejhammar <frej.drejhammar@gmail.com>
Date: Fri, 18 Jun 2021 09:19:07 +0200
Subject: [PATCH 4/7] x86-jit: Use erlang-style <name>/<arity> for labels in
 asm dump

When running with `+JDdump true` the most verbose x86-assembly dump is
produced by the debug emulator. In it, labels present in the
beam-assembly are printed as `label_<index>`. This patch improves the
readability of the x86-assembly dumps by pretty-printing the label
marking the start of a function using its <name>/<arity> Erlang name.

Previously pretty-printing in the `label_<index>` format was only
available in the debug emulator. Readability and the ease with which a
user can cross-correlate x86-assembly and beam-assembly dumps is
significantly improved with pretty-printed labels, thus this patch
enables the functionality as soon as `+JDdump true` is enabled.
---
 .../emulator/beam/jit/x86/beam_asm_module.cpp | 46 +++++++++++++++----
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/erts/emulator/beam/jit/x86/beam_asm_module.cpp b/erts/emulator/beam/jit/x86/beam_asm_module.cpp
index 6f062be001..5627b44603 100644
--- a/erts/emulator/beam/jit/x86/beam_asm_module.cpp
+++ b/erts/emulator/beam/jit/x86/beam_asm_module.cpp
@@ -86,18 +86,44 @@ BeamModuleAssembler::BeamModuleAssembler(BeamGlobalAssembler *ga,
     this->mod = mod;
 
     labels.reserve(num_labels + 1);
-    for (unsigned i = 1; i < num_labels; i++) {
-        Label lbl;
-
-#ifdef DEBUG
-        std::string lblName = "label_" + std::to_string(i);
-        lbl = a.newNamedLabel(lblName.data());
-#else
-        lbl = a.newLabel();
-#endif
 
-        labels[i] = lbl;
+    if (erts_jit_asm_dump && named_labels) {
+        BeamFile_ExportEntry *e = &named_labels->entries[0];
+        for (unsigned i = 1; i < num_labels; i++) {
+            Label lbl;
+            char tmp[512]; // Large enough to hold most realistic
+                           // function names. We will truncate too
+                           // long names, but as the label name is not
+                           // important for the functioning of asmjit
+                           // and this functionality is probably only
+                           // used by developers, we don't bother with
+                           // dynamic allocation.
+            // The named_labels are sorted, so no need for a search.
+            if ((unsigned)e->label == i) {
+                erts_snprintf(tmp, sizeof(tmp), "%T/%d", e->function, e->arity);
+                lbl = a.newNamedLabel(tmp);
+                e++;
+            } else {
+                std::string lblName = "label_" + std::to_string(i);
+                lbl = a.newNamedLabel(lblName.data());
+            }
+            labels[i] = lbl;
+        }
+        return;
+    }
+    if (erts_jit_asm_dump) {
+        // There is no naming info, but dumping of the assembly code
+        // has been requested, so do the best we can and number the
+        // labels.
+        for (unsigned i = 1; i < num_labels; i++) {
+            std::string lblName = "label_" + std::to_string(i);
+            labels[i] = a.newNamedLabel(lblName.data());
+        }
+        return;
     }
+    // No output is requested, go with unnamed labels
+    for (unsigned i = 1; i < num_labels; i++)
+        labels[i] = a.newLabel();
 }
 
 BeamModuleAssembler::BeamModuleAssembler(BeamGlobalAssembler *ga,
-- 
2.26.2

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