Changeset 284868 in webkit

Timestamp:

Oct 26, 2021, 8:52:37 AM (5 years ago)

Author:

commit-queue@webkit.org

Message:

[JSC] Improve offlineasm debug annotations for Linux/ELF
​https://bugs.webkit.org/show_bug.cgi?id=232303

Patch by Xan López <Xan Lopez> on 2021-10-26
Reviewed by Mark Lam.

This patch does two things:

Add the .size and .type directives to every llint "function"
(global, llint opcode, 'glue'). This allows a debugger to tell you
in what logical function you are inside the giant chunk of code
that is the llint interpreter. So instead of something like this:

(gdb) x/5i $pc

=> 0xf5f8af60 <wasmLLIntPCRangeStart+3856>: b.n 0xf5f8af6c <wasmLLIntPCRangeStart+3868>

0xf5f8af62 <wasmLLIntPCRangeStart+3858>: ldr r2, [r7, #8]
0xf5f8af64 <wasmLLIntPCRangeStart+3860>: ldr r2, [r2, #28]
0xf5f8af66 <wasmLLIntPCRangeStart+3862>: subs r0, #16
0xf5f8af68 <wasmLLIntPCRangeStart+3864>: ldr.w r0, [r2, r0, lsl #3]

you get something like this:

(gdb) x/5i $pc

=> 0xf5f8c770 <wasm_f32_add+12>: bge.n 0xf5f8c77c <wasm_f32_add+24>

0xf5f8c772 <wasm_f32_add+14>: add.w r6, r7, r9, lsl #3
0xf5f8c776 <wasm_f32_add+18>: vldr d0, [r6]
0xf5f8c77a <wasm_f32_add+22>: b.n 0xf5f8c78c <wasm_f32_add+40>
0xf5f8c77c <wasm_f32_add+24>: ldr r2, [r7, #8]

The other change adds a local symbol (in addition to an internal
label) to all the "glue" labels. That allows wasm opcodes to be
seen by the debugger (and the user to break on them), among other
things.

• CMakeLists.txt: tell offlineasm we use the ELF binary format on Linux.
• llint/LowLevelInterpreter.cpp: emit a non-local label for "glue" labels.
• offlineasm/asm.rb: emit the .size and .type directives for every

llint "function" on ELF systems.

Location:

trunk/Source/JavaScriptCore

Files:

• CMakeLists.txt (modified) (1 diff)
• ChangeLog (modified) (1 diff)
• llint/LowLevelInterpreter.cpp (modified) (1 diff)
• offlineasm/asm.rb (modified) (5 diffs)

trunk/Source/JavaScriptCore/CMakeLists.txt

@@ -440 +440 @@
 else ()
     set(LLIntOutput LLIntAssembly.h)
+endif ()
+
+if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+    set(OFFLINE_ASM_ARGS --binary-format=ELF)
 endif ()
 

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-10-26  Xan López  <xan@igalia.com>
+
+        [JSC] Improve offlineasm debug annotations for Linux/ELF
+        https://bugs.webkit.org/show_bug.cgi?id=232303
+
+        Reviewed by Mark Lam.
+
+        This patch does two things:
+
+        Add the .size and .type directives to every llint "function"
+        (global, llint opcode, 'glue'). This allows a debugger to tell you
+        in what logical function you are inside the giant chunk of code
+        that is the llint interpreter. So instead of something like this:
+
+        (gdb) x/5i $pc
+          => 0xf5f8af60 <wasmLLIntPCRangeStart+3856>:  b.n     0xf5f8af6c <wasmLLIntPCRangeStart+3868>
+             0xf5f8af62 <wasmLLIntPCRangeStart+3858>:  ldr     r2, [r7, #8]
+             0xf5f8af64 <wasmLLIntPCRangeStart+3860>:  ldr     r2, [r2, #28]
+             0xf5f8af66 <wasmLLIntPCRangeStart+3862>:  subs    r0, #16
+             0xf5f8af68 <wasmLLIntPCRangeStart+3864>:  ldr.w   r0, [r2, r0, lsl #3]
+
+        you get something like this:
+
+        (gdb) x/5i $pc
+          => 0xf5f8c770 <wasm_f32_add+12>:      bge.n   0xf5f8c77c <wasm_f32_add+24>
+             0xf5f8c772 <wasm_f32_add+14>:      add.w   r6, r7, r9, lsl #3
+             0xf5f8c776 <wasm_f32_add+18>:      vldr    d0, [r6]
+             0xf5f8c77a <wasm_f32_add+22>:      b.n     0xf5f8c78c <wasm_f32_add+40>
+             0xf5f8c77c <wasm_f32_add+24>:      ldr     r2, [r7, #8]
+
+        The other change adds a local symbol (in addition to an internal
+        label) to all the "glue" labels. That allows wasm opcodes to be
+        seen by the debugger (and the user to break on them), among other
+        things.
+
+        * CMakeLists.txt: tell offlineasm we use the ELF binary format on Linux.
+        * llint/LowLevelInterpreter.cpp: emit a non-local label for "glue" labels.
+        * offlineasm/asm.rb: emit the .size and .type directives for every
+        llint "function" on ELF systems.
+
 2021-10-25  Yusuke Suzuki  <ysuzuki@apple.com>
 

trunk/Source/JavaScriptCore/llint/LowLevelInterpreter.cpp

@@ -491 +491 @@
     OFFLINE_ASM_LOCAL_LABEL(llint_##__opcode)
 
-#define OFFLINE_ASM_GLUE_LABEL(__opcode)   OFFLINE_ASM_LOCAL_LABEL(__opcode)
+#define OFFLINE_ASM_GLUE_LABEL(__opcode) \
+    OFFLINE_ASM_OPCODE_DEBUG_LABEL(__opcode) \
+    OFFLINE_ASM_LOCAL_LABEL(__opcode)
 
 #if CPU(ARM_THUMB2)

trunk/Source/JavaScriptCore/offlineasm/asm.rb

@@ -265 +265 @@
             end
         end
+        if $emitELFDebugDirectives
+            deferNextLabelAction {
+                putStr("    \".size #{labelName} , . - #{labelName} \\n\"")
+                putStr("    \".type #{labelName} , function \\n\"")
+            }
+        end
         @newlineSpacerState = :none # After a global label, we can use another spacer.
     end
@@ -342 +348 @@
 $options = {}
 OptionParser.new do |opts|
-    opts.banner = "Usage: asm.rb asmFile offsetsFile outputFileName [--assembler=<ASM>] [--webkit-additions-path=<path>]"
+    opts.banner = "Usage: asm.rb asmFile offsetsFile outputFileName [--assembler=<ASM>] [--webkit-additions-path=<path>] [--binary-format=<format>]"
     # This option is currently only used to specify the masm assembler
     opts.on("--assembler=[ASM]", "Specify an assembler to use.") do |assembler|
@@ -349 +355 @@
     opts.on("--webkit-additions-path=PATH", "WebKitAdditions path.") do |path|
         $options[:webkit_additions_path] = path
+    end
+    opts.on("--binary-format=FORMAT", "Specify the binary format used by the target system.") do |format|
+        $options[:binary_format] = format
     end
 end.parse!
@@ -366 +375 @@
 $emitWinAsm = isMSVC ? outputFlnm.index(".asm") != nil : false
 $commentPrefix = $emitWinAsm ? ";" : "//"
+
+# We want this in all ELF systems we support, except for C_LOOP (we'll disable it later on if we are building cloop)
+$emitELFDebugDirectives = $options.has_key?(:binary_format) && $options[:binary_format] == "ELF"
 
 inputHash =
@@ -413 +425 @@
                 $enableDebugAnnotations = false
                 $preferredCommentStartColumn = 60
+                $emitELFDebugDirectives = false
             end