Merged: Avoid compiler/LTO bug on arm

Merged: [wasm] Try to avoid LTO bug on arm
Revision: 241294fe186c126cfcc3d9bf99023b808daf7701

Merged: cpu-arm: Add noinline to cache flushing logic
Revision: e0e36ba0791624db71b92ee1bcaa3d02b6c0ab01

BUG=chromium:952759
LOG=N
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true
R=jkummerow@chromium.org

Change-Id: I15357d13a9609c1b82fa1108330b36c4bd7a95fe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1588463
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/branch-heads/7.5@{#12}
Cr-Branched-From: 35b9bf5-refs/heads/7.5.288@{#1}
Cr-Branched-From: 912b391-refs/heads/master@{#60911}

src/arm/cpu-arm.cc

@@ -19,7 +19,10 @@
 namespace v8 {
 namespace internal {
 
-void CpuFeatures::FlushICache(void* start, size_t size) {
+// The inlining of this seems to trigger an LTO bug that clobbers a register on
+// arm, see https://crbug.com/952759#c6.
+__attribute__((noinline)) void CpuFeatures::FlushICache(void* start,
+                                                        size_t size) {
 #if !defined(USE_SIMULATOR)
 #if V8_OS_QNX
   msync(start, size, MS_SYNC | MS_INVALIDATE_ICACHE);

src/wasm/wasm-code-manager.cc

@@ -718,9 +718,6 @@ std::unique_ptr<WasmCode> NativeModule::AddCodeWithCodeSpace(
     }
   }
 
-  // Flush the i-cache after relocation.
-  FlushInstructionCache(dst_code_bytes.start(), dst_code_bytes.size());
-
   std::unique_ptr<WasmCode> code{new WasmCode{
       this, index, dst_code_bytes, stack_slots, tagged_parameter_slots,
       safepoint_table_offset, handler_table_offset, constant_pool_offset,
@@ -731,6 +728,11 @@ std::unique_ptr<WasmCode> NativeModule::AddCodeWithCodeSpace(
 
   code->RegisterTrapHandlerData();
 
+  // Flush the i-cache for the region holding the relocated code.
+  // Do this last, as this seems to trigger an LTO bug that clobbers a register
+  // on arm, see https://crbug.com/952759#c6.
+  FlushInstructionCache(dst_code_bytes.start(), dst_code_bytes.size());
+
   return code;
 }