[AArch64] Disable cortex-a53-835769 when compiling for armv8.1-a or later

[davemgreen]

Any code compiled with armv8.1-a or later cannot run on a cortex-a53, so does not need to enable the 835769 errata fix. This patch disables the +fix-cortex-a53-835769 feature when the architecture is later than armv8.0-a. The command line flag -mfix_cortex_a53_835769 will still enable it.

[llvmbot]

@llvm/pr-subscribers-clang
@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-backend-aarch64

Author: David Green (davemgreen)

Changes

Any code compiled with armv8.1-a or later cannot run on a cortex-a53, so does not need to enable the 835769 errata fix. This patch disables the +fix-cortex-a53-835769 feature when the architecture is later than armv8.0-a. The command line flag -mfix_cortex_a53_835769 will still enable it.

---

Full diff: https://github.com/llvm/llvm-project/pull/170649.diff

3 Files Affected:

• (modified) clang/lib/Driver/ToolChains/Arch/AArch64.cpp (+11-6)
• (modified) clang/test/CodeGen/AArch64/fix-cortex-a53-835769.c (+8)
• (modified) clang/test/Driver/aarch64-fix-cortex-a53-835769.c (+4)

diff --git a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
index d6fb2a57539ed..087ae9201a1a0 100644
--- a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -453,13 +453,18 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
       Features.push_back("+fix-cortex-a53-835769");
     else
       Features.push_back("-fix-cortex-a53-835769");
-  } else if (Triple.isAndroid() || Triple.isOHOSFamily()) {
-    // Enabled A53 errata (835769) workaround by default on android
-    Features.push_back("+fix-cortex-a53-835769");
-  } else if (Triple.isOSFuchsia()) {
-    std::string CPU = getCPUName(D, Args, Triple);
-    if (CPU.empty() || CPU == "generic" || CPU == "cortex-a53")
+  } else if (Extensions.BaseArch &&
+             Extensions.BaseArch->Version.getMajor() == 8 &&
+             Extensions.BaseArch->Version.getMinor() == 0) {
+    if (Triple.isAndroid() || Triple.isOHOSFamily()) {
+      // Enabled A53 errata (835769) workaround by default on android, providing
+      // that the architecture allows running on a cortex-a53.
       Features.push_back("+fix-cortex-a53-835769");
+    } else if (Triple.isOSFuchsia()) {
+      std::string CPU = getCPUName(D, Args, Triple);
+      if (CPU.empty() || CPU == "generic" || CPU == "cortex-a53")
+        Features.push_back("+fix-cortex-a53-835769");
+    }
   }
 
   if (Args.getLastArg(options::OPT_mno_bti_at_return_twice))
diff --git a/clang/test/CodeGen/AArch64/fix-cortex-a53-835769.c b/clang/test/CodeGen/AArch64/fix-cortex-a53-835769.c
index baef74b4c18cc..d5a4d0d085f18 100644
--- a/clang/test/CodeGen/AArch64/fix-cortex-a53-835769.c
+++ b/clang/test/CodeGen/AArch64/fix-cortex-a53-835769.c
@@ -9,6 +9,14 @@
 // RUN:   | FileCheck --check-prefix=CHECK-YES --check-prefix=CHECK %s
 // RUN: %clang -O3 -target aarch64-linux-ohos %s -S -o- \
 // RUN:   | FileCheck --check-prefix=CHECK-YES --check-prefix=CHECK %s
+// RUN: %clang -O3 --target=aarch64-linux-androideabi -march=armv8.1-a %s -S -o- \
+// RUN:   | FileCheck --check-prefix=CHECK-NO --check-prefix=CHECK %s
+// RUN: %clang -O3 -target aarch64-linux-ohos -march=armv8.1-a %s -S -o- \
+// RUN:   | FileCheck --check-prefix=CHECK-NO --check-prefix=CHECK %s
+// RUN: %clang -O3 --target=aarch64-linux-androideabi -mcpu=cortex-a55 %s -S -o- \
+// RUN:   | FileCheck --check-prefix=CHECK-NO --check-prefix=CHECK %s
+// RUN: %clang -O3 -target aarch64-linux-ohos -mcpu=cortex-a55 %s -S -o- \
+// RUN:   | FileCheck --check-prefix=CHECK-NO --check-prefix=CHECK %s
 // RUN: %clang -O3 --target=aarch64-linux-androideabi -mfix-cortex-a53-835769 %s -S -o- \
 // RUN:   | FileCheck --check-prefix=CHECK-YES --check-prefix=CHECK %s
 // RUN: %clang -O3 --target=aarch64-linux-androideabi -mno-fix-cortex-a53-835769 %s -S -o- \
diff --git a/clang/test/Driver/aarch64-fix-cortex-a53-835769.c b/clang/test/Driver/aarch64-fix-cortex-a53-835769.c
index 84d8c1dde7a78..757e945a856e0 100644
--- a/clang/test/Driver/aarch64-fix-cortex-a53-835769.c
+++ b/clang/test/Driver/aarch64-fix-cortex-a53-835769.c
@@ -7,9 +7,13 @@
 
 // RUN: %clang --target=aarch64-linux-androideabi %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-YES %s
+// RUN: %clang --target=aarch64-linux-androideabi -march=armv8.1-a %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-DEF %s
 
 // RUN: %clang --target=aarch64-fuchsia %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-YES %s
+// RUN: %clang --target=aarch64-fuchsia -march=armv8.1-a %s -### 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-DEF %s
 
 // RUN: %clang --target=aarch64-fuchsia -mcpu=cortex-a73 %s -### 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-DEF %s

[smithp35]

This makes sense to me. I've added my approval. I'll add some reviewers associated with Android to make sure they are aware.

Will be worth giving them some time to respond.