[lld] 2028fe6 - [lld-macho] Handle LOH_ARM64_ADRP_LDR_GOT optimization hints

[Daniel Bertalan via llvm-commits]

Author: Daniel Bertalan
Date: 2022-07-05T07:33:13+02:00
New Revision: 2028fe6fbca6ba03a4be85f733f2332016566c58

URL: https://github.com/llvm/llvm-project/commit/2028fe6fbca6ba03a4be85f733f2332016566c58
DIFF: https://github.com/llvm/llvm-project/commit/2028fe6fbca6ba03a4be85f733f2332016566c58.diff

LOG: [lld-macho] Handle LOH_ARM64_ADRP_LDR_GOT optimization hints

This hint instructs the linker to perform the AdrpLdr or AdrpAdd
transformation depending on whether the GOT load has been relaxed to
load a local symbol's address.

Differential Revision: https://reviews.llvm.org/D129059

Added: 
    lld/test/MachO/loh-adrp-ldr-got.s

Modified: 
    lld/MachO/Arch/ARM64.cpp

Removed: 
    


################################################################################
diff  --git a/lld/MachO/Arch/ARM64.cpp b/lld/MachO/Arch/ARM64.cpp
index 7064df5793aa7..7c2b7bdfe0571 100644
--- a/lld/MachO/Arch/ARM64.cpp
+++ b/lld/MachO/Arch/ARM64.cpp
@@ -189,6 +189,7 @@ class OptimizationHintContext {
   void applyAdrpAdd(const OptimizationHint &);
   void applyAdrpAdrp(const OptimizationHint &);
   void applyAdrpLdr(const OptimizationHint &);
+  void applyAdrpLdrGot(const OptimizationHint &);
 
 private:
   uint8_t *buf;
@@ -424,6 +425,19 @@ void OptimizationHintContext::applyAdrpLdr(const OptimizationHint &hint) {
   writeLiteralLdr(buf + hint.offset0 + hint.delta[0], ldr, delta);
 }
 
+// GOT loads are emitted by the compiler as a pair of adrp and ldr instructions,
+// but they may be changed to adrp+add by relaxGotLoad(). This hint performs
+// the AdrpLdr or AdrpAdd transformation depending on whether it was relaxed.
+void OptimizationHintContext::applyAdrpLdrGot(const OptimizationHint &hint) {
+  uint32_t ins2 = read32le(buf + hint.offset0 + hint.delta[0]);
+  Add add;
+  Ldr ldr;
+  if (parseAdd(ins2, add))
+    applyAdrpAdd(hint);
+  else if (parseLdr(ins2, ldr))
+    applyAdrpLdr(hint);
+}
+
 void ARM64::applyOptimizationHints(uint8_t *buf, const ConcatInputSection *isec,
                                    ArrayRef<uint64_t> relocTargets) const {
   assert(isec);
@@ -452,7 +466,7 @@ void ARM64::applyOptimizationHints(uint8_t *buf, const ConcatInputSection *isec,
       ctx1.applyAdrpAdd(hint);
       break;
     case LOH_ARM64_ADRP_LDR_GOT:
-      // TODO: Implement this as well
+      ctx1.applyAdrpLdrGot(hint);
       break;
     }
   }

diff  --git a/lld/test/MachO/loh-adrp-ldr-got.s b/lld/test/MachO/loh-adrp-ldr-got.s
new file mode 100644
index 0000000000000..5363a11677704
--- /dev/null
+++ b/lld/test/MachO/loh-adrp-ldr-got.s
@@ -0,0 +1,35 @@
+# REQUIRES: aarch64
+
+# RUN: rm -rf %t; split-file %s %t
+# RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin %t/obj.s -o %t/obj.o
+# RUN: llvm-mc -filetype=obj -triple=arm64-apple-darwin %t/dylib.s -o %t/dylib.o
+# RUN: %lld -arch arm64 -dylib -o %t/libdylib.dylib %t/dylib.o
+# RUN: %lld -arch arm64 %t/obj.o %t/libdylib.dylib -o %t/AdrpLdrGot
+# RUN: llvm-objdump -d --macho %t/AdrpLdrGot | FileCheck %s
+
+#--- obj.s
+.text
+.globl _main
+# CHECK-LABEL: _main:
+_main:
+## The referenced symbol is local
+L1: adrp x0, _local at GOTPAGE
+L2: ldr  x0, [x0, _local at GOTPAGEOFF]
+# CHECK-NEXT: adr x0
+# CHECK-NEXT: nop
+
+## The referenced symbol is in a dylib
+L3: adrp x1, _external at GOTPAGE
+L4: ldr  x1, [x1, _external at GOTPAGEOFF]
+# CHECK-NEXT: nop
+# CHECK-NEXT: ldr x1
+
+_local:
+  nop
+
+.loh AdrpLdrGot L1, L2
+.loh AdrpLdrGot L3, L4
+
+#--- dylib.s
+.globl _external
+_external: