[PATCH] D93157: [X86] Avoid data16 prefix for lea in x32 mode

[Harald van Dijk via Phabricator via llvm-commits]

hvdijk created this revision.
hvdijk added reviewers: craig.topper, RKSimon.
Herald added subscribers: pengfei, hiraditya.
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The ABI demands a data16 prefix for lea in 64-bit LP64 mode, but not in
64-bit ILP32 mode. In both modes this prefix would ordinarily be
ignored, but the instructions may be changed by the linker to
instructions that are affected by the prefix.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93157

Files:
  llvm/lib/Target/X86/X86MCInstLower.cpp
  llvm/test/CodeGen/X86/pic.ll


Index: llvm/test/CodeGen/X86/pic.ll
===================================================================
--- llvm/test/CodeGen/X86/pic.ll
+++ llvm/test/CodeGen/X86/pic.ll
@@ -285,6 +285,7 @@
 ; CHECK-I686-DAG:	calll	___tls_get_addr at PLT
 ; CHECK-I686-DAG:	leal	tlssrcgd at TLSGD(,%ebx), %eax
 ; CHECK-I686-DAG:	calll	___tls_get_addr at PLT
+; CHECK-X32-NOT:	data16
 ; CHECK-X32-DAG:	leaq	tlsdstgd at TLSGD(%rip), %rdi
 ; CHECK-X32-DAG:	callq	__tls_get_addr at PLT
 ; CHECK-X32-DAG:	leaq	tlsptrgd at TLSGD(%rip), %rdi
Index: llvm/lib/Target/X86/X86MCInstLower.cpp
===================================================================
--- llvm/lib/Target/X86/X86MCInstLower.cpp
+++ llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -979,6 +979,8 @@
   NoAutoPaddingScope NoPadScope(*OutStreamer);
   bool Is64Bits = MI.getOpcode() != X86::TLS_addr32 &&
                   MI.getOpcode() != X86::TLS_base_addr32;
+  bool Is64BitsLP64 = MI.getOpcode() == X86::TLS_addr64 ||
+                      MI.getOpcode() == X86::TLS_base_addr64;
   MCContext &Ctx = OutStreamer->getContext();
 
   MCSymbolRefExpr::VariantKind SRVK;
@@ -1012,7 +1014,7 @@
 
   if (Is64Bits) {
     bool NeedsPadding = SRVK == MCSymbolRefExpr::VK_TLSGD;
-    if (NeedsPadding)
+    if (NeedsPadding && Is64BitsLP64)
       EmitAndCountInstruction(MCInstBuilder(X86::DATA16_PREFIX));
     EmitAndCountInstruction(MCInstBuilder(X86::LEA64r)
                                 .addReg(X86::RDI)


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