Make LoopStrengthReduce smarter about hoisting things out of

loops when they can be subsumed into addressing modes.

Change X86 addressing mode check to realize that
some PIC references need an extra register.
(I believe this is correct for Linux, if not, I'm sure
someone will tell me.)

llvm-svn: 60608

2 files changed, 21 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 412a954566b..44f28d3d770 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6463,6 +6463,10 @@ bool X86TargetLowering::isLegalAddressingMode(const AddrMode &AM,
     // We can only fold this if we don't need an extra load.
     if (Subtarget->GVRequiresExtraLoad(AM.BaseGV, getTargetMachine(), false))
       return false;
+    // If BaseGV requires a register, we cannot also have a BaseReg.
+    if (Subtarget->GVRequiresRegister(AM.BaseGV, getTargetMachine(), false) &&
+        AM.HasBaseReg)
+      return false;
 
     // X86-64 only supports addr of globals in small code model.
     if (Subtarget->is64Bit()) {
diff --git a/llvm/lib/Target/X86/X86Subtarget.cpp b/llvm/lib/Target/X86/X86Subtarget.cpp
index b836471afc1..583fe8a0fbe 100644
--- a/llvm/lib/Target/X86/X86Subtarget.cpp
+++ b/llvm/lib/Target/X86/X86Subtarget.cpp
@@ -59,7 +59,23 @@ bool X86Subtarget::GVRequiresExtraLoad(const GlobalValue* GV,
       return (GV->hasDLLImportLinkage());
     }
   }
-  
+  return false;
+}
+
+/// True if accessing the GV requires a register.  This is a superset of the
+/// cases where GVRequiresExtraLoad is true.  Some variations of PIC require
+/// a register, but not an extra load.
+bool X86Subtarget::GVRequiresRegister(const GlobalValue *GV,
+                                       const TargetMachine& TM,
+                                       bool isDirectCall) const
+{
+  if (GVRequiresExtraLoad(GV, TM, isDirectCall))
+    return true;
+  // Code below here need only consider cases where GVRequiresExtraLoad
+  // returns false.
+  if (TM.getRelocationModel() == Reloc::PIC_)
+    return !isDirectCall && 
+      (GV->hasInternalLinkage() || GV->hasExternalLinkage());
   return false;
 }