[PowerPC] Use 16-byte alignment for modern cores for functions/loops

Most modern PowerPC cores prefer that functions and loops start on
16-byte-aligned boundaries (*), so instruct block placement, etc. to make this
happen. The branch selector has also been adjusted so account for the extra
nops that might now be inserted before loop headers.

(*) Some cores actually prefer other alignments for small loops, but that will
    be addressed in a follow-up commit.

llvm-svn: 225115

1 files changed, 20 insertions, 4 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 32f958ebad7..8d8c32264db 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -679,6 +679,24 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM)
   if (Subtarget.isDarwin())
     setPrefFunctionAlignment(4);
 
+  switch (Subtarget.getDarwinDirective()) {
+  default: break;
+  case PPC::DIR_970:
+  case PPC::DIR_A2:
+  case PPC::DIR_E500mc:
+  case PPC::DIR_E5500:
+  case PPC::DIR_PWR4:
+  case PPC::DIR_PWR5:
+  case PPC::DIR_PWR5X:
+  case PPC::DIR_PWR6:
+  case PPC::DIR_PWR6X:
+  case PPC::DIR_PWR7:
+  case PPC::DIR_PWR8:
+    setPrefFunctionAlignment(4);
+    setPrefLoopAlignment(4);
+    break;
+  }
+
   setInsertFencesForAtomic(true);
 
   if (Subtarget.enableMachineScheduler())
@@ -688,8 +706,8 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM)
 
   computeRegisterProperties();
 
-  // The Freescale cores does better with aggressive inlining of memcpy and
-  // friends. Gcc uses same threshold of 128 bytes (= 32 word stores).
+  // The Freescale cores do better with aggressive inlining of memcpy and
+  // friends. GCC uses same threshold of 128 bytes (= 32 word stores).
   if (Subtarget.getDarwinDirective() == PPC::DIR_E500mc ||
       Subtarget.getDarwinDirective() == PPC::DIR_E5500) {
     MaxStoresPerMemset = 32;
@@ -698,8 +716,6 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM)
     MaxStoresPerMemcpyOptSize = 8;
     MaxStoresPerMemmove = 32;
     MaxStoresPerMemmoveOptSize = 8;
-
-    setPrefFunctionAlignment(4);
   }
 }