[AArch64] Add new target feature to fuse literal generation

This feature enables the fusion of such operations on Cortex A57, as
recommended in its Software Optimisation Guide, sections 4.14 and 4.15.

Differential revision: https://reviews.llvm.org/D28698

llvm-svn: 293739

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp b/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
index f6d693262c3..7919b681dcb 100644
--- a/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
+++ b/llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
@@ -129,6 +129,31 @@ static bool shouldScheduleAdjacent(const AArch64InstrInfo &TII,
              SecondOpcode == AArch64::INSTRUCTION_LIST_END;
     }
 
+  if (ST.hasFuseLiterals())
+    // Fuse literal generation operations.
+    switch (FirstOpcode) {
+    // PC relative address.
+    case AArch64::ADRP:
+      return SecondOpcode == AArch64::ADDXri ||
+             SecondOpcode == AArch64::INSTRUCTION_LIST_END;
+    // 32 bit immediate.
+    case AArch64::MOVZWi:
+      return (SecondOpcode == AArch64::MOVKWi &&
+              Second->getOperand(3).getImm() == 16) ||
+             SecondOpcode == AArch64::INSTRUCTION_LIST_END;
+    // Lower half of 64 bit immediate.
+    case AArch64::MOVZXi:
+      return (SecondOpcode == AArch64::MOVKXi &&
+              Second->getOperand(3).getImm() == 16) ||
+             SecondOpcode == AArch64::INSTRUCTION_LIST_END;
+    // Upper half of 64 bit immediate.
+    case AArch64::MOVKXi:
+      return First->getOperand(3).getImm() == 32 &&
+             ((SecondOpcode == AArch64::MOVKXi &&
+               Second->getOperand(3).getImm() == 48) ||
+              SecondOpcode == AArch64::INSTRUCTION_LIST_END);
+    }
+
   return false;
 }