Teach the code generator that shrd/shld is commutable if it has an immediate.
This allows us to generate this:
foo:
mov %EAX, DWORD PTR [%ESP + 4]
mov %EDX, DWORD PTR [%ESP + 8]
shld %EDX, %EDX, 2
shl %EAX, 2
ret
instead of this:
foo:
mov %EAX, DWORD PTR [%ESP + 4]
mov %ECX, DWORD PTR [%ESP + 8]
mov %EDX, %EAX
shrd %EDX, %ECX, 30
shl %EAX, 2
ret
Note the magically transmogrifying immediate.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19686 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86InstrInfo.h b/lib/Target/X86/X86InstrInfo.h
index c8f8716..f185569 100644
--- a/lib/Target/X86/X86InstrInfo.h
+++ b/lib/Target/X86/X86InstrInfo.h
@@ -191,6 +191,12 @@
///
virtual MachineInstr *convertToThreeAddress(MachineInstr *TA) const;
+ /// commuteInstruction - We have a few instructions that must be hacked on to
+ /// commute them.
+ ///
+ virtual MachineInstr *commuteInstruction(MachineInstr *MI) const;
+
+
/// Insert a goto (unconditional branch) sequence to TMBB, at the
/// end of MBB
virtual void insertGoto(MachineBasicBlock& MBB,