[llvm-commits] [llvm] r55422 - /llvm/trunk/lib/Target/X86/X86Instr64bit.td

[Dan Gohman]

Author: djg
Date: Wed Aug 27 12:33:15 2008
New Revision: 55422

URL: http://llvm.org/viewvc/llvm-project?rev=55422&view=rev
Log:
Reinstate the x86-64 portion of r55190. When doing extloads into
64-bit registers from 16-bit and smaller memory locations, prefer
instructions that define the entire 64-bit register, to avoid
partial-register updates.

Modified:
    llvm/trunk/lib/Target/X86/X86Instr64bit.td

Modified: llvm/trunk/lib/Target/X86/X86Instr64bit.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86Instr64bit.td?rev=55422&r1=55421&r2=55422&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86Instr64bit.td (original)
+++ llvm/trunk/lib/Target/X86/X86Instr64bit.td Wed Aug 27 12:33:15 2008
@@ -1254,15 +1254,14 @@
 def : Pat<(zextloadi64i1 addr:$src), (MOVZX64rm8 addr:$src)>;
 
 // extload
-def : Pat<(extloadi64i1 addr:$src),
-          (INSERT_SUBREG (i64 (IMPLICIT_DEF)), (MOV8rm addr:$src),
-                         x86_subreg_8bit)>;
-def : Pat<(extloadi64i8 addr:$src),
-          (INSERT_SUBREG (i64 (IMPLICIT_DEF)), (MOV8rm addr:$src),
-                         x86_subreg_8bit)>;
-def : Pat<(extloadi64i16 addr:$src),
-          (INSERT_SUBREG (i64 (IMPLICIT_DEF)), (MOV16rm addr:$src),
-                         x86_subreg_16bit)>;
+// When extloading from 16-bit and smaller memory locations into 64-bit registers,
+// use zero-extending loads so that the entire 64-bit register is defined, avoiding
+// partial-register updates.
+def : Pat<(extloadi64i1 addr:$src),  (MOVZX64rm8  addr:$src)>;
+def : Pat<(extloadi64i8 addr:$src),  (MOVZX64rm8  addr:$src)>;
+def : Pat<(extloadi64i16 addr:$src), (MOVZX64rm16 addr:$src)>;
+// For other extloads, use subregs, since the high contents of the register are
+// defined after an extload.
 def : Pat<(extloadi64i32 addr:$src),
           (INSERT_SUBREG (i64 (IMPLICIT_DEF)), (MOV32rm addr:$src),
                          x86_subreg_32bit)>;