diff options
| -rw-r--r-- | lib/Target/X86/X86Instr64bit.td | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/lib/Target/X86/X86Instr64bit.td b/lib/Target/X86/X86Instr64bit.td index a1706a8144..93cd0c498b 100644 --- a/lib/Target/X86/X86Instr64bit.td +++ b/lib/Target/X86/X86Instr64bit.td @@ -1254,15 +1254,14 @@ def : Pat<(i64 (zext GR32:$src)), def : Pat<(zextloadi64i1 addr:$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)>; |