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Avoid storing and reloading zeros and other constants from stack slots

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by flagging the associated instructions as being trivially rematerializable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41775 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2007-09-07 21:32:51 +00:00
parent cdd509aecd
commit 1ab79897e2
4 changed files with 22 additions and 2 deletions
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2
lib/Target/X86/X86InstrInfo.td
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@ -2313,6 +2313,7 @@ def CDQ : I<0x99, RawFrm, (outs), (ins),
// Alias instructions that map movr0 to xor.
// FIXME: remove when we can teach regalloc that xor reg, reg is ok.
let isReMaterializable = 1 in {
def MOV8r0 : I<0x30, MRMInitReg, (outs GR8 :$dst), (ins),
"xor{b}\t$dst, $dst",
[(set GR8:$dst, 0)]>;
@ -2322,6 +2323,7 @@ def MOV16r0 : I<0x31, MRMInitReg, (outs GR16:$dst), (ins),
def MOV32r0 : I<0x31, MRMInitReg, (outs GR32:$dst), (ins),
"xor{l}\t$dst, $dst",
[(set GR32:$dst, 0)]>;
}
// Basic operations on GR16 / GR32 subclasses GR16_ and GR32_ which contains only
// those registers that have GR8 sub-registers (i.e. AX - DX, EAX - EDX).

2
lib/Target/X86/X86InstrSSE.td
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@ -399,6 +399,7 @@ def Int_COMISSrm: PSI<0x2F, MRMSrcMem, (outs), (ins VR128:$src1, f128mem:$src2),
// start with 'Fs'.
// Alias instructions that map fld0 to pxor for sse.
let isReMaterializable = 1 in
def FsFLD0SS : I<0xEF, MRMInitReg, (outs FR32:$dst), (ins),
"pxor\t$dst, $dst", [(set FR32:$dst, fp32imm0)]>,
Requires<[HasSSE1]>, TB, OpSize;
@ -1063,6 +1064,7 @@ def Int_COMISDrm: PDI<0x2F, MRMSrcMem, (outs), (ins VR128:$src1, f128mem:$src2),
// start with 'Fs'.
// Alias instructions that map fld0 to pxor for sse.
let isReMaterializable = 1 in
def FsFLD0SD : I<0xEF, MRMInitReg, (outs FR64:$dst), (ins),
"pxor\t$dst, $dst", [(set FR64:$dst, fpimm0)]>,
Requires<[HasSSE2]>, TB, OpSize;

6
lib/Target/X86/X86InstrX86-64.td
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@ -156,12 +156,14 @@ def REP_STOSQ : RI<0xAB, RawFrm, (outs), (ins), "{rep;stosq|rep stosq}",
def MOV64rr : RI<0x89, MRMDestReg, (outs GR64:$dst), (ins GR64:$src),
"mov{q}\t{$src, $dst|$dst, $src}", []>;
let isReMaterializable = 1 in {
def MOV64ri : RIi64<0xB8, AddRegFrm, (outs GR64:$dst), (ins i64imm:$src),
"movabs{q}\t{$src, $dst|$dst, $src}",
[(set GR64:$dst, imm:$src)]>;
def MOV64ri32 : RIi32<0xC7, MRM0r, (outs GR64:$dst), (ins i64i32imm:$src),
"mov{q}\t{$src, $dst|$dst, $src}",
[(set GR64:$dst, i64immSExt32:$src)]>;
}
let isLoad = 1 in
def MOV64rm : RI<0x8B, MRMSrcMem, (outs GR64:$dst), (ins i64mem:$src),
@ -990,13 +992,13 @@ def PsMOVZX64rm32: I<0x8B, MRMSrcMem, (outs GR64:$dst), (ins i32mem:$src),
// FIXME: remove when we can teach regalloc that xor reg, reg is ok.
// FIXME: AddedComplexity gives MOV64r0 a higher priority than MOV64ri32. Remove
// when we have a better way to specify isel priority.
let AddedComplexity = 1 in
let AddedComplexity = 1, isReMaterializable = 1 in
def MOV64r0 : RI<0x31, MRMInitReg, (outs GR64:$dst), (ins),
"xor{q}\t$dst, $dst",
[(set GR64:$dst, 0)]>;
// Materialize i64 constant where top 32-bits are zero.
let AddedComplexity = 1 in
let AddedComplexity = 1, isReMaterializable = 1 in
def MOV64ri64i32 : Ii32<0xB8, AddRegFrm, (outs GR64:$dst), (ins i64i32imm:$src),
"mov{l}\t{$src, ${dst:subreg32}|${dst:subreg32}, $src}",
[(set GR64:$dst, i64immZExt32:$src)]>;

14
test/CodeGen/X86/zero-remat.ll Normal file
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@ -0,0 +1,14 @@
; RUN: llvm-as < %s | llc -march=x86-64 | grep xor | count 4
; RUN: llvm-as < %s | llc -march=x86-64 -stats -info-output-file - | grep asm-printer | grep 12
declare void @bar(double %x)
declare void @barf(float %x)
define double @foo() {
call void @bar(double 0.0)
ret double 0.0
}
define float @foof() {
call void @barf(float 0.0)
ret float 0.0
}