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[X86] Prevent folding stack reloads with instructions that have an undefined register update. 

We want to keep the load unfolded so we can use the same register for both sources to avoid a false dependency.

llvm-svn: 334802
This commit is contained in:
Craig Topper 2018-06-15 06:11:36 +00:00
parent 5de2272174
commit 5ec210cc27
3 changed files with 19 additions and 17 deletions
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11
llvm/lib/Target/X86/X86InstrInfo.cpp
View File

@ -8916,12 +8916,15 @@ static bool shouldPreventUndefRegUpdateMemFold(MachineFunction &MF, MachineInstr
if (MF.getFunction().optForSize() || !hasUndefRegUpdate(MI.getOpcode()) ||
!MI.getOperand(1).isReg())
return false;
// Check if the register is explicitly marked as undef.
if (MI.getOperand(1).isUndef())
return true;
// Another possibility is that it is defined by by an IMPLICIT_DEF pseudo.
MachineRegisterInfo &RegInfo = MF.getRegInfo();
MachineInstr *VRegDef = RegInfo.getUniqueVRegDef(MI.getOperand(1).getReg());
if (VRegDef == nullptr)
return false;
return VRegDef->isImplicitDef();
return VRegDef && VRegDef->isImplicitDef()
}

5
llvm/test/CodeGen/X86/break-false-dep.ll
View File

@ -217,7 +217,6 @@ top:
; Make sure we are making a smart choice regarding undef registers and
; hiding the false dependency behind a true dependency
; TODO: We shouldn't be folding the load here.
define double @truedeps(float %arg) {
top:
tail call void asm sideeffect "", "~{xmm6},~{dirflag},~{fpsr},~{flags}"()
@ -228,8 +227,8 @@ top:
%tmp1 = fpext float %arg to double
ret double %tmp1
;AVX-LABEL:@truedeps
;AVX: vxorps [[XMM6:%xmm6]], [[XMM6]], [[XMM6]]
;AVX: vcvtss2sd {{.*}}, [[XMM6]], {{%xmm[0-9]+}}
;AVX-NOT: vxorps
;AVX: vcvtss2sd [[XMM0:%xmm[0-9]+]], [[XMM0]], {{%xmm[0-9]+}}
}
; Make sure we are making a smart choice regarding undef registers and

20
llvm/test/CodeGen/X86/stack-folding-fp-avx1.ll
View File

@ -573,7 +573,7 @@ define i64 @stack_fold_cvtsd2si64_int(<2 x double> %a0) {
}
declare i64 @llvm.x86.sse2.cvtsd2si64(<2 x double>) nounwind readnone
define double @stack_fold_cvtsi2sd(i32 %a0) {
define double @stack_fold_cvtsi2sd(i32 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi2sd
;CHECK: vcvtsi2sdl {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 4-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -581,7 +581,7 @@ define double @stack_fold_cvtsi2sd(i32 %a0) {
ret double %2
}
define <2 x double> @stack_fold_cvtsi2sd_int(i32 %a0) {
define <2 x double> @stack_fold_cvtsi2sd_int(i32 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi2sd_int
;CHECK: vcvtsi2sdl {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 4-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -590,7 +590,7 @@ define <2 x double> @stack_fold_cvtsi2sd_int(i32 %a0) {
}
declare <2 x double> @llvm.x86.sse2.cvtsi2sd(<2 x double>, i32) nounwind readnone
define double @stack_fold_cvtsi642sd(i64 %a0) {
define double @stack_fold_cvtsi642sd(i64 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi642sd
;CHECK: vcvtsi2sdq {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 8-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -598,7 +598,7 @@ define double @stack_fold_cvtsi642sd(i64 %a0) {
ret double %2
}
define <2 x double> @stack_fold_cvtsi642sd_int(i64 %a0) {
define <2 x double> @stack_fold_cvtsi642sd_int(i64 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi642sd_int
;CHECK: vcvtsi2sdq {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 8-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -607,7 +607,7 @@ define <2 x double> @stack_fold_cvtsi642sd_int(i64 %a0) {
}
declare <2 x double> @llvm.x86.sse2.cvtsi642sd(<2 x double>, i64) nounwind readnone
define float @stack_fold_cvtsi2ss(i32 %a0) {
define float @stack_fold_cvtsi2ss(i32 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi2ss
;CHECK: vcvtsi2ssl {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 4-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -615,7 +615,7 @@ define float @stack_fold_cvtsi2ss(i32 %a0) {
ret float %2
}
define <4 x float> @stack_fold_cvtsi2ss_int(i32 %a0) {
define <4 x float> @stack_fold_cvtsi2ss_int(i32 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi2ss_int
;CHECK: vcvtsi2ssl {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 4-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -624,7 +624,7 @@ define <4 x float> @stack_fold_cvtsi2ss_int(i32 %a0) {
}
declare <4 x float> @llvm.x86.sse.cvtsi2ss(<4 x float>, i32) nounwind readnone
define float @stack_fold_cvtsi642ss(i64 %a0) {
define float @stack_fold_cvtsi642ss(i64 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi642ss
;CHECK: vcvtsi2ssq {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 8-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -632,7 +632,7 @@ define float @stack_fold_cvtsi642ss(i64 %a0) {
ret float %2
}
define <4 x float> @stack_fold_cvtsi642ss_int(i64 %a0) {
define <4 x float> @stack_fold_cvtsi642ss_int(i64 %a0) optsize {
;CHECK-LABEL: stack_fold_cvtsi642ss_int
;CHECK: vcvtsi2ssq {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 8-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{rax},~{rbx},~{rcx},~{rdx},~{rsi},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15}"()
@ -1653,7 +1653,7 @@ define <8 x float> @stack_fold_sqrtps_ymm(<8 x float> %a0) {
}
declare <8 x float> @llvm.x86.avx.sqrt.ps.256(<8 x float>) nounwind readnone
define double @stack_fold_sqrtsd(double %a0) {
define double @stack_fold_sqrtsd(double %a0) optsize {
;CHECK-LABEL: stack_fold_sqrtsd
;CHECK: vsqrtsd {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 8-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()
@ -1664,7 +1664,7 @@ declare double @llvm.sqrt.f64(double) nounwind readnone
; TODO stack_fold_sqrtsd_int
define float @stack_fold_sqrtss(float %a0) {
define float @stack_fold_sqrtss(float %a0) optsize {
;CHECK-LABEL: stack_fold_sqrtss
;CHECK: vsqrtss {{-?[0-9]*}}(%rsp), {{%xmm[0-9][0-9]*}}, {{%xmm[0-9][0-9]*}} {{.*#+}} 4-byte Folded Reload
%1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()