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

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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 5526c28acc
commit 21c8de8539
3 changed files with 19 additions and 17 deletions
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11
lib/Target/X86/X86InstrInfo.cpp
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@ -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
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
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}"()