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[ARM] Do not fuse VADD and VMUL on the Cortex-M4 and Cortex-M33 

A sequence of VMUL and VADD instructions always give the same or better
performance than a fused VMLA instruction on the Cortex-M4 and Cortex-M33.
Executing the VMUL and VADD back-to-back requires the same cycles, but
having separate instructions allows scheduling to avoid the hazard between
these 2 instructions.

Differential Revision: https://reviews.llvm.org/D52289

llvm-svn: 342874
This commit is contained in:
Sjoerd Meijer 2018-09-24 12:02:50 +00:00
parent 5555c00902
commit d986ede313
4 changed files with 26 additions and 6 deletions
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2
llvm/lib/Target/ARM/ARM.td
View File

@ -966,6 +966,7 @@ def : ProcessorModel<"cortex-m4", CortexM3Model, [ARMv7em,
FeatureVFPOnlySP,
FeatureD16,
FeaturePrefLoopAlign32,
FeatureHasSlowFPVMLx,
FeatureHasNoBranchPredictor]>;
def : ProcNoItin<"cortex-m7", [ARMv7em,
@ -981,6 +982,7 @@ def : ProcessorModel<"cortex-m33", CortexM3Model, [ARMv8mMainline,
FeatureD16,
FeatureVFPOnlySP,
FeaturePrefLoopAlign32,
FeatureHasSlowFPVMLx,
FeatureHasNoBranchPredictor]>;
def : ProcNoItin<"cortex-a32", [ARMv8a,

6
llvm/lib/Target/ARM/ARMInstrInfo.td
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@ -353,10 +353,10 @@ def UseNegativeImmediates :
let RecomputePerFunction = 1 in {
def UseMovt : Predicate<"Subtarget->useMovt(*MF)">;
def DontUseMovt : Predicate<"!Subtarget->useMovt(*MF)">;
def UseMovtInPic : Predicate<"Subtarget->useMovt(*MF) && Subtarget->allowPositionIndependentMovt()">;
def DontUseMovtInPic : Predicate<"!Subtarget->useMovt(*MF) || !Subtarget->allowPositionIndependentMovt()">;
def UseMovtInPic : Predicate<"Subtarget->useMovt(*MF) && Subtarget->allowPositionIndependentMovt()">;
def DontUseMovtInPic : Predicate<"!Subtarget->useMovt(*MF) || !Subtarget->allowPositionIndependentMovt()">;
def UseFPVMLx : Predicate<"Subtarget->useFPVMLx() || MF->getFunction().optForMinSize()">;
}
def UseFPVMLx : Predicate<"Subtarget->useFPVMLx()">;
def UseMulOps : Predicate<"Subtarget->useMulOps()">;
// Prefer fused MAC for fp mul + add over fp VMLA / VMLS if they are available.

19
llvm/test/CodeGen/ARM/fmacs.ll
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@ -3,6 +3,8 @@
; RUN: llc -mtriple=arm-eabi -mcpu=cortex-a8 %s -o - | FileCheck %s -check-prefix=A8
; RUN: llc -mtriple=arm-eabi -mcpu=cortex-a9 %s -o - | FileCheck %s -check-prefix=A9
; RUN: llc -mtriple=arm-linux-gnueabi -mcpu=cortex-a9 -float-abi=hard %s -o - | FileCheck %s -check-prefix=HARD
; RUN: llc -mtriple=arm-linux-gnueabi -mcpu=cortex-m4 -float-abi=hard %s -o - | FileCheck %s -check-prefix=VMLA
; RUN: llc -mtriple=arm-linux-gnueabi -mcpu=cortex-m33 -float-abi=hard %s -o - | FileCheck %s -check-prefix=VMLA
define float @t1(float %acc, float %a, float %b) {
entry:
@ -15,6 +17,21 @@ entry:
; A8-LABEL: t1:
; A8: vmul.f32
; A8: vadd.f32
; VMLA-LABEL: t1:
; VMLA: vmul.f32
; VMLA-NEXT: vadd.f32
%0 = fmul float %a, %b
%1 = fadd float %acc, %0
ret float %1
}
define float @vlma_minsize(float %acc, float %a, float %b) #0 {
entry:
; VMLA-LABEL: vlma_minsize:
; VLMA: vmla.f32 s0, s1, s2
%0 = fmul float %a, %b
%1 = fadd float %acc, %0
ret float %1
@ -102,3 +119,5 @@ entry:
%3 = fadd float %1, %2
ret float %3
}
attributes #0 = { minsize nounwind optsize }

5
llvm/test/CodeGen/Thumb2/float-intrinsics-float.ll
View File

@ -1,5 +1,6 @@
; RUN: llc < %s -mtriple=thumbv7-none-eabi -mcpu=cortex-m3 | FileCheck %s -check-prefix=CHECK -check-prefix=SOFT -check-prefix=NONE
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-m4 | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=SP -check-prefix=VMLA
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-m4 | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=SP -check-prefix=NO-VMLA
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-m33 | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=SP -check-prefix=NO-VMLA
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-m7 | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=DP -check-prefix=VFP -check-prefix=FP-ARMv8 -check-prefix=VMLA
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-m7 -mattr=+fp-only-sp | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=SP -check-prefix=FP-ARMv8 -check-prefix=VMLA
; RUN: llc < %s -mtriple=thumbv7-none-eabihf -mcpu=cortex-a7 | FileCheck %s -check-prefix=CHECK -check-prefix=HARD -check-prefix=DP -check-prefix=NEON -check-prefix=VFP4 -check-prefix=NO-VMLA
@ -188,8 +189,6 @@ define float @round_f(float %a) {
ret float %1
}
; FIXME: why does cortex-m4 use vmla, while cortex-a7 uses vmul+vadd?
; (these should be equivalent, even the rounding is the same)
declare float @llvm.fmuladd.f32(float %a, float %b, float %c)
define float @fmuladd_f(float %a, float %b, float %c) {
; CHECK-LABEL: fmuladd_f: