[ARM] Do not fuse VADD and VMUL, continued (2/2)

This is patch 2/2, following up on D53314, and is the functional change
to prevent fusing mul + add sequences into VFMAs.

Differential revision: https://reviews.llvm.org/D53315

llvm-svn: 344683

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 529446c..fc8ed95 100644 (file)
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -365,12 +365,14 @@ let RecomputePerFunction = 1 in {
 def UseMulOps        : Predicate<"Subtarget->useMulOps()">;
 
 // Prefer fused MAC for fp mul + add over fp VMLA / VMLS if they are available.
-// But only select them if more precision in FP computation is allowed.
+// But only select them if more precision in FP computation is allowed, and when
+// they are not slower than a mul + add sequence.
 // Do not use them for Darwin platforms.
 def UseFusedMAC      : Predicate<"(TM.Options.AllowFPOpFusion =="
                                  " FPOpFusion::Fast && "
                                  " Subtarget->hasVFP4()) && "
-                                 "!Subtarget->isTargetDarwin()">;
+                                 "!Subtarget->isTargetDarwin() &&"
+                                 "Subtarget->useFPVMLx()">;
 
 def HasFastVGETLNi32 : Predicate<"!Subtarget->hasSlowVGETLNi32()">;
 def HasSlowVGETLNi32 : Predicate<"Subtarget->hasSlowVGETLNi32()">;

diff --git a/llvm/test/CodeGen/ARM/fusedMAC.ll b/llvm/test/CodeGen/ARM/fusedMAC.ll
index 6f6cdc1..6b92289 100644 (file)
--- a/llvm/test/CodeGen/ARM/fusedMAC.ll
+++ b/llvm/test/CodeGen/ARM/fusedMAC.ll
@@ -1,4 +1,8 @@
 ; RUN: llc < %s -mtriple=armv7-eabi -mattr=+neon,+vfp4 -fp-contract=fast | FileCheck %s
+; RUN: llc < %s -mtriple=arm-arm-eabi -mcpu=cortex-m7  -fp-contract=fast | FileCheck %s
+; RUN: llc < %s -mtriple=arm-arm-eabi -mcpu=cortex-m4  -fp-contract=fast | FileCheck %s -check-prefix=DONT-FUSE
+; RUN: llc < %s -mtriple=arm-arm-eabi -mcpu=cortex-m33 -fp-contract=fast | FileCheck %s -check-prefix=DONT-FUSE
+
 ; Check generated fused MAC and MLS.
 
 define double @fusedMACTest1(double %d1, double %d2, double %d3) {
@@ -12,6 +16,11 @@ define double @fusedMACTest1(double %d1, double %d2, double %d3) {
 define float @fusedMACTest2(float %f1, float %f2, float %f3) {
 ;CHECK-LABEL: fusedMACTest2:
 ;CHECK: vfma.f32
+
+;DONT-FUSE-LABEL: fusedMACTest2:
+;DONT-FUSE:       vmul.f32
+;DONT-FUSE-NEXT:  vadd.f32
+
   %1 = fmul float %f1, %f2
   %2 = fadd float %1, %f3
   ret float %2