[PATCH] D114843: [X86] Insert FMUL for estimated non reciprocal SQRT when `RefinementSteps` = 0

[Phoebe Wang via Phabricator via llvm-commits]

pengfei created this revision.
pengfei added reviewers: craig.topper, spatel, RKSimon, LuoYuanke, LiuChen3.
Herald added a subscriber: hiraditya.
pengfei requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114843

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/sqrt-fastmath.ll


Index: llvm/test/CodeGen/X86/sqrt-fastmath.ll
===================================================================
--- llvm/test/CodeGen/X86/sqrt-fastmath.ll
+++ llvm/test/CodeGen/X86/sqrt-fastmath.ll
@@ -388,6 +388,7 @@
 ; SSE-LABEL: f32_estimate2:
 ; SSE:       # %bb.0:
 ; SSE-NEXT:    rsqrtss %xmm0, %xmm1
+; SSE-NEXT:    mulss %xmm0, %xmm1
 ; SSE-NEXT:    andps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
 ; SSE-NEXT:    cmpltss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
 ; SSE-NEXT:    andnps %xmm1, %xmm0
@@ -395,15 +396,17 @@
 ;
 ; AVX1-LABEL: f32_estimate2:
 ; AVX1:       # %bb.0:
-; AVX1-NEXT:    vandps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm1
-; AVX1-NEXT:    vrsqrtss %xmm0, %xmm0, %xmm0
-; AVX1-NEXT:    vcmpltss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm1, %xmm1
+; AVX1-NEXT:    vrsqrtss %xmm0, %xmm0, %xmm1
+; AVX1-NEXT:    vandps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm2
+; AVX1-NEXT:    vmulss %xmm1, %xmm0, %xmm0
+; AVX1-NEXT:    vcmpltss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm2, %xmm1
 ; AVX1-NEXT:    vandnps %xmm0, %xmm1, %xmm0
 ; AVX1-NEXT:    retq
 ;
 ; AVX512-LABEL: f32_estimate2:
 ; AVX512:       # %bb.0:
 ; AVX512-NEXT:    vrsqrtss %xmm0, %xmm0, %xmm1
+; AVX512-NEXT:    vmulss %xmm1, %xmm0, %xmm1
 ; AVX512-NEXT:    vbroadcastss {{.*#+}} xmm2 = [NaN,NaN,NaN,NaN]
 ; AVX512-NEXT:    vandps %xmm2, %xmm0, %xmm0
 ; AVX512-NEXT:    vcmpltss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %k1
@@ -481,6 +484,7 @@
 ; SSE-LABEL: v4f32_estimate2:
 ; SSE:       # %bb.0:
 ; SSE-NEXT:    rsqrtps %xmm0, %xmm2
+; SSE-NEXT:    mulps %xmm0, %xmm2
 ; SSE-NEXT:    andps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
 ; SSE-NEXT:    movaps {{.*#+}} xmm1 = [1.17549435E-38,1.17549435E-38,1.17549435E-38,1.17549435E-38]
 ; SSE-NEXT:    cmpleps %xmm0, %xmm1
@@ -490,21 +494,23 @@
 ;
 ; AVX1-LABEL: v4f32_estimate2:
 ; AVX1:       # %bb.0:
-; AVX1-NEXT:    vandps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm1
-; AVX1-NEXT:    vmovaps {{.*#+}} xmm2 = [1.17549435E-38,1.17549435E-38,1.17549435E-38,1.17549435E-38]
-; AVX1-NEXT:    vcmpleps %xmm1, %xmm2, %xmm1
-; AVX1-NEXT:    vrsqrtps %xmm0, %xmm0
+; AVX1-NEXT:    vrsqrtps %xmm0, %xmm1
+; AVX1-NEXT:    vandps {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm2
+; AVX1-NEXT:    vmulps %xmm1, %xmm0, %xmm0
+; AVX1-NEXT:    vmovaps {{.*#+}} xmm1 = [1.17549435E-38,1.17549435E-38,1.17549435E-38,1.17549435E-38]
+; AVX1-NEXT:    vcmpleps %xmm2, %xmm1, %xmm1
 ; AVX1-NEXT:    vandps %xmm0, %xmm1, %xmm0
 ; AVX1-NEXT:    retq
 ;
 ; AVX512-LABEL: v4f32_estimate2:
 ; AVX512:       # %bb.0:
-; AVX512-NEXT:    vbroadcastss {{.*#+}} xmm1 = [NaN,NaN,NaN,NaN]
-; AVX512-NEXT:    vandps %xmm1, %xmm0, %xmm1
+; AVX512-NEXT:    vrsqrtps %xmm0, %xmm1
+; AVX512-NEXT:    vmulps %xmm1, %xmm0, %xmm1
+; AVX512-NEXT:    vbroadcastss {{.*#+}} xmm2 = [NaN,NaN,NaN,NaN]
+; AVX512-NEXT:    vandps %xmm2, %xmm0, %xmm0
 ; AVX512-NEXT:    vbroadcastss {{.*#+}} xmm2 = [1.17549435E-38,1.17549435E-38,1.17549435E-38,1.17549435E-38]
-; AVX512-NEXT:    vcmpleps %xmm1, %xmm2, %xmm1
-; AVX512-NEXT:    vrsqrtps %xmm0, %xmm0
-; AVX512-NEXT:    vandps %xmm0, %xmm1, %xmm0
+; AVX512-NEXT:    vcmpleps %xmm0, %xmm2, %xmm0
+; AVX512-NEXT:    vandps %xmm1, %xmm0, %xmm0
 ; AVX512-NEXT:    retq
   %sqrt = tail call fast <4 x float> @llvm.sqrt.v4f32(<4 x float> %x)
   ret <4 x float> %sqrt
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23228,7 +23228,10 @@
     UseOneConstNR = false;
     // There is no FSQRT for 512-bits, but there is RSQRT14.
     unsigned Opcode = VT == MVT::v16f32 ? X86ISD::RSQRT14 : X86ISD::FRSQRT;
-    return DAG.getNode(Opcode, DL, VT, Op);
+    SDValue Estimate = DAG.getNode(Opcode, DL, VT, Op);
+    if (RefinementSteps == 0 && !Reciprocal)
+      Estimate = DAG.getNode(ISD::FMUL, DL, VT, Op, Estimate);
+    return Estimate;
   }
 
   if (VT.getScalarType() == MVT::f16 && isTypeLegal(VT) &&


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