VX512] Only look at lower bit in constant scalar masks

for scalar masked instructions only the lower bit of the mask is relevant. so for constant masks we should either do an unmasked operation or no operation, depending on the value of the lower bit.
This patch handles cases where the lower bit is '1'.

Differential Revision: https://reviews.llvm.org/D32805

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302546 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index f0c1e0f..68d1110 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -19021,8 +19021,10 @@ static SDValue getScalarMaskingNode(SDValue Op, SDValue Mask,
                                     SDValue PreservedSrc,
                                     const X86Subtarget &Subtarget,
                                     SelectionDAG &DAG) {
-  if (isAllOnesConstant(Mask))
-    return Op;
+
+  if (auto *MaskConst = dyn_cast<ConstantSDNode>(Mask))
+    if (MaskConst->getZExtValue() & 0x1)
+      return Op;
 
   MVT VT = Op.getSimpleValueType();
   SDLoc dl(Op);

diff --git a/test/CodeGen/X86/avx512-scalar_mask.ll b/test/CodeGen/X86/avx512-scalar_mask.ll
index e8f227b..47c6813 100644 (file)
--- a/test/CodeGen/X86/avx512-scalar_mask.ll
+++ b/test/CodeGen/X86/avx512-scalar_mask.ll
@@ -26,6 +26,7 @@ define <4 x float>@test_var_maskz(<4 x float> %v0, <4 x float> %v1, <4 x float>
   ret < 4 x float> %res
 }
 
+; FIXME: we should just return %xmm0 here.
 define <4 x float>@test_const0_mask(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const0_mask:
 ; CHECK:       ## BB#0:
@@ -36,6 +37,7 @@ define <4 x float>@test_const0_mask(<4 x float> %v0, <4 x float> %v1, <4 x float
   ret < 4 x float> %res
 }
 
+; FIXME: we should zero the lower element of xmm0 and return it.
 define <4 x float>@test_const0_maskz(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const0_maskz:
 ; CHECK:       ## BB#0:
@@ -46,6 +48,7 @@ define <4 x float>@test_const0_maskz(<4 x float> %v0, <4 x float> %v1, <4 x floa
   ret < 4 x float> %res
 }
 
+; FIXME: we should just return %xmm0 here.
 define <4 x float>@test_const2_mask(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const2_mask:
 ; CHECK:       ## BB#0:
@@ -56,6 +59,7 @@ define <4 x float>@test_const2_mask(<4 x float> %v0, <4 x float> %v1, <4 x float
   ret < 4 x float> %res
 }
 
+; FIXME: we should zero the lower element of xmm0 and return it.
 define <4 x float>@test_const2_maskz(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const2_maskz:
 ; CHECK:       ## BB#0:
@@ -87,9 +91,7 @@ define <4 x float>@test_const_allone_maskz(<4 x float> %v0, <4 x float> %v1, <4
 define <4 x float>@test_const_3_mask(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const_3_mask:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    kxnorw %k0, %k0, %k0
-; CHECK-NEXT:    kshiftrw $15, %k0, %k1
-; CHECK-NEXT:    vfmadd213ss %xmm2, %xmm1, %xmm0 {%k1}
+; CHECK-NEXT:    vfmadd213ss %xmm2, %xmm1, %xmm0
 ; CHECK-NEXT:    retq
   %res = call <4 x float> @llvm.x86.avx512.mask.vfmadd.ss(<4 x float> %v0,<4 x float> %v1, <4 x float> %v2,  i8 3, i32 4)
   ret < 4 x float> %res
@@ -98,9 +100,7 @@ define <4 x float>@test_const_3_mask(<4 x float> %v0, <4 x float> %v1, <4 x floa
 define <4 x float>@test_const_3_maskz(<4 x float> %v0, <4 x float> %v1, <4 x float> %v2) {
 ; CHECK-LABEL: test_const_3_maskz:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    kxnorw %k0, %k0, %k0
-; CHECK-NEXT:    kshiftrw $15, %k0, %k1
-; CHECK-NEXT:    vfmadd213ss %xmm2, %xmm1, %xmm0 {%k1} {z}
+; CHECK-NEXT:    vfmadd213ss %xmm2, %xmm1, %xmm0
 ; CHECK-NEXT:    retq
   %res = call <4 x float> @llvm.x86.avx512.maskz.vfmadd.ss(<4 x float> %v0,<4 x float> %v1, <4 x float> %v2,  i8 3, i32 4)
   ret < 4 x float> %res