From af1accdd860d4e1768a1f56a8651ae4d13445e14 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper@gmail.com>
Date: Sat, 30 May 2020 17:04:56 -0700
Subject: [PATCH] [X86] Teach computeKnownBitsForTargetNode that the upper half
 of X86ISD::MOVQ2DQ is all zero.

---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 6 ++++++
 llvm/test/CodeGen/X86/mmx-cvt.ll        | 2 --
 llvm/test/CodeGen/X86/vec_insert-7.ll   | 7 +------
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 6ebd468..fa1b194 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33402,6 +33402,12 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     }
     break;
   }
+  case X86ISD::MOVQ2DQ: {
+    // Move from MMX to XMM. Upper half of XMM should be 0.
+    if (DemandedElts.countTrailingZeros() >= (NumElts / 2))
+      Known.setAllZero();
+    break;
+  }
   }
 
   // Handle target shuffles.
diff --git a/llvm/test/CodeGen/X86/mmx-cvt.ll b/llvm/test/CodeGen/X86/mmx-cvt.ll
index 339df30..803b3d9 100644
--- a/llvm/test/CodeGen/X86/mmx-cvt.ll
+++ b/llvm/test/CodeGen/X86/mmx-cvt.ll
@@ -298,7 +298,6 @@ define <4 x float> @sitofp_v2i32_v2f32(<1 x i64>*) nounwind {
 ; X86-NEXT:    movq (%eax), %mm0
 ; X86-NEXT:    paddd %mm0, %mm0
 ; X86-NEXT:    movq2dq %mm0, %xmm0
-; X86-NEXT:    movq {{.*#+}} xmm0 = xmm0[0],zero
 ; X86-NEXT:    cvtdq2ps %xmm0, %xmm0
 ; X86-NEXT:    retl
 ;
@@ -307,7 +306,6 @@ define <4 x float> @sitofp_v2i32_v2f32(<1 x i64>*) nounwind {
 ; X64-NEXT:    movq (%rdi), %mm0
 ; X64-NEXT:    paddd %mm0, %mm0
 ; X64-NEXT:    movq2dq %mm0, %xmm0
-; X64-NEXT:    movq {{.*#+}} xmm0 = xmm0[0],zero
 ; X64-NEXT:    cvtdq2ps %xmm0, %xmm0
 ; X64-NEXT:    retq
   %2 = bitcast <1 x i64>* %0 to x86_mmx*
diff --git a/llvm/test/CodeGen/X86/vec_insert-7.ll b/llvm/test/CodeGen/X86/vec_insert-7.ll
index 52d6e7c..e4b9806 100644
--- a/llvm/test/CodeGen/X86/vec_insert-7.ll
+++ b/llvm/test/CodeGen/X86/vec_insert-7.ll
@@ -8,12 +8,7 @@
 define x86_mmx @mmx_movzl(x86_mmx %x) nounwind {
 ; X32-LABEL: mmx_movzl:
 ; X32:       ## %bb.0:
-; X32-NEXT:    movq2dq %mm0, %xmm0
-; X32-NEXT:    movl $32, %eax
-; X32-NEXT:    pinsrd $0, %eax, %xmm0
-; X32-NEXT:    pxor %xmm1, %xmm1
-; X32-NEXT:    pblendw {{.*#+}} xmm1 = xmm0[0,1],xmm1[2,3],xmm0[4,5,6,7]
-; X32-NEXT:    movdq2q %xmm1, %mm0
+; X32-NEXT:    movq LCPI0_0, %mm0
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: mmx_movzl:
-- 
2.7.4