diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3822,11 +3822,7 @@
       ++ConstantBusCount;
 
     SmallVector<Register, 2> SGPRsUsed;
-    Register SGPRUsed = findImplicitSGPRRead(MI);
-    if (SGPRUsed != AMDGPU::NoRegister) {
-      ++ConstantBusCount;
-      SGPRsUsed.push_back(SGPRUsed);
-    }
+    Register SGPRUsed;
 
     for (int OpIdx : OpIndices) {
       if (OpIdx == -1)
@@ -3835,8 +3831,8 @@
       if (usesConstantBus(MRI, MO, MI.getDesc().OpInfo[OpIdx])) {
         if (MO.isReg()) {
           SGPRUsed = MO.getReg();
-          if (llvm::all_of(SGPRsUsed, [this, SGPRUsed](unsigned SGPR) {
-                return !RI.regsOverlap(SGPRUsed, SGPR);
+          if (llvm::all_of(SGPRsUsed, [SGPRUsed](unsigned SGPR) {
+                return SGPRUsed != SGPR;
               })) {
             ++ConstantBusCount;
             SGPRsUsed.push_back(SGPRUsed);
@@ -3847,6 +3843,18 @@
         }
       }
     }
+
+    SGPRUsed = findImplicitSGPRRead(MI);
+    if (SGPRUsed != AMDGPU::NoRegister) {
+      // Implicit uses may safely overlap true overands
+      if (llvm::all_of(SGPRsUsed, [this, SGPRUsed](unsigned SGPR) {
+            return !RI.regsOverlap(SGPRUsed, SGPR);
+          })) {
+        ++ConstantBusCount;
+        SGPRsUsed.push_back(SGPRUsed);
+      }
+    }
+
     // v_writelane_b32 is an exception from constant bus restriction:
     // vsrc0 can be sgpr, const or m0 and lane select sgpr, m0 or inline-const
     if (ConstantBusCount > ST.getConstantBusLimit(Opcode) &&
diff --git a/llvm/test/CodeGen/AMDGPU/verify-constant-bus-violations.mir b/llvm/test/CodeGen/AMDGPU/verify-constant-bus-violations.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/verify-constant-bus-violations.mir
@@ -0,0 +1,27 @@
+# RUN: not --crash llc -march=amdgcn -mcpu=gfx900 -run-pass machineverifier -o /dev/null %s 2>&1 | FileCheck -check-prefix=GFX9-ERR %s
+# RUN: not --crash llc -march=amdgcn -mcpu=gfx1010 -mattr=-wavefrontsize32,+wavefrontsize64 -run-pass machineverifier -o /dev/null %s 2>&1 | FileCheck -check-prefix=GFX10-ERR %s
+
+# GFX9-ERR: *** Bad machine code: VOP* instruction violates constant bus restriction ***
+# GFX9-ERR: $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, -1, killed $sgpr0_sgpr1, implicit $exec
+---
+name:           sgpr_reuse_2sgpr
+liveins:
+  - { reg: '$sgpr0_sgpr1', virtual-reg: '' }
+body:            |
+  bb.0:
+    liveins: $sgpr0_sgpr1
+    $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, -1, killed $sgpr0_sgpr1, implicit $exec
+...
+
+# GFX10-ERR: *** Bad machine code: VOP* instruction violates constant bus restriction ***
+# GFX10-ERR: $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, $sgpr2, killed $sgpr0_sgpr1, implicit $exec
+---
+name:           sgpr_reuse_3sgpr
+liveins:
+  - { reg: '$sgpr0_sgpr1', virtual-reg: '' }
+  - { reg: '$sgpr2', virtual-reg: '' }
+body:            |
+  bb.0:
+    liveins: $sgpr0_sgpr1, $sgpr2
+    $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, $sgpr2, killed $sgpr0_sgpr1, implicit $exec
+...