[PATCH] D87748: [AMDGPU] Consider all SGPR uses as unique in constant bus verify

[Carl Ritson via Phabricator via llvm-commits]

critson updated this revision to Diff 292458.
critson added a comment.

Add basic test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87748/new/

https://reviews.llvm.org/D87748

Files:
  llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
  llvm/test/CodeGen/AMDGPU/constant-bus-violations.mir


Index: llvm/test/CodeGen/AMDGPU/constant-bus-violations.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/constant-bus-violations.mir
@@ -0,0 +1,15 @@
+# XFAIL: *
+# RUN: llc -march=amdgcn -mcpu=gfx900 -run-pass machineverifier -o - %s | FileCheck -check-prefix=GCN %s
+
+# GCN-LABEL: name: sgpr_reuse
+# GCN: $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, -1, killed $sgpr0_sgpr1, implicit $exec
+---
+name:           sgpr_reuse
+liveins:
+  - { reg: '$sgpr0_sgpr1', virtual-reg: '' }
+body:            |
+  bb.0:
+    liveins: $sgpr0_sgpr1
+    $vgpr0 = V_CNDMASK_B32_e64 0, $sgpr0, 0, -1, killed $sgpr0_sgpr1, implicit $exec
+...
+
Index: llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3820,11 +3820,7 @@
       ++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)
@@ -3833,8 +3829,8 @@
       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);
@@ -3845,6 +3841,18 @@
         }
       }
     }
+
+    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) &&


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