[llvm] 1e0500d - [AMDGPU] Consider all SGPR uses as unique in constant bus verify

[Carl Ritson via llvm-commits]

Author: Carl Ritson
Date: 2020-09-24T10:52:40+09:00
New Revision: 1e0500d4f7f19b3eae0f9b6f05591a40188d8d99

URL: https://github.com/llvm/llvm-project/commit/1e0500d4f7f19b3eae0f9b6f05591a40188d8d99
DIFF: https://github.com/llvm/llvm-project/commit/1e0500d4f7f19b3eae0f9b6f05591a40188d8d99.diff

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

Fix the verifier so that overlapping SGPR operands are counted
independently.  We cannot assume that overlapping SGPR accesses
only count as a single constant bus use.
The exception is implicit uses which do not add to constant bus
usage (only) when overlapping.

Reviewed By: rampitec

Differential Revision: https://reviews.llvm.org/D87748

Added: 
    llvm/test/CodeGen/AMDGPU/verify-constant-bus-violations.mir

Modified: 
    llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index 7f06d545602f..344d87f5443d 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3822,11 +3822,7 @@ bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
       ++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 @@ bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
       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 @@ bool SIInstrInfo::verifyInstruction(const MachineInstr &MI,
         }
       }
     }
+
+    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
index 000000000000..317f4125e05a
--- /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
+...