[AMDGPU] Fix assertion failure in SIInsertHardClauses

This new pass failed an assertion whenever there were s_nops after the
end of clause.

Differential Revision: https://reviews.llvm.org/D80007

Author: jayfoad

llvm/lib/Target/AMDGPU/SIInsertHardClauses.cpp

@@ -76,7 +76,7 @@ HardClauseType getHardClauseType(const MachineInstr &MI) {
 
   // Don't form VALU clauses. It's not clear what benefit they give, if any.
 
-  // In practice s_nop is the only internal instructions we're likely to see.
+  // In practice s_nop is the only internal instruction we're likely to see.
   // It's safe to treat the rest as illegal.
   if (MI.getOpcode() == AMDGPU::S_NOP)
     return HARDCLAUSE_INTERNAL;
@@ -103,23 +103,25 @@ class SIInsertHardClauses : public MachineFunctionPass {
     // The last non-internal instruction in the clause.
     MachineInstr *Last = nullptr;
     // The length of the clause including any internal instructions in the
-    // middle.
+    // middle or after the end of the clause.
     unsigned Length = 0;
     // The base operands of *Last.
     SmallVector<const MachineOperand *, 4> BaseOps;
   };
 
   bool emitClause(const ClauseInfo &CI, const SIInstrInfo *SII) {
-    assert(CI.Length ==
-           std::distance(CI.First->getIterator(), CI.Last->getIterator()) + 1);
-    if (CI.Length < 2)
+    // Get the size of the clause excluding any internal instructions at the
+    // end.
+    unsigned Size =
+        std::distance(CI.First->getIterator(), CI.Last->getIterator()) + 1;
+    if (Size < 2)
       return false;
-    assert(CI.Length <= 64 && "Hard clause is too long!");
+    assert(Size <= 64 && "Hard clause is too long!");
 
     auto &MBB = *CI.First->getParent();
     auto ClauseMI =
         BuildMI(MBB, *CI.First, DebugLoc(), SII->get(AMDGPU::S_CLAUSE))
-            .addImm(CI.Length - 1);
+            .addImm(Size - 1);
     finalizeBundle(MBB, ClauseMI->getIterator(),
                    std::next(CI.Last->getIterator()));
     return true;

llvm/test/CodeGen/AMDGPU/hard-clauses.mir

@@ -1,6 +1,39 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -march=amdgcn -mcpu=gfx1010 -verify-machineinstrs -run-pass si-insert-hard-clauses %s -o - | FileCheck %s
 
+---
+name: nop1
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $sgpr0_sgpr1
+    ; CHECK-LABEL: name: nop1
+    ; CHECK: liveins: $sgpr0_sgpr1
+    ; CHECK: $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0, 0
+    ; CHECK: S_NOP 2
+    $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0, 0
+    S_NOP 2
+...
+
+---
+name: nop2
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $sgpr0_sgpr1
+    ; CHECK-LABEL: name: nop2
+    ; CHECK: liveins: $sgpr0_sgpr1
+    ; CHECK: BUNDLE implicit-def $sgpr2, implicit-def $sgpr2_lo16, implicit-def $sgpr2_hi16, implicit-def $sgpr3, implicit-def $sgpr3_lo16, implicit-def $sgpr3_hi16, implicit $sgpr0_sgpr1 {
+    ; CHECK:   S_CLAUSE 2
+    ; CHECK:   $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0, 0
+    ; CHECK:   S_NOP 2
+    ; CHECK:   $sgpr3 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 4, 0, 0
+    ; CHECK: }
+    $sgpr2 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 0, 0, 0
+    S_NOP 2
+    $sgpr3 = S_LOAD_DWORD_IMM $sgpr0_sgpr1, 4, 0, 0
+...
+
 ---
 name: long_clause
 tracksRegLiveness: true