AMDGPU: IMPLICIT_DEFs and DBG_VALUEs do not contribute to wait states

Summary:
This fixes a bug that was exposed on gfx9 in various
GL45-CTS.shaders.loops.*_iterations.select_iteration_count_fragment tests,
e.g. GL45-CTS.shaders.loops.do_while_uniform_iterations.select_iteration_count_fragment

Reviewers: arsenm

Subscribers: kzhuravl, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D36193

llvm-svn: 312337

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
index b601cfeded1..400c4aae9e0 100644
--- a/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
@@ -218,12 +218,17 @@ void GCNHazardRecognizer::RecedeCycle() {
 
 int GCNHazardRecognizer::getWaitStatesSince(
     function_ref<bool(MachineInstr *)> IsHazard) {
-  int WaitStates = -1;
+  int WaitStates = 0;
   for (MachineInstr *MI : EmittedInstrs) {
+    if (MI) {
+      if (IsHazard(MI))
+        return WaitStates;
+
+      unsigned Opcode = MI->getOpcode();
+      if (Opcode == AMDGPU::DBG_VALUE || Opcode == AMDGPU::IMPLICIT_DEF)
+        continue;
+    }
     ++WaitStates;
-    if (!MI || !IsHazard(MI))
-      continue;
-    return WaitStates;
   }
   return std::numeric_limits<int>::max();
 }