AMDGPU/InsertWaitcnts: Update VGPR/SGPR bounds when brackets are merged

Summary:
Fix an issue where VGPR/SGPR bounds are not properly extended when brackets are merged.
This manifests as missing waitcnt insertions when multiple brackets are forwarded to a successor block and the first forward has lower VGPR/SGPR bounds.

Irreducible loop test has been extended based on a CTS failure detected for GFX9.

Reviewers: nhaehnle

Reviewed By: nhaehnle

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

Differential Revision: https://reviews.llvm.org/D55602

llvm-svn: 349611

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
index 79674046fce..afc0b446761 100644
--- a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
@@ -1216,6 +1216,9 @@ bool WaitcntBrackets::merge(const WaitcntBrackets &Other) {
       StrictDom = true;
   }
 
+  VgprUB = std::max(getMaxVGPR(), Other.getMaxVGPR());
+  SgprUB = std::max(getMaxSGPR(), Other.getMaxSGPR());
+
   return StrictDom;
 }