[llvm] [AMDGPU] Skip debug instructions when eliminating S_SET_GPR_IDX_ON/OFF (PR #160715)

[Jay Foad via llvm-commits]

https://github.com/jayfoad updated https://github.com/llvm/llvm-project/pull/160715

>From f8311a3b0989b16dd40e99763f392e0896469658 Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Thu, 25 Sep 2025 15:38:58 +0100
Subject: [PATCH 1/3] [AMDGPU] Skip debug instructions when eliminating
 S_SET_GPR_IDX_ON/OFF

---
 llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp      | 2 +-
 llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
index 4d3331ab353d3..96593cf5fb990 100644
--- a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
+++ b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
@@ -299,7 +299,7 @@ bool SIPreEmitPeephole::optimizeSetGPR(MachineInstr &First,
   for (MachineBasicBlock::instr_iterator I = std::next(First.getIterator()),
                                          E = MI.getIterator();
        I != E; ++I) {
-    if (I->isBundle())
+    if (I->isBundle() || I->isDebugInstr())
       continue;
     switch (I->getOpcode()) {
     case AMDGPU::S_SET_GPR_IDX_MODE:
diff --git a/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir b/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
index 002d43f937837..2cb3e9e95ed18 100644
--- a/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
+++ b/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
@@ -1,5 +1,6 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -mtriple=amdgcn -mcpu=gfx900 -run-pass si-pre-emit-peephole -verify-machineinstrs -o - %s | FileCheck -check-prefix=GCN %s -implicit-check-not=S_SET_GPR_IDX
+# RUN: llc -mtriple=amdgcn -mcpu=gfx900 -run-pass si-pre-emit-peephole -verify-machineinstrs -o - %s -debugify-and-strip-all-safe | FileCheck -check-prefix=GCN %s -implicit-check-not=S_SET_GPR_IDX
 # RUN: llc -mtriple=amdgcn -mcpu=gfx900 -passes si-pre-emit-peephole -o - %s | FileCheck -check-prefix=GCN %s -implicit-check-not=S_SET_GPR_IDX
 
 ---

>From 31e1d025844aadf0e89a3341acdc2eea42c74825 Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Thu, 25 Sep 2025 15:52:45 +0100
Subject: [PATCH 2/3] Skip all meta instructions

---
 llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
index 96593cf5fb990..8517586abe6e5 100644
--- a/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
+++ b/llvm/lib/Target/AMDGPU/SIPreEmitPeephole.cpp
@@ -299,7 +299,7 @@ bool SIPreEmitPeephole::optimizeSetGPR(MachineInstr &First,
   for (MachineBasicBlock::instr_iterator I = std::next(First.getIterator()),
                                          E = MI.getIterator();
        I != E; ++I) {
-    if (I->isBundle() || I->isDebugInstr())
+    if (I->isBundle() || I->isMetaInstruction())
       continue;
     switch (I->getOpcode()) {
     case AMDGPU::S_SET_GPR_IDX_MODE:

>From 574f5610a3bb1f3868dce9fafe428b421a6acaaf Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Thu, 25 Sep 2025 16:26:59 +0100
Subject: [PATCH 3/3] Test KILL

---
 .../CodeGen/AMDGPU/set-gpr-idx-peephole.mir   | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir b/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
index 2cb3e9e95ed18..2e1f8b4458b13 100644
--- a/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
+++ b/llvm/test/CodeGen/AMDGPU/set-gpr-idx-peephole.mir
@@ -41,6 +41,25 @@ body:             |
   S_SET_GPR_IDX_OFF implicit-def $mode, implicit $mode
 ...
 
+---
+name:            kill_in_between
+body:             |
+  bb.0:
+    ; GCN-LABEL: name: kill_in_between
+    ; GCN: S_SET_GPR_IDX_ON $sgpr2, 1, implicit-def $m0, implicit-def $mode, implicit undef $m0, implicit $mode
+    ; GCN-NEXT: $vgpr16 = V_MOV_B32_indirect_read undef $vgpr1, implicit $exec, implicit $m0, implicit $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7_vgpr8_vgpr9_vgpr10_vgpr11_vgpr12_vgpr13_vgpr14_vgpr15
+    ; GCN-NEXT: KILL $sgpr0
+    ; GCN-NEXT: $vgpr15 = V_MOV_B32_indirect_read undef $vgpr0, implicit $exec, implicit $m0, implicit killed $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7_vgpr8_vgpr9_vgpr10_vgpr11_vgpr12_vgpr13_vgpr14_vgpr15
+    ; GCN-NEXT: S_SET_GPR_IDX_OFF implicit-def $mode, implicit $mode
+  S_SET_GPR_IDX_ON $sgpr2, 1, implicit-def $m0, implicit-def $mode, implicit undef $m0, implicit $mode
+  $vgpr16 = V_MOV_B32_indirect_read undef $vgpr1, implicit $exec, implicit $m0, implicit $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7_vgpr8_vgpr9_vgpr10_vgpr11_vgpr12_vgpr13_vgpr14_vgpr15
+  S_SET_GPR_IDX_OFF implicit-def $mode, implicit $mode
+  KILL $sgpr0
+  S_SET_GPR_IDX_ON killed $sgpr2, 1, implicit-def $m0, implicit-def $mode, implicit undef $m0, implicit $mode
+  $vgpr15 = V_MOV_B32_indirect_read undef $vgpr0, implicit $exec, implicit $m0, implicit killed $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7_vgpr8_vgpr9_vgpr10_vgpr11_vgpr12_vgpr13_vgpr14_vgpr15
+  S_SET_GPR_IDX_OFF implicit-def $mode, implicit $mode
+...
+
 ---
 name:            valu_write_in_between
 body:             |